Prospective evaluation of a subcostal echocardiographic cardiac output measurement in critically ill patients compared with standard transthoracic echocardiography measurement – The Right Way

Prospective evaluation of a subcostal echocardiographic cardiac output measurement in critically ill patients compared with standard transthoracic echocardiography measurement – The Right Way | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Prospective evaluation of a subcostal echocardiographic cardiac output measurement in critically ill patients compared with standard transthoracic echocardiography measurement – The Right Way Thomas Maudhuizon, Zoé Demailly, Charles Fauvel, Fabienne Tamion, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9542115/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract Background Measurement of subcostal cardiac output (CO SC ), using subcostal right ventricular outflow tract velocity-time integral (RVOT SC VTI) and subcostal right ventricular outflow tract diameter (RVOT SC d) remains understudied. Methods The primary objective was to evaluate the agreement between standard cardiac output (CO STD ) and CO SC . Secondary objectives included calculating failure rates for window and CO acquisition, analyzing the correlation between RVOT SC and left ventricular outflow tract velocity-time integral (LVOT VTI), and determining the diagnostic performance of ΔRVOT SC VTI to detect ΔLVOT VTI after passive leg raising (PLR). Results Fifty prospective complete echocardiography were performed. Agreement between CO SC and CO STD was excellent (ICC = 0.91, 95% CI 0.82 to 0.96; p < 0.0001) with a mean difference bias (± limit of agreement) of -0.06 L/min (-1.27 to 1.15). Correlation between RVOT SC VTI and LVOT VTI was strong (r = 0.89, 95% CI 0.78 to 0.93; p < 0.0001). While acoustic window availability was similar, CO SC had a significantly higher measurement failure rate than CO STD (9.2%, 95% CI 5.4 to 13.1; p = 0.01). For fluid responsiveness, the ICC for ΔRVOT SC VTI vs. ΔLVOT VTI after a PLR was 0.86 (95% CI 0.76 to 0.92; p < 0.0001). The area under the curve 0.98 (95% CI 0.95 to 1.00). The optimal threshold for ΔRVOT SC VTI was 12.1% (Youden index), demonstrating identical performance to a 13.04% threshold (sensitivity 92.3%, specificity 97.3%) whereas the > 15.9% threshold yields a sensitivity of 46.2%. Conclusions The CO SC measurement shows reliable performance in critical care compared with CO STD . ΔRVOT SC VTI accurately predicts fluid responsiveness, although measurement failure is more frequent than with the CO STD . Echocardiography Hemodynamic monitoring Cardiac output Fluid responsiveness Subcostal window Intensive Care Unit Right ventricular outflow tract Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Hemodynamic monitoring of cardiac output (CO) is essential for diagnosing shock, identifying its underlying mechanisms and guiding therapy [ 1 ]. Traditionally measured using a pulmonary artery catheter, CO can nowadays be assessed invasively via transpulmonary thermodilution with pulse contour analysis or noninvasively using transthoracic echocardiography (TTE) [ 2 ]. Over the past decade, TTE has become widely available in critical care, providing a reliable, rapid and dynamic tool for CO measurement and cardiovascular assessment across a wide range of clinical conditions and beyond shock [ 3 ]. Using TTE, standard cardiac output (CO STD ) is assessed by measuring both the left ventricular outflow tract diameter (LVOTd) allowing to calculate the LVOT area, obtained from the parasternal long-axis (PLAX) view and the left ventricular outflow tract velocity-time integral (LVOT VTI), obtained from the apical five-chamber (A5C) window [ 4 ]. Multiplying the LVOT area by the LVOT VTI yields the stroke volume (SV) which, when multiplied by heart rate (HR), provides the CO STD . However, acquisition of these echocardiographic parameters can be technically challenging in the intensive care unit (ICU) due to critical illness, invasive mechanical ventilation and positioning limitations [ 5 ]. In this context, the subcostal (SC) echocardiographic window is often preferred in emergency settings [ 6 ], but does not allow reliable assessment of CO. In contrast, the subcostal parasternal short-axis (PSAX SC ) view of the right ventricular outflow tract (RVOT SC ) allows measurement of both the subcostal right ventricular outflow tract diameter (RVOT SC d) and the velocity–time integral (RVOT SC VTI) [ 4 , 7 ]. Since systemic and pulmonary CO are generally considered equivalent, except possibly in moribund patients, subcostal cardiac output (CO SC ) assessment could serve as a reliable surrogate for CO STD . This approach is a promising alternative for CO estimation, with a retrospective study of 30 patients showing good correlation between LVOT VTI and RVOT SC VTI [ 8 ]. Furthermore, in the ICU, passive leg raising (PLR) manoeuvre is commonly used to guide fluid resuscitation [ 9 ]. A change in LVOT VTI (ΔLVOT VTI) ≥ 12% following PLR manoeuvre is well established as a predictor of fluid responsiveness [ 10 , 11 ]. Given that RVOT SC d is not expected to change with PLR – similarly to LVOTd – reliable RVOT SC VTI measurement could serve as an alternative tool to guide fluid management. Recently two prospective studies demonstrated that a change in RVOT SC VTI (ΔRVOT SC VTI) > 15.9% or ≥ 13.04% following PLR manoeuvre could identified preload-responsiveness [ 12 , 13 ]. This prospective study aimed to evaluate the agreement between CO STD and CO SC measurements which has not previously been assessed. The study also focused on the ability of ΔRVOT SC VTI to detect preload-responsiveness. Patients and methods Study design and setting This was a single-center prospective observational study carried out from November 2024 to July 2025 in the medical ICU of Charles Nicolle University Hospital, Rouen, France. The study protocol was registered (NCT07177391) and approved by the Ile de France VII Ethics Committee (2024-A01706-41). The study adhered to the European Society of Intensive Care Medicine (ESICM) recommendations for clinical echocardiography research (PRICES) [ 14 ]. Informed non-opposition was obtained via written information sheets provided to patients, legal representatives or families. Study Objectives The primary objective was to assess the agreement between CO SC and CO STD . Secondary objectives included: 1) determining the mean bias and limits of agreement between CO SC and CO STD ; 2) assessing the feasibility of acoustic window acquisitions, defined as the ability to obtain the predefined echocardiographic windows required for CO measurement in all patients; 3) determining the failure rate of CO measurement, defined as the inability to complete these measurements regardless of initial feasibility status; 4) evaluating the correlation between LVOT VTI and RVOT SC VTI and 5) evaluating the diagnostic performance of ΔRVOT SC VTI following PLR manoeuvre for detecting ≥ 12% ΔLVOT VTI. Participants Adult patients (≥ 18 years) admitted to the ICU were screened for inclusion whenever a TTE was clinically indicated for circulatory failure, dyspnea, hemodynamic monitoring, therapeutic follow-up, volume status assessment, or suspicion of infective endocarditis. Enrolment was non-consecutive, depending on investigator and equipment availability, and a single patient could undergo repeated assessments based on clinical requirements. Patients or their legal representatives who retrospectively opposed data storage or research use were not enrolled. Patients with grade ≥ 3 aortic or pulmonary regurgitation, those unable to undergo the PLR manoeuvre, patients with intracranial hypertension or intra-abdominal hypertension, individuals under legal protection or deprived of liberty, pregnant patients and moribund patients were also excluded. Protocol Echocardiographic measurements Echocardiography was performed using a Vivid S70 (General Electric, Milwaukee, WI, USA) equipped with a 3-MHz 12S-RS cardiac transducer. Following completion of the examination, images and cine loops were exported for analysis. Echocardiographic examinations were performed by a single senior intensivist certified in critical care echocardiography. Standard echocardiographic measurements were performed on parasternal short-axis (PSAX), PLAX, apical 3-chamber, apical 4-chamber, A5C and SC following current guidelines [ 4 ]. According to the guidelines, three measurements were performed for all patients and five in case of atrial fibrillation (AF) [ 3 ]. Valvular diseases were screened and in cases where severe aortic or pulmonary regurgitation was identified or suspected by the investigator, final confirmation was performed through cardiologic assessment. HR was calculated from echocardiographic RR intervals and averaged to the nearest integer. RVOT SC VTI and RVOT SC d were obtained in the same SC view, angled to capture the RVOT and pulmonary artery ( Fig. 1 ) . Measurement quality criteria were extrapolated from LV and RV recommendations [ 4 , 15 ]. When applicable, multiple TTE examinations per patient were sequentially numbered. CO was calculated using HR, SV, ventricular outflow tract diameter (VOTd), and velocity-time integral (VTI) as follow: $$\:CO=\:HR\times\:SV=\:HR\times\:VTI\times\:\pi\:\times\:{\left(\frac{VOTd}{2}\right)}^{2}$$ Passive leg raising and complete examination A complete echocardiographic examination consisted of a baseline assessment which served as the reference procedure [ 4 ]. Then, two consecutive PLR manoeuvres were performed according to guidelines [ 9 ], separated by 2 minutes: the first for CO STD and the second for CO SC ( Fig. 2 ) . For each manoeuvre, parameters were assessed before PLR (t0), at 30 to 60 seconds after PLR (t1 PLR ) and at 1 minute after returning to the baseline position (t2). A positive PLR response for LVOT VTI was defined as a ΔLVOT VTI ≥ 12% based on the least significant change of 12% calculated for a single operator, ensuring the value exceeded measurement noise in the ICU setting [ 16 ] and aligned with established echocardiographic PLR CO variation thresholds [ 9 , 11 ]. Regarding ΔRVOT SC VTI, a higher positivity thresholds of > 15.9% and ≥ 13.04 were also considered in accordance with previous literature [ 12 , 13 ]. Reversibility was assessed by comparing variation in HR and VTI between t0 and t2. Identical thresholds were applied to both intubated and spontaneously breathing patients. All PLR manoeuvres were performed without repositioning the echocardiographic probe or altering catecholamine dosages and ventilator settings [ 9 ]. Data collection In addition to echocardiographic data, clinical data were collected prospectively, including diagnostic parameters, vital signs, relevant medical history, therapies, the Simplified Acute Physiology Score II score [ 17 ], and the Sequential Organ Failure Assessment (SOFA) score [ 18 ]. Statistical analysis Categorical variables were reported as numbers (percentages) and compared using the chi-square test. Continuous variables were reported as mean ± standard deviation or median (interquartile range), as appropriate. Distribution of continuous variables was assessed graphically to limit the multiplicity of formal statistical tests, with the Shapiro-Wilk test applied when non-normality was suspected. Variables were compared using the Student’s t-test or the Mann–Whitney U test, as appropriate. Differences between paired measurements were assessed using the paired Student’s t-test for normally distributed data and the Wilcoxon signed-rank test for non-normally distributed data. Agreement between paired echocardiographic parameters measurement was assessed using intraclass correlation coefficient (ICC) with 95% confidence interval (95% CI). Additional analyses included correlations using Pearson or Spearman analysis as appropriate (r with 95% CI) and assessment of mean bias (± limits of agreement) using Bland-Altman plot. The evaluation of the diagnostic performance of ΔRVOT SC VTI following a PLR for detecting a ≥ 12% ΔLVOT VTI was assessed using Receiver Operating Characteristic (ROC) curves, with calculation of sensitivity, specificity, positive and negative predictive values, likelihood ratios, and area under the curve (AUC) with 95% CI. The number of echocardiographic examinations was calculated based on the primary objective, assuming an ICC, single-measure, absolute agreement of 0.90, an alpha risk of 5%, and with 50 complete examinations (t0, t1 PLR , t2–150 measurements) a resulting power of 93%. Only complete examinations were analyzed for primary objective and the diagnostic performance of ΔRVOT SC VTI following a PLR for detecting a ≥ 12% ΔLVOT VTI. All statistical analyses were performed independently by a statistician, using R software (R Foundation for Statistical Computing, Vienna, Austria). A p-value < 0.05 was considered statistically significant. Results Between November 15, 2024, and July 16, 2025, a total of 849 patients were admitted. Among them, 65 critically ill patients were included, representing 74 echocardiographic examinations. Two patients were excluded due to severe aortic and pulmonary regurgitation (grades 3 and 4, respectively). Feasibility of acoustic window acquisitions and failure rate for cardiac output measurements Of the 63 remaining patients, 72 echocardiographic examinations were performed. Feasibility of window acquisition was 79.2% for the SC and 84.7% for the A5C+PLAX combination, with no significant difference: -5.6% (95% CI -17.0% to 5.9%; p = 0.48). Details for each time point are summarized in Additional file 1 . The overall failure rate for CO measurement was significantly higher for the SC approach compared to the standard method, with 23.1% vs. 13.9% with a difference of 9.2% (95% CI 5.4 to 13.1; p = 0.01). RVOT SC VTI and LVOT VTI did not differ significantly in failure rate (26.4% versus 15.3%; difference 11.1%, 95% CI: -0.2 to 18.6; p = 0.10 (Table 1, Additional file 2) . RVOT SC d acquisition failed significantly more often than LVOTd (25.0% versus 8.3%; difference 16.7%, 95% CI: 5.1-28.2; p = 0.01). Of the 72 echocardiographic examinations performed, 22 were excluded for incomplete data: 21 lacked paired CO measurements and 1 provided only t0 data. This resulted in 50 complete examinations for final analysis, totaling 150 paired CO/VTI measurements (Figure 3) . The mean number of examinations per patient was 1.11 ± 0.36. Study population The 41 included patients (Additional file 3) were predominantly male (sex ratio 2.4), with a median age of 62 (50-69) years and a median body mass index of 23.7 (20.8-26.5) kg/m ² . The mean SAPS II score was 46 ± 2. Shock occurred in 53.7% of patients, 64.1% were mechanically ventilated, and AF was observed in 12.0% of patients. The main echocardiographic characteristics are summarized in Table 2.Agreement of cardiac output measurement The ICC between CO SC and CO STD was excellent with an ICC of 0.91 (95% CI 0.82 to 0.96; p<0.0001) (Figure 4A, Additional file 4A) and the mean bias (± limit of agreement) in CO measurement was -0.06 L/min (-1.27 to 1.15) (Additional file 5) . RVOT SC VTI and LVOT VTI were strongly correlated (r = 0.89; 95% CI: 0.78–0.93; p < 0.0001) (Figure 4B, Additional file 4B) . All individual and overall measurements for RVOT SC VTI, LVOT VTI, CO SC , CO STD , subcostal stroke volume (SV SC ), standard stroke volume (SV STD ), and HR are presented in Table 3 . Analysis of preload-responsiveness in the complete records The ICC for ΔVTI following a PLR was good with an ICC of 0.86 (95% CI 0.76 to 0.92; p < 0.0001) (Figure 5) . HR changes after PLR were minimal and non-significant: 0 bpm (95% CI: -1 to 1; p = 0.64) right-sided, -1 bpm (95% CI: -2 to 0; p = 0.14) left-sided, and 1 bpm (95% CI: -3 to 0; p = 0.12) globally. VTI changes between t0 and t2 were also non significant (LVOT VTI -0.6%, 95% CI: -2.0 to 0.7; p = 0.35; RVOT SC VTI -0.7%, 95% CI: -2.1 to 0.6; p = 0.27). Using a ΔRVOTSC VTI >15.9% threshold, 6 true positives and 7 false negatives were identified among responders, with 36 true negatives and 1 false positive among non-responders. With a ≥ 13.04% threshold, 12 true positives and 1 false negative were detected in responders, with 36 true negatives and 1 false positive in non-responders. (Additional file 6–7 ) . The AUC for ΔRVOT SC VTI to detected ΔLVOT VTI was 0.98 (95% CI 0.95 to 1.00) (Additional file 8) . A ΔRVOT SC VTI > 15.9% detected a ΔLVOT VTI ≥ 12% following a PLR with a sensitivity of 46.2% (95% CI 19.2 to 74.9), a specificity of 97.3% (95% CI 85.8 to 99.9), a positive predictive value 85.7% (95% CI 42.1 to 99.6), a negative predictive value 83.7% (95% CI 69.3 to 93.2), a positive likelihood ratio of 17.1 (95% CI 2.3 to 128.8), a negative likelihood ratio of 0.6 (95% CI 0.3 to 0.9). A ΔRVOT SC VTI ≥ 13.04% yielded a sensitivity of 92.3% (95% CI 64.0 to 99.8), a specificity of 97.3% (95% CI 85.8 to 99.9), a positive predictive value of 92.3% (95% CI 64.0 to 99.8), a negative predictive value of 97.3% (95% CI 85.8 to 99.9), a positive likelihood ratio of 34.2 (95% CI 4.91 to 237.6), a negative likelihood ratio of 0.079 (95% CI 0.012 to 0.520), and an AUC of 0.98 (95% CI 0.95 to 1.00). The optimal ΔRVOT SC VTI threshold determined by the Youden index ( J = 0.90, 95% CI 0.72 to 1.00) was 12.1%, which demonstrated identical diagnostic performance to the ≥ 13.04% threshold (Additional file 9) . Discussion In this exploratory study of applied bedside hemodynamic physiology, CO SC and CO STD demonstrated excellent agreement, supported by a little mean bias between both of the measurement and a strong correlation between RVOT SC and LVOT VTI. High reliability was also observed for ΔVTI measurements following a PLR maneuver. We also identified an optimal threshold of > 12.1% for predicting fluid responsiveness based on ΔRVOT SC VTI. The feasibility of SC acoustic window acquisition was similar to that of the standard A5C + PLAX views, but the overall failure rate for CO SC measurement was higher, due to a lower rate of successful RVOT SC d acquisition. A previous study reported a mean difference of − 5.0 ± 3.8 cm between LVOT VTI and RVOT SC VTI (ICC 0.73; 95% CI: 0.62–0.81) [ 19 ]. Extending these findings, our study is the first to directly assess agreement between CO SC and CO STD . Although RVOT SC VTI was significantly lower than LVOT VTI, this was offset by a larger RVOT SC diameter resulting in preserved equivalence between CO SC and CO STD . Despite the lack of established reference values for RVOT SC measurements, our results are consistent with standard RVOT estimates and international echocardiography guidelines [ 15 , 20 ]. These findings are physiologically coherent: while the subcostal view does not permit reliable LVOT assessment because of poor alignment [ 21 ], it provides an optimal axis for the RVOT [ 22 ]. Prior studies have confirmed the feasibility of RVOT SC VTI acquisition, showing subcostal pulmonary acceleration time comparable to that obtained in the standard PSAX view [ 23 ]. In our cohort, excellent agreement was demonstrated between CO measurements despite respiratory-induced artifacts and pulmonary transit delays [ 24 ], suggesting that rigorous VTI averaging effectively neutralizes these cyclical variations. The SC view demonstrated similar feasibility of acoustic window acquisition compared with the standard A5C + PLAX views, but a lower overall success rate for cardiac output measurement. However, 6.9% of examinations relied exclusively on the SC view because PLAX and/or A5C windows were unobtainable. In settings in which TTE is essential for rapid hemodynamic assessment in shock [ 25 ], this finding is clinically relevant. Given the demonstrated reliability of CO SC and RVOT SC VTI, the SC approach represents a pragmatic alternative when standard views are not accessible, potentially limiting the need for transesophageal echocardiography or invasive monitoring unless otherwise clinically indicated [ 26 ]. Another key advantage of this method is that it requires only a single echocardiographic window. Unlike CO STD , which combines PLAX and A5C views and may increase measurement error and failure in the ICU, the SC window is widely recognized for its accessibility [ 6 ], even during mechanical ventilation [ 7 ]. Given the excellent agreement observed in our heterogeneous ICU cohort – most of whom were intubated and receiving catecholamines – CO SC represents a promising tool for rapid hemodynamic assessment in emergency settings. In our cohort, a ΔRVOT SC VTI threshold of 12.1% for predicting fluid responsiveness demonstrated excellent diagnostic performance. Preload responsiveness was assessed with good correlation between RVOT SC VTI and LVOT VTI measurements across all time points, and importantly, the reversibility of the PLR effect was consistently demonstrated. While ΔRVOT SC VTI following a PLR have been reported previously [ 12 , 13 ], no consensus threshold has been established. The tested threshold is highly consistent with the recently proposed ≥ 13.04% cutoff [ 13 ], which, when applied to our population, yielded comparable diagnostic performance. By contrast, the > 15.9% threshold [ 12 ] showed high specificity but poor sensitivity, likely reflecting methodological differences, as the reference study employed manual leg raising ; a technique now discouraged due to potential sympathetic stimulation and HR-mediated increases in CO [ 9 ]. Importantly, our 12.1% threshold closely approximates the standard ΔLVOT VTI ≥ 12% criterion for fluid responsiveness. Although this requires prospective validation, theoretical considerations based on the CO formula and assuming constant LVOT and RVOT diameters suggest that relative VTI variations on the right ventricle should closely parallel those observed on the left. Several limitations warrant consideration. First, its exploratory, single-center, single-operator design precluded the assessment of inter-observer variability, a known source of bias in bedside echocardiography [ 26 ]. Study findings may have also been influenced by the open-label design, the lack of a centralized core lab, and potential selection bias due to operator and equipment availability. Secondly, while CO STD served as reference, invasive gold standards such as pulmonary artery catheterization or transpulmonary thermodilution with pulse contour analysis remain more accurate for CO and preload-responsiveness assessment in the ICU [ 1 , 27 ]. Because invasive monitoring was available in only four patients, meaningful comparisons were not feasible. Thirdly, the quality of RVOT SC d and RVOT SC VTI acquisition remain important considerations. Although acoustic window feasibility was similar between PLAX+A5C and SC views, the higher failure rate of RVOT SC d compared to LVOTd measurements resulted in a significantly increased risk of unsuccessful CO SC assessment. In practice, prioritizing a reliable RVOT SC VTI measurement may be preferable when RVOT SC d acquisition is suboptimal; alternative methods should be considered when precise CO monitoring is required. Fourthly, comparing RVOT SC VTI and RVOT SC d directly with measurements from the PSAX window would have further strengthened the validity of our approach. To date, only one study has explored this, reporting strong ICC [ 19 ]. Finally, fluid administration was not performed after the PLR in preload-responsive patients and only the ability of ΔRVOT SC VTI to predict ΔLVOT VTI was assessed from a physiological perspective [ 11 ] and these results must be interpreted in the context of these limitations [ 28 ]. Conclusion Echocardiographic CO SC measurement is reliable and demonstrates excellent agreement with the standard TTE CO STD . LVOT and RVOT SC VTI are highly correlated, further supporting the physiological consistency of right- and left-sided echocardiographic measurements. A ΔRVOT SC VTI threshold of 12.1% after PLR showed excellent diagnostic performance for predicting fluid responsiveness. Future studies are required to confirm the utility of CO SC , ideally in comparison with thermodilution-based measurements to strengthen the generalizability of this method. Confirmation of the 12.1% ΔRVOT SC VTI threshold, following PLR, warrants further exploration in larger prospective cohorts. Abbreviations A3C Apical 3-chamber A4C Apical 4-chamber A5C Apical 5-chamber AF Atrial fibrillation AUC Area under the curve CI Confidence interval CO Cardiac output CO SC Subcostal cardiac output CO STD Standard cardiac output ESICM European Society of Intensive Care Medicine HR Heart rate ICC Intraclass correlation coefficient ICU Intensive care unit LV Left ventricular LVOT Left ventricular outflow tract LVOTd Left ventricular outflow tract diameter LVOT VTI Left ventricular outflow tract velocity-time integral PLAX Parasternal long-axis PLR Passive leg raising PSAX Parasternal short-axis PSAX SC Subcostal parasternal short-axis ROC Receiver Operating Characteristic RV Right ventricular RVOT Right ventricular outflow tract RVOT SC Subcostal right ventricular outflow tract RVOT SC d Subcostal right ventricular outflow tract diameter RVOT SC VTI Subcostal right ventricular outflow tract velocity-time integral RVOTd Right ventricular outflow tract diameter SAPS II Simplified Acute Physiology Score II SC Subcostal SOFA Sequential Organ Failure Assessment SV Stroke volume SV SC Subcostal stroke volume SV STD Standard stroke volume TTE Transthoracic echocardiography VOTd Ventricular outflow tract diameter VTI Velocity-time integral ΔLVOT VTI Change in left ventricular outflow tract velocity-time integral ΔRVOT SC VTI Change in subcostal right ventricular outflow tract velocity-time integral ΔVTI Change in velocity-time integral Declarations Ethics approval and consent to participate Approved by the Ile de France VII Ethics Committee (2024-A01706-41). Informed non-opposition was obtained from all participants or their legal representatives. Consent for publication Not applicable Availability of data and materials The datasets used and analyzed during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare that they have no relevant financial or non-financial interests to disclose. Funding None. Authors' contributions TM designed the study. TM and collected the data. CF, FT, JN and DV provided critical revision of the manuscript. All authors read and approved the final manuscript. Acknowledgements Not applicable References Monnet X, Messina A, Greco M, et al (2025) ESICM guidelines on circulatory shock and hemodynamic monitoring 2025. Intensive Care Med. https://doi.org/10.1007/s00134-025-08137-z McLean AS (2016) Echocardiography in shock management. 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Ann Intensive Care 14:122. https://doi.org/10.1186/s13613-024-01356-5 Chew MS, Aissaoui N, Balik M (2023) Echocardiography in shock. Curr Opin Crit Care 29:252–258. https://doi.org/10.1097/MCC.0000000000001041 Bossa MN, Berto A, Garcia-Sineriz I, et al (2025) Impact of interobserver variability of echocardiography derived clinical metrics on sample size estimation in clinical trials. Eur Heart J - Cardiovasc Imaging 26:jeae333.043. https://doi.org/10.1093/ehjci/jeae333.043 Monnet X, Teboul J-L (2017) Transpulmonary thermodilution: advantages and limits. Crit Care Lond Engl 21:147. https://doi.org/10.1186/s13054-017-1739-5 Levitov A, Marik PE (2012) Echocardiographic assessment of preload responsiveness in critically ill patients. Cardiol Res Pract 2012:819696. https://doi.org/10.1155/2012/819696 Tables Table 1: Number and percentage of measurement failures (n = 72). Number of CO STD measurement failures (n, %) 0 1 2 3 Number of CO SC measurement failures (n, %) 0 50 (69.4%) 0 (0.0%) 0 (0.0%) 5 (6.9%) 1 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 2 0 (0.0%) 0 (0.0%) 1 (1.4%) 0 (0.0%) 3 11 (15.4%) 1 (1.4%) 0 (0.0%) 4 (5.6%) Number of LVOT VTI measurement failures (n, %) 0 1 2 3 Number of RVOT SC VTI measurement failures (n, %) 0 50 (69.4%) 0 (0.0%) 0 (0,0%) 5 (6,9%) 1 0 (0.0%) 0 (0.0%) 0 (0,0%) 1 (1.4%) 2 1 (1.4%) 0 (0.0%) 1 (1.4%) 0 (0.0%) 3 10 (13.9%) 1 (1.4%) 1 (1.4%) 2 (2.8%) Number of LVOTd measurement failures (n, %) 0 1 Number of RVOT SC d measurement failures (n, %) 0 52 (72.2%) 4 (5.6%) 1 14 (19.4%) 2 (2.8%) CO SC – Subcostal cardiac output, CO STD Standard cardiac output, LVOT VTI – Left ventricular outflow tract velocity time integral, LVOTd – Left ventricular outflow tract diameter – RVOT SC VTI – Subcostal right ventricular outflow tract velocity time integral, RVOT SC d – Subcostal right ventricular outflow tract diameter, RVOT SC d – Subcostal right ventricular outflow tract diameter. Table 2: Main echocardiographic data at baseline (n = 50). Echocardiographic examination indication Shock diagnosis, n % 15 (30.0%) Hypoxemia, n % 5 (10.0%) Therapeutic monitoring, n % 13 (26.0%) Volume status evaluation, n % 17 (34.0%) LVEF (visual) > 60 %, n % 10 (20.0%) 50 – 60 %, n % 15 (30.0%) 40 – 49 %, n % 11 (22.0%) 30 – 39 %, n % 5 (10.0%) 20 – 29 %, n % 5 (10.0%) < 20 %, n % 4 (8.0%) Left ventricular diastolic function parameters Mitral E/A ratio, median (IQR) 1.1 (0.8–1.4) Mitral E/e' lateral ratio, median (IQR) 5.6 (7.4–10.3) Mitral E-wave deceleration time (ms), median (IQR) 170 (133–213) Mitral S' wave (cm/s), mean ± SD 10.2 ± 2.7 Left atrial volume index (mL/m²), median (IQR) 22.3 (18.9–25.6) Right ventricular function and structural parameters TAPSE (mm), mean ± SD 21 ± 4 Tricuspid S' wave (cm/s), mean ± SD 12.1 ± 2.9 Tricuspid regurgitation peak velocity (TRPV, m/s), median (IQR) 1.8 (0.0–2.5) Pulmonary acceleration time (ms), mean ± SD 104 ± 28 Right atrial area (cm²), median (IQR) 14.9 (11.9–18.6) RV/LV ratio, mean ± SD 0.9 ± 0.2 Left ventricle eccentricity index, median (IQR) 1.0 (1.0–1.1) Inferior vena cava diameter (mm), median (IQR) 20 (17–24) Inferior vena cava respiratory variation (%), median (IQR) 15 (7–31) Estimated systolic pulmonary arterial pressure (mmHg), median (IQR) 19.4 (12.1–32.7) Pericardium Normal 41 (82.0%) Millimetric effusion 8 (16.0%) Centimetric effusion 1 (2.0%) A – mitral A wave, E– mitral E wave, e’ – lateral e’ mitral tissular velocity, LVEF – Left ventricular ejection fraction, RV/LV ratio – Right ventricle/Left ventricle ratio, TAPSE – Tricuspid annular plane systolic excursion. Table 3: Echocardiographic values and differences at each examination time point (n = 150). t0 (n= 50) t1 PLR (n= 50) t2 (n= 50) Global (n= 150) RVOT SC VTI (cm), mean ± SD 15.4 ± 4.5 16.3 ± 4.9 15.5 ± 4.6 15.7 ± 4.7 LVOT VTI (cm), mean ± SD 16.7 ± 5.1 17.7 ± 5.6 16.7 ± 4.9 17.0 ± 5.2 CO SC (L/min), mean ± SD 4.78 ± 1.35 5.05 ± 1.63 4.80 ± 1.46 4.88 ± 1.48 CO STD (L/min), mean ± SD 4.87 ± 1.45 5.11 ± 1.64 4.85 ± 1.44 4.94 ± 1.51 SV SC (mL), mean ± SD 54 ± 18 57 ± 20 55 ± 19 55 ± 19 SV STD (mL), mean ± SD 54 ± 17 57 ± 19 54 ± 16 55 ± 17 HR SC (bpm), median (IQR) 88 (76–111) 88 (74–112) 86 (75–112) 88 (75–112) HR STD (bpm), median (IQR) 88 (75–115) 87 (74–110) 88 (75–111) 88 (75–123) RVOT SC d (mm), median (IQR) 20.8 (20.0–22.3) / / / LVOTd (mm), median (IQR) 20.3 (19.9–21.0) / / / t0 (n= 50) t1 PLR (n= 50) t2 (n= 50) Global (n= 150) VTI difference (cm), IC95% -1.3 (-2.0–-0.7) -1.4 (-2.1– -0.7) -1.2 (-1.7– -0.7) -1.3 (-1.7– -0.9) p < 0.0001 p < 0.0001 p < 0.0001 p < 0.0001 CO difference (L/min), IC95% -0.08 (-0.24–0.07) -0.05 (-0.23–0.12) -0.05 (-0.24–0.14) -0.06 (-0.19–0.05) p = 0.285 p = 0.545 p = 0.594 p = 0.242 SV difference (mL), IC95% 0 (-2–2) 0 (-2–2) 0 (-2–3) 0 (-2–2) p = 0.973 p = 0.949 p = 0.615 p = 0.834 HR difference (bpm), IC95% 0 (-2–2) 0 (-2–3) -1 (-4–2) 0 (-2–2) p = 0.546 p = 1.000 p = 0.247 p = 0.312 VOTd difference (mm), IC95% 0.7 (0.3–1.4) / / / p = 0.002 / / / CO – Cardiac output, CO SC – Subcostal cardiac output, CO STD Standard cardiac output, HR SC – heart rate during subcostal measurement, HR STD – heart rate during standard measurement, LVOT VTI – Left ventricular outflow tract velocity time integral, LVOTd – Left ventricular outflow tract diameter, RVOT SC VTI – Subcostal right ventricular outflow tract velocity time integral, RVOT SC d – Subcostal right ventricular outflow tract diameter, SV – Stroke volume, SV SC – right subcostal stroke volume, SV STD – Standard stroke volume, VOTd– Ventricular outflow tract diameter, VTI – Velocity time integral Additional Declarations No competing interests reported. Supplementary Files AdditionalFile1.pdf Additional file 1: Feasibility (%) of obtaining the required echocardiographic windows (n = 72). (A5C – Apical 5-chamber window, PLAX – Parasternal long-axis window, SC – subcostal window, t0 – baseline measurement before PLR, t1 PLR – measurement 30 to 60 seconds after passive leg raising, t2 – measurement 60 seconds after returning to baseline.) AdditionalFile2.pdf Additional file 2: Failure rates (%) for cardiac output-related echocardiographic parameters (n = 72). (CO SC – Subcostal cardiac output, CO STD Standard cardiac output, LVOT VTI – Left ventricular outflow tract velocity time integral, RVOT SC VTI – Subcostal right ventricular outflow tract velocity time integral, t0 – baseline measurement before PLR, t1 PLR – measurement 30 to 60 seconds after passive leg raising, t2 – measurement 60 seconds after returning to baseline.) AdditionalFile3.pdf Additional file 3: Patient characteristics and clinical status at complete echocardiographic examination (ARDS – Acute respiratory distress syndrome, BMI – Body Mass Index, FiO 2 – Fraction of inspired oxygen, IQR – Interquartile range, NIV – Non-invasive ventilation, PEEP – Positive end-expiratory pressure, SAPS II – Simplified Acute Physiology Score II.) AdditionalFile4.pdf Additional file 4: A: Scatter plots representing paired CO SC and CO STD at t0, t1 PLR , and t2. B: Scatter plots representing paired RVOT SC VTI and LVOT VTI at t0, t1 PLR , and t2. Each color corresponds to a different patient, and dashed arrows indicate the trajectory of CO and VTI variations over time (from t0 to t1 PLR , and from t1 PLR to t2). (CO SC – Subcostal cardiac output, CO STD – Standard cardiac output, LVOT VTI – Left ventricular outflow tract velocity time integral, PLR – passive leg raising, RVOT SC VTI – Subcostal right ventricular outflow tract velocity time integral, t0 – baseline measurement before PLR, t1 PLR – measurement 30 to 60 seconds after passive leg raisig, t2 – measurement 60 seconds after returning to baseline.) AdditionalFile5.pdf Additional file 5: Bland-Altman plot between CO SC and CO STD (L/min). (CO SC – Subcostal cardiac output, CO STD – Standard cardiac output, SD – Standard deviation.) AdditionalFile6.pdf Additional file 6: Contingency table of diagnostic performance of ΔRVOTSC VTI >15.9% to detect ΔLVOT VTI ≥ 12% following a PLR (n = 50) (ΔLVOT VTI – variation of left ventricular outflow tract velocity time integral, ΔRVOT SC VTI variation of subcostal right ventricular outflow tract velocity time integral, PLR – Passive leg raising). AdditionalFile7.pdf Additional file 7: Contingency table of diagnostic performance of ΔRVOT SC VTI ≥ 13.04% to detect ΔLVOT VTI ≥ 12% following a PLR (n = 50) (ΔLVOT VTI – variation of left ventricular outflow tract velocity time integral, ΔRVOT SC VTI variation of subcostal right ventricular outflow tract velocity time integral, PLR – Passive leg raising). AdditionalFile8.pdf Additional file 8: ROC curves for ΔRVOT SC VTI to detect ΔLVOT VTI following a PLR. (AUC – Area under the curve, ROC – Receiver operating characteristic, ΔLVOT VTI – Variation of left ventricular outflow tract velocity time integral, ΔRVOT SC VTI – Variation of subcostal right ventricular outflow tract velocity time integral, PLR – Passive leg raising). AdditionalFile9.pdf Additional file 9: Contingency table of diagnostic performance of ΔRVOT SC VTI > 12.01% to detect ΔLVOT VTI ≥ 12% following a PLR (n = 50) (ΔLVOT VTI – variation of left ventricular outflow tract velocity time integral, ΔRVOT SC VTI variation of subcostal right ventricular outflow tract velocity time integral, PLR – Passive leg raising). Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 16 May, 2026 Reviews received at journal 02 May, 2026 Reviewers agreed at journal 01 May, 2026 Reviewers invited by journal 01 May, 2026 Editor assigned by journal 29 Apr, 2026 Submission checks completed at journal 29 Apr, 2026 First submitted to journal 27 Apr, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9542115","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":634023979,"identity":"af9606a9-3fa7-43e7-bfd4-30bc361f2fdd","order_by":0,"name":"Thomas Maudhuizon","email":"data:image/png;base64,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","orcid":"","institution":"Centre Hospitalier Universitaire de Rouen","correspondingAuthor":true,"prefix":"","firstName":"Thomas","middleName":"","lastName":"Maudhuizon","suffix":""},{"id":634023980,"identity":"033cde4f-0bba-47b3-94c9-f81d43ea7cfe","order_by":1,"name":"Zoé Demailly","email":"","orcid":"","institution":"Centre Hospitalier Universitaire de Rouen","correspondingAuthor":false,"prefix":"","firstName":"Zoé","middleName":"","lastName":"Demailly","suffix":""},{"id":634023981,"identity":"2187555f-2577-452c-983d-6377bf94dc1c","order_by":2,"name":"Charles Fauvel","email":"","orcid":"","institution":"Centre Hospitalier Universitaire de Rouen","correspondingAuthor":false,"prefix":"","firstName":"Charles","middleName":"","lastName":"Fauvel","suffix":""},{"id":634023982,"identity":"e32c8a90-2bd3-4bde-af1b-834488982a75","order_by":3,"name":"Fabienne Tamion","email":"","orcid":"","institution":"Centre Hospitalier Universitaire de Rouen","correspondingAuthor":false,"prefix":"","firstName":"Fabienne","middleName":"","lastName":"Tamion","suffix":""},{"id":634023983,"identity":"354876d1-765c-4d4e-ac06-8be8d9cdb368","order_by":4,"name":"Dominique Vodovar","email":"","orcid":"","institution":"Centre Hospitalier Universitaire de Rouen","correspondingAuthor":false,"prefix":"","firstName":"Dominique","middleName":"","lastName":"Vodovar","suffix":""},{"id":634023984,"identity":"2f526229-32a6-46bf-a31c-8be9f0f1651f","order_by":5,"name":"Jonathan Nicolas","email":"","orcid":"","institution":"Centre Hospitalier Universitaire de Rouen","correspondingAuthor":false,"prefix":"","firstName":"Jonathan","middleName":"","lastName":"Nicolas","suffix":""}],"badges":[],"createdAt":"2026-04-27 12:57:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9542115/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9542115/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":109012170,"identity":"f75b67cd-5e26-4f03-b271-92b194393d1b","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":113017,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEchocardiographic assessment of the subcostal right ventricular outflow tract (RVOT\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSC\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e).\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA: Pulsed-wave Doppler in the RVOT\u003csub\u003eSC\u003c/sub\u003e, with the angled cursor indicating the sampling site. B: Measurement of RVOT\u003csub\u003eSC\u003c/sub\u003e velocity–time integral (VTI). C: Measurement of RVOT\u003csub\u003eSC\u003c/sub\u003e diameter (RVOT\u003csub\u003eSC\u003c/sub\u003ed).\u003c/p\u003e\n\u003cp\u003e(Personal images.)\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/d569a2806900f042df2180e0.jpg"},{"id":109012171,"identity":"a17dbd98-886f-4253-9c8d-cc5ba4ff1414","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":87767,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEchocardiographic protocol. \u003c/strong\u003eA baseline examination was performed to estimate cardiac output using both CO\u003csub\u003eSC\u003c/sub\u003e and CO\u003csub\u003eSTD\u003c/sub\u003e, based on RVOT\u003csub\u003eSC\u003c/sub\u003e VTI, RVOT\u003csub\u003eSC\u003c/sub\u003ed, LVOT VTI, and LVOTd at the initial position (t0). At 30–60 seconds after passive leg raising (t1\u003csub\u003ePLR\u003c/sub\u003e) and after returning to baseline (t2), only RVOT\u003csub\u003eSC\u003c/sub\u003e VTI and LVOT VTI were reassessed.\u003c/p\u003e\n\u003cp\u003e(Baseline echographic parameters included: left ventricular ejection fraction (visually in 10% increments), mitral E/A ratio, mitral E/e’ ratio, mitral E-wave deceleration time (ms), mitral tissue doppler S’ velocity (m/s), diastolic interventricular septum thickness (mm), tricuspid S’ velocity (m/s), tricuspid annular plane systolic excursion (mm), tricuspid regurgitation peak velocity (m/s), RV/LV diameter ratio, pulmonary acceleration time (ms), right atrial area (cm²), biplane left atrial volume index (mL/m²), inferior vena cava diameter (mm) and its respiratory variation (%) and estimated systolic pulmonary artery pressure (mmHg), A – mitral A wave, E– mitral E wave, e’ – lateral e’ mitral tissular velocity, CO\u003csub\u003eSC\u003c/sub\u003e – Subcostal cardiac output, CO\u003csub\u003eSTD\u003c/sub\u003e – standard cardiac output, LV – Left ventricle, LVOTd – left ventricle outflow tract diameter, LVOT VTI – left ventricle outflow tract velocity time integral, RV – Right ventricle, RVOT\u003csub\u003eSC\u003c/sub\u003ed – right ventricle outflow tract diameter, RVOT\u003csub\u003eSC'\u003c/sub\u003e VTI – right ventricle outflow tract velocity time integral.)\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/ae40d11c993d3d47c37cc373.jpg"},{"id":109012179,"identity":"fc9cbc5d-d754-48ff-afa6-116d7597b0be","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":83248,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFlowchart of the study.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(CO: Cardiac output; ICU: Intensive Care Unit; VTI: velocity time integral)\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/3606a9651ee5c15e6e073c1c.jpg"},{"id":109012173,"identity":"147ecc42-fb42-43f1-b8e0-2a58759abf98","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":67775,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA: Scatter plots of paired CO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSC\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e and CO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSTD\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e (L/min) measurements at t0, t1\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003ePLR\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e, and t2. B: Scatter plots of paired RVOT\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSC\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e VTI and LVOT VTI (cm) measurements at t0, t1\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003ePLR\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e, and t2.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(CO\u003csub\u003eSC\u003c/sub\u003e: subcostal cardiac output; CO\u003csub\u003eSTD\u003c/sub\u003e: standard cardiac output; LVOT VTI: left ventricular outflow tract velocity-time integral; RVOT\u003csub\u003eSC\u003c/sub\u003e VTI: subcostal right ventricular outflow tract velocity-time integral; PLR: passive leg raising; t0: baseline measurement before PLR; t1\u003csub\u003ePLR\u003c/sub\u003e: measurement 30-60 seconds after PLR; t2: measurement 60 seconds after returning to baseline.)\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/0bf17094db019ae545c13dba.jpg"},{"id":109012183,"identity":"818b8be2-e111-4d71-a050-01163ee3cf71","added_by":"auto","created_at":"2026-05-11 16:51:05","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":68676,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScatter plot of paired ΔLVOT VTI and ΔRVOT\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSC\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e VTI following a PLR\u0026nbsp; maneuver.\u003c/strong\u003e Colored lines indicate thresholds for preload responsiveness: blue, x = 15.9%; green, x = 13.04%; red, y = 12%. The dashed grey line x=12.1% represent the optimal cutoff ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI to detect ΔLVOT VTI \u0026gt; 12% following a PLR, based on the Youden Index\u003cem\u003e.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e(ΔLVOT VTI – variation of left ventricular outflow tract velocity time integral, ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI – variation of subcostal right ventricular outflow tract velocity time integral\u003cbr\u003e\n, ICC – Intraclass coefficient index, PLR – passive leg raising).\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/48d62a94671da5da46bf38e5.jpg"},{"id":109068148,"identity":"417fbb77-f579-48d1-9c89-4b4fc15416c6","added_by":"auto","created_at":"2026-05-12 10:04:03","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":942099,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/7bb5cd84-3718-4599-9af2-e801306910e4.pdf"},{"id":109012172,"identity":"bcd2a642-971b-412e-9047-092065968a0f","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":121329,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAdditional file 1: Feasibility (%) of obtaining the required echocardiographic windows (n = 72).\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(A5C – Apical 5-chamber window, PLAX – Parasternal long-axis window, SC – subcostal window, t0 – baseline measurement before PLR, t1\u003csub\u003ePLR\u003c/sub\u003e – measurement 30 to 60 seconds after passive leg raising, t2 – measurement 60 seconds after returning to baseline.)\u003c/p\u003e","description":"","filename":"AdditionalFile1.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/fa805a84c75be15ac07accda.pdf"},{"id":109012178,"identity":"bac51ea3-6b14-4840-b6eb-f232242bec83","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"pdf","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":61746,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAdditional file 2: Failure rates (%) for cardiac output-related echocardiographic parameters (n = 72).\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(CO\u003csub\u003eSC\u003c/sub\u003e – Subcostal cardiac output, CO\u003csub\u003eSTD\u003c/sub\u003e Standard cardiac output, LVOT VTI – Left ventricular outflow tract velocity time integral, RVOT\u003csub\u003eSC\u003c/sub\u003e VTI – Subcostal right ventricular outflow tract velocity time integral, t0 – baseline measurement before PLR, t1\u003csub\u003ePLR\u003c/sub\u003e – measurement 30 to 60 seconds after passive leg raising, t2 – measurement 60 seconds after returning to baseline.)\u003c/p\u003e","description":"","filename":"AdditionalFile2.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/fa4ed5a46dc56849421b8fa1.pdf"},{"id":109012182,"identity":"6be13b89-7086-4192-b226-bf20dd2a4c7f","added_by":"auto","created_at":"2026-05-11 16:51:05","extension":"pdf","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":185735,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAdditional file 3: Patient characteristics and clinical status at complete echocardiographic examination\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(ARDS – Acute respiratory distress syndrome, BMI – Body Mass Index, FiO\u003csub\u003e2\u003c/sub\u003e – Fraction of inspired oxygen, IQR – Interquartile range, NIV – Non-invasive ventilation, PEEP – Positive end-expiratory pressure, SAPS II – Simplified Acute Physiology Score II.)\u003c/p\u003e","description":"","filename":"AdditionalFile3.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/88c5669d9c7b9b2e5b1d8960.pdf"},{"id":109012176,"identity":"1c279ed0-677f-43c6-abf8-2a27d554e523","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"pdf","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":50187,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAdditional file 4: A: Scatter plots representing paired CO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSC\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e and CO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSTD\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e at t0, t1\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003ePLR\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e, and t2. B: Scatter plots representing paired RVOT\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSC\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e VTI and LVOT VTI at t0, t1\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003ePLR\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e, and t2.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEach color corresponds to a different patient, and dashed arrows indicate the trajectory of CO and VTI variations over time (from t0 to t1\u003csub\u003ePLR\u003c/sub\u003e, and from t1\u003csub\u003ePLR\u003c/sub\u003e to t2).\u003c/p\u003e\n\u003cp\u003e(CO\u003csub\u003eSC\u003c/sub\u003e – Subcostal cardiac output, CO\u003csub\u003eSTD\u003c/sub\u003e – Standard cardiac output, LVOT VTI – Left ventricular outflow tract velocity time integral, PLR – passive leg raising, RVOT\u003csub\u003eSC\u003c/sub\u003e VTI – Subcostal right ventricular outflow tract velocity time integral, t0 – baseline measurement before PLR, t1\u003csub\u003ePLR\u003c/sub\u003e – measurement 30 to 60 seconds after passive leg raisig, t2 – measurement 60 seconds after returning to baseline.)\u003c/p\u003e","description":"","filename":"AdditionalFile4.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/9da81de6b2b1660aac545015.pdf"},{"id":109012180,"identity":"10077e4c-45b3-46a6-9f4d-83b70ffb376c","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"pdf","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":34225,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAdditional file 5: Bland-Altman plot between CO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSC\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e and CO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSTD\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e (L/min).\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(CO\u003csub\u003eSC\u003c/sub\u003e – Subcostal cardiac output, CO\u003csub\u003eSTD\u003c/sub\u003e – Standard cardiac output, SD – Standard deviation.)\u003c/p\u003e","description":"","filename":"AdditionalFile5.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/02d10e25d8de976cb8bd8f75.pdf"},{"id":109012174,"identity":"61a2bd89-6967-4ec2-ac4d-e93b18204342","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"pdf","order_by":6,"title":"","display":"","copyAsset":false,"role":"supplement","size":120502,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAdditional file 6: Contingency table of diagnostic performance of ΔRVOTSC VTI \u0026gt;15.9% to detect ΔLVOT VTI ≥ 12% following a PLR (n = 50)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(ΔLVOT VTI – variation of left ventricular outflow tract velocity time integral, ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI variation of subcostal right ventricular outflow tract velocity time integral, PLR – Passive leg raising).\u003c/p\u003e","description":"","filename":"AdditionalFile6.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/c9427267a09b14f5514275b6.pdf"},{"id":109012177,"identity":"a897febb-14c8-44ea-b5c3-492b0dedf90d","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"pdf","order_by":7,"title":"","display":"","copyAsset":false,"role":"supplement","size":120660,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAdditional file 7: Contingency table of diagnostic performance of ΔRVOT\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSC\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e VTI ≥ 13.04% to detect ΔLVOT VTI ≥ 12% following a PLR (n = 50)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(ΔLVOT VTI – variation of left ventricular outflow tract velocity time integral, ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI variation of subcostal right ventricular outflow tract velocity time integral, PLR – Passive leg raising).\u003c/p\u003e","description":"","filename":"AdditionalFile7.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/f6054d3b4c30e0ccc1382bc1.pdf"},{"id":109012181,"identity":"709bc27d-d228-42bd-a2ac-0f82e22d6e04","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"pdf","order_by":8,"title":"","display":"","copyAsset":false,"role":"supplement","size":27582,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAdditional file 8: ROC curves for ΔRVOT\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSC\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e VTI to detect ΔLVOT VTI following a PLR.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(AUC – Area under the curve, ROC – Receiver operating characteristic, ΔLVOT VTI – Variation of left ventricular outflow tract velocity time integral, ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI – Variation of subcostal right ventricular outflow tract velocity time integral, PLR – Passive leg raising).\u003c/p\u003e","description":"","filename":"AdditionalFile8.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/c460c745f316b1d5b1639707.pdf"},{"id":109012175,"identity":"4918a8be-4f8a-4d2c-8ffc-a5931c90de3a","added_by":"auto","created_at":"2026-05-11 16:51:04","extension":"pdf","order_by":9,"title":"","display":"","copyAsset":false,"role":"supplement","size":124468,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAdditional file 9: Contingency table of diagnostic performance of ΔRVOT\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eSC\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e VTI \u0026gt; 12.01% to detect ΔLVOT VTI ≥ 12% following a PLR (n = 50)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(ΔLVOT VTI – variation of left ventricular outflow tract velocity time integral, ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI variation of subcostal right ventricular outflow tract velocity time integral, PLR – Passive leg raising).\u003c/p\u003e","description":"","filename":"AdditionalFile9.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9542115/v1/21e249eaae2768ca763ee182.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Prospective evaluation of a subcostal echocardiographic cardiac output measurement in critically ill patients compared with standard transthoracic echocardiography measurement – The Right Way","fulltext":[{"header":"Introduction","content":"\u003cp\u003eHemodynamic monitoring of cardiac output (CO) is essential for diagnosing shock, identifying its underlying mechanisms and guiding therapy [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Traditionally measured using a pulmonary artery catheter, CO can nowadays be assessed invasively via transpulmonary thermodilution with pulse contour analysis or noninvasively using transthoracic echocardiography (TTE) [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Over the past decade, TTE has become widely available in critical care, providing a reliable, rapid and dynamic tool for CO measurement and cardiovascular assessment across a wide range of clinical conditions and beyond shock [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eUsing TTE, standard cardiac output (CO\u003csub\u003eSTD\u003c/sub\u003e ) is assessed by measuring both the left ventricular outflow tract diameter (LVOTd) allowing to calculate the LVOT area, obtained from the parasternal long-axis (PLAX) view and the left ventricular outflow tract velocity-time integral (LVOT VTI), obtained from the apical five-chamber (A5C) window [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Multiplying the LVOT area by the LVOT VTI yields the stroke volume (SV) which, when multiplied by heart rate (HR), provides the CO\u003csub\u003eSTD\u003c/sub\u003e. However, acquisition of these echocardiographic parameters can be technically challenging in the intensive care unit (ICU) due to critical illness, invasive mechanical ventilation and positioning limitations [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn this context, the subcostal (SC) echocardiographic window is often preferred in emergency settings [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], but does not allow reliable assessment of CO. In contrast, the subcostal parasternal short-axis (PSAX\u003csub\u003eSC\u003c/sub\u003e) view of the right ventricular outflow tract (RVOT\u003csub\u003eSC\u003c/sub\u003e) allows measurement of both the subcostal right ventricular outflow tract diameter (RVOT\u003csub\u003eSC\u003c/sub\u003ed) and the velocity\u0026ndash;time integral (RVOT\u003csub\u003eSC\u003c/sub\u003e VTI) [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Since systemic and pulmonary CO are generally considered equivalent, except possibly in moribund patients, subcostal cardiac output (CO\u003csub\u003eSC\u003c/sub\u003e) assessment could serve as a reliable surrogate for CO\u003csub\u003eSTD\u003c/sub\u003e. This approach is a promising alternative for CO estimation, with a retrospective study of 30 patients showing good correlation between LVOT VTI and RVOT\u003csub\u003eSC\u003c/sub\u003e VTI [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFurthermore, in the ICU, passive leg raising (PLR) manoeuvre is commonly used to guide fluid resuscitation [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. A change in LVOT VTI (ΔLVOT VTI)\u0026thinsp;\u0026ge;\u0026thinsp;12% following PLR manoeuvre is well established as a predictor of fluid responsiveness [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Given that RVOT\u003csub\u003eSC\u003c/sub\u003ed is not expected to change with PLR \u0026ndash; similarly to LVOTd \u0026ndash; reliable RVOT\u003csub\u003eSC\u003c/sub\u003e VTI measurement could serve as an alternative tool to guide fluid management. Recently two prospective studies demonstrated that a change in RVOT\u003csub\u003eSC\u003c/sub\u003e VTI (ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI)\u0026thinsp;\u0026gt;\u0026thinsp;15.9% or \u0026ge;\u0026thinsp;13.04% following PLR manoeuvre could identified preload-responsiveness [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThis prospective study aimed to evaluate the agreement between CO\u003csub\u003eSTD\u003c/sub\u003e and CO\u003csub\u003eSC\u003c/sub\u003e measurements which has not previously been assessed. The study also focused on the ability of ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI to detect preload-responsiveness.\u003c/p\u003e"},{"header":"Patients and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design and setting\u003c/h2\u003e \u003cp\u003eThis was a single-center prospective observational study carried out from November 2024 to July 2025 in the medical ICU of Charles Nicolle University Hospital, Rouen, France. The study protocol was registered (NCT07177391) and approved by the Ile de France VII Ethics Committee (2024-A01706-41). The study adhered to the European Society of Intensive Care Medicine (ESICM) recommendations for clinical echocardiography research (PRICES) [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Informed non-opposition was obtained via written information sheets provided to patients, legal representatives or families.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eStudy Objectives\u003c/h3\u003e\n\u003cp\u003eThe primary objective was to assess the agreement between CO\u003csub\u003eSC\u003c/sub\u003e and CO\u003csub\u003eSTD\u003c/sub\u003e. Secondary objectives included: 1) determining the mean bias and limits of agreement between CO\u003csub\u003eSC\u003c/sub\u003e and CO\u003csub\u003eSTD\u003c/sub\u003e; 2) assessing the feasibility of acoustic window acquisitions, defined as the ability to obtain the predefined echocardiographic windows required for CO measurement in all patients; 3) determining the failure rate of CO measurement, defined as the inability to complete these measurements regardless of initial feasibility status; 4) evaluating the correlation between LVOT VTI and RVOT\u003csub\u003eSC\u003c/sub\u003e VTI and 5) evaluating the diagnostic performance of ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI following PLR manoeuvre for detecting\u0026thinsp;\u0026ge;\u0026thinsp;12% ΔLVOT VTI.\u003c/p\u003e\n\u003ch3\u003eParticipants\u003c/h3\u003e\n\u003cp\u003eAdult patients (\u0026ge;\u0026thinsp;18 years) admitted to the ICU were screened for inclusion whenever a TTE was clinically indicated for circulatory failure, dyspnea, hemodynamic monitoring, therapeutic follow-up, volume status assessment, or suspicion of infective endocarditis. Enrolment was non-consecutive, depending on investigator and equipment availability, and a single patient could undergo repeated assessments based on clinical requirements. Patients or their legal representatives who retrospectively opposed data storage or research use were not enrolled. Patients with grade\u0026thinsp;\u0026ge;\u0026thinsp;3 aortic or pulmonary regurgitation, those unable to undergo the PLR manoeuvre, patients with intracranial hypertension or intra-abdominal hypertension, individuals under legal protection or deprived of liberty, pregnant patients and moribund patients were also excluded.\u003c/p\u003e\n\u003ch3\u003eProtocol\u003c/h3\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eEchocardiographic measurements\u003c/h2\u003e \u003cp\u003eEchocardiography was performed using a Vivid S70 (General Electric, Milwaukee, WI, USA) equipped with a 3-MHz 12S-RS cardiac transducer. Following completion of the examination, images and cine loops were exported for analysis. Echocardiographic examinations were performed by a single senior intensivist certified in critical care echocardiography.\u003c/p\u003e \u003cp\u003eStandard echocardiographic measurements were performed on parasternal short-axis (PSAX), PLAX, apical 3-chamber, apical 4-chamber, A5C and SC following current guidelines [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. According to the guidelines, three measurements were performed for all patients and five in case of atrial fibrillation (AF) [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Valvular diseases were screened and in cases where severe aortic or pulmonary regurgitation was identified or suspected by the investigator, final confirmation was performed through cardiologic assessment. HR was calculated from echocardiographic RR intervals and averaged to the nearest integer. RVOT\u003csub\u003eSC\u003c/sub\u003e VTI and RVOT\u003csub\u003eSC\u003c/sub\u003ed were obtained in the same SC view, angled to capture the RVOT and pulmonary artery \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Measurement quality criteria were extrapolated from LV and RV recommendations [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. When applicable, multiple TTE examinations per patient were sequentially numbered.\u003c/p\u003e \u003cp\u003eCO was calculated using HR, SV, ventricular outflow tract diameter (VOTd), and velocity-time integral (VTI) as follow:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:CO=\\:HR\\times\\:SV=\\:HR\\times\\:VTI\\times\\:\\pi\\:\\times\\:{\\left(\\frac{VOTd}{2}\\right)}^{2}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003ePassive leg raising and complete examination\u003c/h2\u003e \u003cp\u003eA complete echocardiographic examination consisted of a baseline assessment which served as the reference procedure [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Then, two consecutive PLR manoeuvres were performed according to guidelines [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], separated by 2 minutes: the first for CO\u003csub\u003eSTD\u003c/sub\u003e and the second for CO\u003csub\u003eSC\u003c/sub\u003e\u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. For each manoeuvre, parameters were assessed before PLR (t0), at 30 to 60 seconds after PLR (t1\u003csub\u003ePLR\u003c/sub\u003e) and at 1 minute after returning to the baseline position (t2).\u003c/p\u003e \u003cp\u003eA positive PLR response for LVOT VTI was defined as a ΔLVOT VTI\u0026thinsp;\u0026ge;\u0026thinsp;12% based on the least significant change of 12% calculated for a single operator, ensuring the value exceeded measurement noise in the ICU setting [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] and aligned with established echocardiographic PLR CO variation thresholds [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Regarding ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI, a higher positivity thresholds of \u0026gt;\u0026thinsp;15.9% and \u0026ge;\u0026thinsp;13.04 were also considered in accordance with previous literature [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Reversibility was assessed by comparing variation in HR and VTI between t0 and t2. Identical thresholds were applied to both intubated and spontaneously breathing patients. All PLR manoeuvres were performed without repositioning the echocardiographic probe or altering catecholamine dosages and ventilator settings [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eData collection\u003c/h3\u003e\n\u003cp\u003eIn addition to echocardiographic data, clinical data were collected prospectively, including diagnostic parameters, vital signs, relevant medical history, therapies, the Simplified Acute Physiology Score II score [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], and the Sequential Organ Failure Assessment (SOFA) score [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eCategorical variables were reported as numbers (percentages) and compared using the chi-square test. Continuous variables were reported as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation or median (interquartile range), as appropriate. Distribution of continuous variables was assessed graphically to limit the multiplicity of formal statistical tests, with the Shapiro-Wilk test applied when non-normality was suspected. Variables were compared using the Student\u0026rsquo;s t-test or the Mann\u0026ndash;Whitney U test, as appropriate. Differences between paired measurements were assessed using the paired Student\u0026rsquo;s t-test for normally distributed data and the Wilcoxon signed-rank test for non-normally distributed data.\u003c/p\u003e \u003cp\u003eAgreement between paired echocardiographic parameters measurement was assessed using intraclass correlation coefficient (ICC) with 95% confidence interval (95% CI). Additional analyses included correlations using Pearson or Spearman analysis as appropriate (r with 95% CI) and assessment of mean bias (\u0026plusmn;\u0026thinsp;limits of agreement) using Bland-Altman plot. The evaluation of the diagnostic performance of ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI following a PLR for detecting a\u0026thinsp;\u0026ge;\u0026thinsp;12% ΔLVOT VTI was assessed using Receiver Operating Characteristic (ROC) curves, with calculation of sensitivity, specificity, positive and negative predictive values, likelihood ratios, and area under the curve (AUC) with 95% CI.\u003c/p\u003e \u003cp\u003eThe number of echocardiographic examinations was calculated based on the primary objective, assuming an ICC, single-measure, absolute agreement of 0.90, an alpha risk of 5%, and with 50 complete examinations (t0, t1\u003csub\u003ePLR\u003c/sub\u003e, t2\u0026ndash;150 measurements) a resulting power of 93%. Only complete examinations were analyzed for primary objective and the diagnostic performance of ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI following a PLR for detecting a\u0026thinsp;\u0026ge;\u0026thinsp;12% ΔLVOT VTI.\u003c/p\u003e \u003cp\u003eAll statistical analyses were performed independently by a statistician, using R software (R Foundation for Statistical Computing, Vienna, Austria). A p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eBetween November 15, 2024, and July 16, 2025, a total of 849 patients were admitted. Among them, 65 critically ill patients were included, representing 74 echocardiographic examinations. Two patients were excluded due to severe aortic and pulmonary regurgitation (grades 3 and 4, respectively).\u003c/p\u003e\n\u003cp\u003eFeasibility of acoustic window acquisitions and failure rate for cardiac output measurements\u003c/p\u003e\n\u003cp\u003eOf the 63 remaining patients, 72 echocardiographic examinations were performed.\u0026nbsp;Feasibility of window acquisition was 79.2% for the SC and 84.7% for the A5C+PLAX combination, with no significant difference: -5.6% (95% CI -17.0% to 5.9%; p = 0.48). Details for each time point are summarized in \u003cstrong\u003eAdditional file 1\u003c/strong\u003e. The overall failure rate for CO measurement was significantly higher for the SC approach compared to the standard method, with 23.1% vs. 13.9% with a difference of 9.2% (95% CI 5.4 to 13.1; p = 0.01). RVOT\u003csub\u003eSC\u003c/sub\u003e VTI and LVOT VTI did not differ significantly in failure rate (26.4% \u003cem\u003eversus\u003c/em\u003e 15.3%; difference 11.1%, 95% CI: -0.2 to 18.6; p = 0.10\u003cstrong\u003e\u0026nbsp;(Table 1, Additional file 2)\u003c/strong\u003e. RVOT\u003csub\u003eSC\u003c/sub\u003ed acquisition failed significantly more often than LVOTd (25.0% \u003cem\u003eversus\u003c/em\u003e 8.3%; difference 16.7%, 95% CI: 5.1-28.2; p = 0.01).\u003c/p\u003e\n\u003cp\u003eOf the 72 echocardiographic examinations performed, 22 were excluded\u0026nbsp;for incomplete data: 21 lacked paired CO measurements and 1 provided only t0 data. This resulted in 50 complete examinations for final analysis, totaling 150 paired CO/VTI measurements \u003cstrong\u003e(Figure 3)\u003c/strong\u003e. The mean number of examinations per patient was 1.11 \u0026plusmn; 0.36.\u003c/p\u003e\n\u003cp\u003eStudy population\u003c/p\u003e\n\u003cp\u003eThe 41 included patients (Additional file 3) were predominantly male (sex ratio 2.4), with a median age of 62\u0026nbsp;(50-69) years and a median body mass index of 23.7 (20.8-26.5) kg/m\u003csup\u003e\u0026sup2;\u003c/sup\u003e. The mean SAPS II score was 46 \u0026plusmn; 2. Shock occurred in 53.7% of patients, 64.1% were mechanically ventilated, and AF was observed in 12.0% of patients. The main echocardiographic characteristics are summarized in Table 2.Agreement of cardiac output measurement\u003c/p\u003e\n\u003cp\u003eThe ICC between CO\u003csub\u003eSC\u0026nbsp;\u003c/sub\u003eand CO\u003csub\u003eSTD\u003c/sub\u003e was excellent with an ICC of 0.91 (95% CI 0.82 to 0.96; p\u0026lt;0.0001) \u003cstrong\u003e(Figure 4A, Additional file 4A)\u0026nbsp;\u003c/strong\u003eand the mean bias (\u0026plusmn; limit of agreement) in CO measurement was -0.06 L/min (-1.27 to 1.15) \u003cstrong\u003e(Additional file 5)\u003c/strong\u003e. RVOT\u003csub\u003eSC\u003c/sub\u003e VTI and LVOT VTI were strongly correlated (r = 0.89; 95% CI: 0.78\u0026ndash;0.93; p \u0026lt; 0.0001) \u003cstrong\u003e(Figure 4B, Additional file 4B)\u003c/strong\u003e. All individual and overall measurements for RVOT\u003csub\u003eSC\u003c/sub\u003e VTI, LVOT VTI, CO\u003csub\u003eSC\u003c/sub\u003e, CO\u003csub\u003eSTD\u003c/sub\u003e, subcostal stroke volume (SV\u003csub\u003eSC\u003c/sub\u003e), standard stroke volume (SV\u003csub\u003eSTD\u003c/sub\u003e), and HR are presented in \u003cstrong\u003eTable 3\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003eAnalysis of preload-responsiveness in the complete records\u003c/p\u003e\n\u003cp\u003eThe ICC for \u0026Delta;VTI following a PLR was good with an ICC of 0.86 (95% CI 0.76 to 0.92; p \u0026lt; 0.0001)\u003cstrong\u003e\u0026nbsp;(Figure 5)\u003c/strong\u003e. HR changes after PLR were minimal and non-significant: 0 bpm (95% CI: -1 to 1; p = 0.64) right-sided, -1 bpm (95% CI: -2 to 0; p = 0.14) left-sided, and 1 bpm (95% CI: -3 to 0; p = 0.12) globally. VTI changes between t0 and t2 were also non significant (LVOT VTI -0.6%, 95% CI: -2.0 to 0.7; p = 0.35; RVOT\u003csub\u003eSC\u003c/sub\u003e VTI -0.7%, 95% CI: -2.1 to 0.6; p = 0.27).\u003c/p\u003e\n\u003cp\u003eUsing a \u0026Delta;RVOTSC VTI \u0026gt;15.9% threshold, 6 true positives and 7 false negatives were identified among responders, with 36 true negatives and 1 false positive among non-responders. With a \u0026ge; 13.04% threshold, 12 true positives and 1 false negative were detected in responders, with 36 true negatives and 1 false positive in non-responders.\u003cstrong\u003e\u0026nbsp;(Additional file 6\u0026ndash;7\u003c/strong\u003e\u003cstrong\u003e)\u003c/strong\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe AUC for \u0026Delta;RVOT\u003csub\u003eSC\u003c/sub\u003e VTI to detected \u0026Delta;LVOT VTI was 0.98 (95% CI 0.95 to 1.00) \u003cstrong\u003e(Additional file 8)\u003c/strong\u003e. A \u0026Delta;RVOT\u003csub\u003eSC\u003c/sub\u003e VTI \u0026gt; 15.9% detected a \u0026Delta;LVOT VTI \u0026ge; 12% following a PLR with a sensitivity of 46.2% (95% CI 19.2 to 74.9), a specificity of 97.3% (95% CI 85.8 to 99.9), a positive predictive value 85.7% (95% CI 42.1 to 99.6), a negative predictive value 83.7% (95% CI 69.3 to 93.2), a positive likelihood ratio of 17.1 (95% CI 2.3 to 128.8), a negative likelihood ratio of 0.6 (95% CI 0.3 to 0.9). A \u0026Delta;RVOT\u003csub\u003eSC\u003c/sub\u003e VTI \u0026ge; 13.04% yielded a sensitivity of 92.3% (95% CI 64.0 to 99.8), a specificity of 97.3% (95% CI 85.8 to 99.9), a positive predictive value of 92.3% (95% CI 64.0 to 99.8), a negative predictive value of 97.3% (95% CI 85.8 to 99.9), a positive likelihood ratio of 34.2 (95% CI 4.91 to 237.6), a negative likelihood ratio of 0.079 (95% CI 0.012 to 0.520), and an AUC of 0.98 (95% CI 0.95 to 1.00).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe optimal \u0026Delta;RVOT\u003csub\u003eSC\u003c/sub\u003e VTI threshold determined by the Youden index (\u003cem\u003eJ\u003c/em\u003e = 0.90, 95% CI 0.72 to 1.00) was 12.1%, which demonstrated identical diagnostic performance to the \u0026ge; 13.04% threshold \u003cstrong\u003e(Additional file 9)\u003c/strong\u003e.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this exploratory study of applied bedside hemodynamic physiology, CO\u003csub\u003eSC\u003c/sub\u003e and CO\u003csub\u003eSTD\u003c/sub\u003e demonstrated excellent agreement, supported by a little mean bias between both of the measurement and a strong correlation between RVOT\u003csub\u003eSC\u003c/sub\u003e and LVOT VTI. High reliability was also observed for ΔVTI measurements following a PLR maneuver. We also identified an optimal threshold of \u0026gt;\u0026thinsp;12.1% for predicting fluid responsiveness based on ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI. The feasibility of SC acoustic window acquisition was similar to that of the standard A5C\u0026thinsp;+\u0026thinsp;PLAX views, but the overall failure rate for CO\u003csub\u003eSC\u003c/sub\u003e measurement was higher, due to a lower rate of successful RVOT\u003csub\u003eSC\u003c/sub\u003ed acquisition.\u003c/p\u003e \u003cp\u003eA previous study reported a mean difference of \u0026minus;\u0026thinsp;5.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8 cm between LVOT VTI and RVOT\u003csub\u003eSC\u003c/sub\u003e VTI (ICC 0.73; 95% CI: 0.62\u0026ndash;0.81) [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Extending these findings, our study is the first to directly assess agreement between CO\u003csub\u003eSC\u003c/sub\u003e and CO\u003csub\u003eSTD\u003c/sub\u003e. Although RVOT\u003csub\u003eSC\u003c/sub\u003e VTI was significantly lower than LVOT VTI, this was offset by a larger RVOT\u003csub\u003eSC\u003c/sub\u003e diameter resulting in preserved equivalence between CO\u003csub\u003eSC\u003c/sub\u003e and CO\u003csub\u003eSTD\u003c/sub\u003e. Despite the lack of established reference values for RVOT\u003csub\u003eSC\u003c/sub\u003e measurements, our results are consistent with standard RVOT estimates and international echocardiography guidelines [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThese findings are physiologically coherent: while the subcostal view does not permit reliable LVOT assessment because of poor alignment [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], it provides an optimal axis for the RVOT [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Prior studies have confirmed the feasibility of RVOT\u003csub\u003eSC\u003c/sub\u003e VTI acquisition, showing subcostal pulmonary acceleration time comparable to that obtained in the standard PSAX view [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In our cohort, excellent agreement was demonstrated between CO measurements despite respiratory-induced artifacts and pulmonary transit delays [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], suggesting that rigorous VTI averaging effectively neutralizes these cyclical variations.\u003c/p\u003e \u003cp\u003eThe SC view demonstrated similar feasibility of acoustic window acquisition compared with the standard A5C\u0026thinsp;+\u0026thinsp;PLAX views, but a lower overall success rate for cardiac output measurement. However, 6.9% of examinations relied exclusively on the SC view because PLAX and/or A5C windows were unobtainable. In settings in which TTE is essential for rapid hemodynamic assessment in shock [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], this finding is clinically relevant. Given the demonstrated reliability of CO\u003csub\u003eSC\u003c/sub\u003e and RVOT\u003csub\u003eSC\u003c/sub\u003e VTI, the SC approach represents a pragmatic alternative when standard views are not accessible, potentially limiting the need for transesophageal echocardiography or invasive monitoring unless otherwise clinically indicated [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Another key advantage of this method is that it requires only a single echocardiographic window. Unlike CO\u003csub\u003eSTD\u003c/sub\u003e, which combines PLAX and A5C views and may increase measurement error and failure in the ICU, the SC window is widely recognized for its accessibility [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], even during mechanical ventilation [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Given the excellent agreement observed in our heterogeneous ICU cohort \u0026ndash; most of whom were intubated and receiving catecholamines \u0026ndash; CO\u003csub\u003eSC\u003c/sub\u003e represents a promising tool for rapid hemodynamic assessment in emergency settings.\u003c/p\u003e \u003cp\u003eIn our cohort, a ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI threshold of 12.1% for predicting fluid responsiveness demonstrated excellent diagnostic performance. Preload responsiveness was assessed with good correlation between RVOT\u003csub\u003eSC\u003c/sub\u003e VTI and LVOT VTI measurements across all time points, and importantly, the reversibility of the PLR effect was consistently demonstrated. While ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI following a PLR have been reported previously [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], no consensus threshold has been established. The tested threshold is highly consistent with the recently proposed\u0026thinsp;\u0026ge;\u0026thinsp;13.04% cutoff [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], which, when applied to our population, yielded comparable diagnostic performance. By contrast, the \u0026gt;\u0026thinsp;15.9% threshold [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] showed high specificity but poor sensitivity, likely reflecting methodological differences, as the reference study employed manual leg raising ; a technique now discouraged due to potential sympathetic stimulation and HR-mediated increases in CO [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Importantly, our 12.1% threshold closely approximates the standard ΔLVOT VTI\u0026thinsp;\u0026ge;\u0026thinsp;12% criterion for fluid responsiveness. Although this requires prospective validation, theoretical considerations based on the CO formula and assuming constant LVOT and RVOT diameters suggest that relative VTI variations on the right ventricle should closely parallel those observed on the left.\u003c/p\u003e \u003cp\u003eSeveral limitations warrant consideration. First, its exploratory, single-center, single-operator design precluded the assessment of inter-observer variability, a known source of bias in bedside echocardiography [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Study findings may have also been influenced by the open-label design, the lack of a centralized core lab, and potential selection bias due to operator and equipment availability. Secondly, while CO\u003csub\u003eSTD\u003c/sub\u003e served as reference, invasive gold standards such as pulmonary artery catheterization or transpulmonary thermodilution with pulse contour analysis remain more accurate for CO and preload-responsiveness assessment in the ICU [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Because invasive monitoring was available in only four patients, meaningful comparisons were not feasible. Thirdly, the quality of RVOT\u003csub\u003eSC\u003c/sub\u003ed and RVOT\u003csub\u003eSC\u003c/sub\u003e VTI acquisition remain important considerations. Although acoustic window feasibility was similar between PLAX+A5C and SC views, the higher failure rate of RVOT\u003csub\u003eSC\u003c/sub\u003ed compared to LVOTd measurements resulted in a significantly increased risk of unsuccessful CO\u003csub\u003eSC\u003c/sub\u003e assessment. In practice, prioritizing a reliable RVOT\u003csub\u003eSC\u003c/sub\u003e VTI measurement may be preferable when RVOT\u003csub\u003eSC\u003c/sub\u003ed acquisition is suboptimal; alternative methods should be considered when precise CO monitoring is required. Fourthly, comparing RVOT\u003csub\u003eSC\u003c/sub\u003e VTI and RVOT\u003csub\u003eSC\u003c/sub\u003ed directly with measurements from the PSAX window would have further strengthened the validity of our approach. To date, only one study has explored this, reporting strong ICC [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Finally, fluid administration was not performed after the PLR in preload-responsive patients and only the ability of ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI to predict ΔLVOT VTI was assessed from a physiological perspective [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] and these results must be interpreted in the context of these limitations [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eEchocardiographic CO\u003csub\u003eSC\u003c/sub\u003e measurement is reliable and demonstrates excellent agreement with the standard TTE CO\u003csub\u003eSTD\u003c/sub\u003e. LVOT and RVOT\u003csub\u003eSC\u003c/sub\u003e VTI are highly correlated, further supporting the physiological consistency of right- and left-sided echocardiographic measurements. A ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI threshold of 12.1% after PLR showed excellent diagnostic performance for predicting fluid responsiveness. Future studies are required to confirm the utility of CO\u003csub\u003eSC\u003c/sub\u003e, ideally in comparison with thermodilution-based measurements to strengthen the generalizability of this method. Confirmation of the 12.1% ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI threshold, following PLR, warrants further exploration in larger prospective cohorts.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eA3C\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eApical 3-chamber\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eA4C\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eApical 4-chamber\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eA5C\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eApical 5-chamber\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eAF\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eAtrial fibrillation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eAUC\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eArea under the curve\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eCI\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eConfidence interval\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eCO\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eCardiac output\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eCO\u003c/b\u003e\u003csub\u003e\u003cb\u003eSC\u003c/b\u003e\u003c/sub\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSubcostal cardiac output\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eCO\u003c/b\u003e\u003csub\u003e\u003cb\u003eSTD\u003c/b\u003e\u003c/sub\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eStandard cardiac output\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eESICM\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eEuropean Society of Intensive Care Medicine\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eHR\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eHeart rate\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eICC\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eIntraclass correlation coefficient\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eICU\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eIntensive care unit\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eLV\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eLeft ventricular\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eLVOT\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eLeft ventricular outflow tract\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eLVOTd\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eLeft ventricular outflow tract diameter\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eLVOT VTI\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eLeft ventricular outflow tract velocity-time integral\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003ePLAX\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eParasternal long-axis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003ePLR\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ePassive leg raising\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003ePSAX\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eParasternal short-axis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003ePSAX\u003c/b\u003e\u003csub\u003e\u003cb\u003eSC\u003c/b\u003e\u003c/sub\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSubcostal parasternal short-axis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eROC\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eReceiver Operating Characteristic\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eRV\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eRight ventricular\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eRVOT\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eRight ventricular outflow tract\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eRVOT\u003c/b\u003e\u003csub\u003e\u003cb\u003eSC\u003c/b\u003e\u003c/sub\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSubcostal right ventricular outflow tract\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eRVOT\u003c/b\u003e\u003csub\u003e\u003cb\u003eSC\u003c/b\u003e\u003c/sub\u003e\u003cb\u003ed\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSubcostal right ventricular outflow tract diameter\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eRVOT\u003c/b\u003e\u003csub\u003e\u003cb\u003eSC\u003c/b\u003e\u003c/sub\u003e \u003cb\u003eVTI\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSubcostal right ventricular outflow tract velocity-time integral\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eRVOTd\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eRight ventricular outflow tract diameter\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eSAPS II\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSimplified Acute Physiology Score II\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eSC\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSubcostal\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eSOFA\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSequential Organ Failure Assessment\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eSV\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eStroke volume\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eSV\u003c/b\u003e\u003csub\u003e\u003cb\u003eSC\u003c/b\u003e\u003c/sub\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSubcostal stroke volume\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eSV\u003c/b\u003e\u003csub\u003e\u003cb\u003eSTD\u003c/b\u003e\u003c/sub\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eStandard stroke volume\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eTTE\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eTransthoracic echocardiography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eVOTd\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eVentricular outflow tract diameter\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eVTI\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eVelocity-time integral\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eΔLVOT VTI\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eChange in left ventricular outflow tract velocity-time integral\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eΔRVOT\u003c/b\u003e\u003csub\u003e\u003cb\u003eSC\u003c/b\u003e\u003c/sub\u003e \u003cb\u003eVTI\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eChange in subcostal right ventricular outflow tract velocity-time integral\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e\u003cb\u003eΔVTI\u003c/b\u003e\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eChange in velocity-time integral\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003eEthics approval and consent to participate\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eApproved by the Ile de France VII Ethics Committee (2024-A01706-41). Informed non-opposition was obtained from all participants or their legal representatives.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConsent for publication\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003eAvailability of data and materials\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe datasets used and analyzed during the current study are available from the corresponding author on reasonable request.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCompeting interests\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe authors declare that they have no relevant financial or non-financial interests to disclose.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNone.\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTM designed the study. TM and collected the data. CF, FT, JN and DV provided critical revision of the manuscript. All authors read and approved the final manuscript.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMonnet X, Messina A, Greco M, et al (2025) ESICM guidelines on circulatory shock and hemodynamic monitoring 2025. Intensive Care Med. https://doi.org/10.1007/s00134-025-08137-z\u003c/li\u003e\n\u003cli\u003eMcLean AS (2016) Echocardiography in shock management. Crit Care Lond Engl 20:275. https://doi.org/10.1186/s13054-016-1401-7\u003c/li\u003e\n\u003cli\u003eLevitov A, Frankel HL, Blaivas M, et al (2016) Guidelines for the Appropriate Use of Bedside General and Cardiac Ultrasonography in the Evaluation of Critically Ill Patients\u0026mdash;Part II: Cardiac Ultrasonography. Crit Care Med 44:1206. https://doi.org/10.1097/CCM.0000000000001847\u003c/li\u003e\n\u003cli\u003eLang RM, Badano LP, Mor-Avi V, et al (2015) Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr 28:1-39.e14. https://doi.org/10.1016/j.echo.2014.10.003\u003c/li\u003e\n\u003cli\u003eExpert Round Table on Echocardiography in ICU (2014) International consensus statement on training standards for advanced critical care echocardiography. Intensive Care Med 40:654\u0026ndash;666. https://doi.org/10.1007/s00134-014-3228-5\u003c/li\u003e\n\u003cli\u003eFlower L, Madhivathanan PR, Andorka M, et al (2021) Getting the most from the subcostal view: The rescue window for intensivists. 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Crit Care Med 38:819. https://doi.org/10.1097/CCM.0b013e3181c8fe7a\u003c/li\u003e\n\u003cli\u003eMaizel J, Airapetian N, Lorne E, et al (2007) Diagnosis of central hypovolemia by using passive leg raising. Intensive Care Med 33:1133\u0026ndash;1138. https://doi.org/10.1007/s00134-007-0642-y\u003c/li\u003e\n\u003cli\u003eCheong I, Otero Castro V, Brizuela M, et al (2025) Passive leg raising test to predict fluid responsiveness using the right ventricle outflow tract velocity-time integral through a subcostal view. J Ultrasound 28:19\u0026ndash;25. https://doi.org/10.1007/s40477-022-00719-7\u003c/li\u003e\n\u003cli\u003eDehbi S, Ghannam A, Elahmadi B, et al (2025) The diagnostic accuracy of the right ventricular outflow tract velocity-time integral in assessing fluid responsiveness with the passive leg-raising test. Intensive Care Med 51:1371\u0026ndash;1374. https://doi.org/10.1007/s00134-025-07974-2\u003c/li\u003e\n\u003cli\u003eSanfilippo F, Huang S, Herpain A, et al (2021) The PRICES statement: an ESICM expert consensus on methodology for conducting and reporting critical care echocardiography research studies. Intensive Care Med 47:1\u0026ndash;13. https://doi.org/10.1007/s00134-020-06262-5\u003c/li\u003e\n\u003cli\u003eMukherjee M, Rudski LG, Addetia K, et al (2025) Guidelines for the Echocardiographic Assessment of the Right Heart in Adults and Special Considerations in Pulmonary Hypertension: Recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr 38:141\u0026ndash;186. https://doi.org/10.1016/j.echo.2025.01.006\u003c/li\u003e\n\u003cli\u003eJozwiak M, Mercado P, Teboul J-L, et al (2019) What is the lowest change in cardiac output that transthoracic echocardiography can detect? Crit Care 23:116. https://doi.org/10.1186/s13054-019-2413-x\u003c/li\u003e\n\u003cli\u003eLe Gall JR, Lemeshow S, Saulnier F (1993) A new Simplified Acute Physiology Score (SAPS II) based on a European/North American multicenter study. JAMA 270:2957\u0026ndash;2963. https://doi.org/10.1001/jama.270.24.2957\u003c/li\u003e\n\u003cli\u003eVincent JL, Moreno R, Takala J, et al (1996) The SOFA (Sepsis-related Organ Failure Assessment) score to describe organ dysfunction/failure. On behalf of the Working Group on Sepsis-Related Problems of the European Society of Intensive Care Medicine. Intensive Care Med 22:707\u0026ndash;710. https://doi.org/10.1007/BF01709751\u003c/li\u003e\n\u003cli\u003eColinas Fern\u0026aacute;ndez L, Hern\u0026aacute;ndez Mart\u0026iacute;nez G, Serna Gand\u0026iacute;a MB, et al (2023) Improving echographic monitoring of hemodynamics in critically ill patients: Validation of right cardiac output measurements through the modified subcostal window. Med Intensiva 47:149\u0026ndash;156. https://doi.org/10.1016/j.medin.2022.01.006\u003c/li\u003e\n\u003cli\u003eCotella JI, Miyoshi T, Mor-Avi V, et al (2023) Normative values of the aortic valve area and Doppler measurements using two-dimensional transthoracic echocardiography: results from the Multicentre World Alliance of Societies of Echocardiography Study. Eur Heart J Cardiovasc Imaging 24:415\u0026ndash;423. https://doi.org/10.1093/ehjci/jeac220\u003c/li\u003e\n\u003cli\u003eMaizel J, Salhi A, Tribouilloy C, et al (2013) The subxiphoid view cannot replace the apical view for transthoracic echocardiographic assessment of hemodynamic status. Crit Care 17:R186. https://doi.org/10.1186/cc12869\u003c/li\u003e\n\u003cli\u003eFerrazza A, Marino B, Giusti V, et al (1990) Usefulness of Left and Right Oblique Subcostal View in the Echo-Doppler Investigation of Pulmonary Arterial Blood Flow in Patients with Chronic Obstructive Pulmonary Disease. Chest 98:286\u0026ndash;289. https://doi.org/10.1378/chest.98.2.286\u003c/li\u003e\n\u003cli\u003eG\u0026uuml;rsel G, \u0026Ouml;zdemir U, G\u0026uuml;ney T, et al (2020) The usefulness of subxiphoid view in the evaluation of acceleration time and pulmonary hypertension in ICU patients. Echocardiography 37:1345\u0026ndash;1352. https://doi.org/10.1111/echo.14822\u003c/li\u003e\n\u003cli\u003eJozwiak M, Teboul J-L (2024) Heart\u0026ndash;Lungs interactions: the basics and clinical implications. Ann Intensive Care 14:122. https://doi.org/10.1186/s13613-024-01356-5\u003c/li\u003e\n\u003cli\u003eChew MS, Aissaoui N, Balik M (2023) Echocardiography in shock. Curr Opin Crit Care 29:252\u0026ndash;258. https://doi.org/10.1097/MCC.0000000000001041\u003c/li\u003e\n\u003cli\u003eBossa MN, Berto A, Garcia-Sineriz I, et al (2025) Impact of interobserver variability of echocardiography derived clinical metrics on sample size estimation in clinical trials. Eur Heart J - Cardiovasc Imaging 26:jeae333.043. https://doi.org/10.1093/ehjci/jeae333.043\u003c/li\u003e\n\u003cli\u003eMonnet X, Teboul J-L (2017) Transpulmonary thermodilution: advantages and limits. Crit Care Lond Engl 21:147. https://doi.org/10.1186/s13054-017-1739-5\u003c/li\u003e\n\u003cli\u003eLevitov A, Marik PE (2012) Echocardiographic assessment of preload responsiveness in critically ill patients. Cardiol Res Pract 2012:819696. https://doi.org/10.1155/2012/819696\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"614\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"6\" valign=\"top\" style=\"width: 614px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTable 1: Number and percentage of measurement failures (n = 72).\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" colspan=\"4\" style=\"width: 425px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of CO\u003csub\u003eSTD\u003c/sub\u003e measurement failures (n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 128px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"4\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of CO\u003csub\u003eSC\u003c/sub\u003e measurement failures (n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e50 (69.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 128px;\"\u003e\n \u003cp\u003e5 (6.9%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e1 (1.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 128px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e11 (15.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e1 (1.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 128px;\"\u003e\n \u003cp\u003e4 (5.6%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" colspan=\"4\" style=\"width: 425px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of LVOT VTI measurement failures (n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 128px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"4\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of RVOT\u003csub\u003eSC\u003c/sub\u003e VTI measurement failures (n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e50 (69.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0,0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 128px;\"\u003e\n \u003cp\u003e5 (6,9%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0,0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e1 (1.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e1 (1.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 99px;\"\u003e\n \u003cp\u003e1 (1.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e0 (0.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e10 (13.9%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e1 (1.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 99px;\"\u003e\n \u003cp\u003e1 (1.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 128px;\"\u003e\n \u003cp\u003e2 (2.8%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" colspan=\"4\" style=\"width: 425px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of LVOTd measurement failures (n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" style=\"width: 198px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" style=\"width: 227px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of RVOT\u003csub\u003eSC\u003c/sub\u003ed measurement failures (n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e0\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" style=\"width: 198px;\"\u003e\n \u003cp\u003e52 (72.2%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" style=\"width: 227px;\"\u003e\n \u003cp\u003e4 (5.6%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" style=\"width: 198px;\"\u003e\n \u003cp\u003e14 (19.4%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" style=\"width: 227px;\"\u003e\n \u003cp\u003e2 (2.8%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eCO\u003csub\u003eSC\u003c/sub\u003e \u0026ndash; Subcostal cardiac output, CO\u003csub\u003eSTD\u003c/sub\u003e Standard cardiac output, LVOT VTI \u0026ndash; Left ventricular outflow tract velocity time integral, LVOTd \u0026ndash; Left ventricular outflow tract diameter \u0026ndash; RVOT\u003csub\u003eSC\u003c/sub\u003e VTI \u0026ndash; Subcostal right ventricular outflow tract velocity time integral, RVOT\u003csub\u003eSC\u003c/sub\u003ed \u0026ndash; Subcostal right ventricular outflow tract diameter, RVOT\u003csub\u003eSC\u003c/sub\u003ed \u0026ndash; Subcostal right ventricular outflow tract diameter.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2: Main echocardiographic data at baseline (n = 50).\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"794\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" valign=\"top\" style=\"width: 85.2735%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eEchocardiographic examination indication\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eShock diagnosis, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e15 (30.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eHypoxemia, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e5 (10.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eTherapeutic monitoring, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e13 (26.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eVolume status evaluation, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e17 (34.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" valign=\"top\" style=\"width: 85.2735%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLVEF (visual)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003e\u0026gt; 60 %, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e10 (20.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003e50 \u0026ndash; 60 %, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e15 (30.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003e40 \u0026ndash; 49 %, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e11 (22.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003e30 \u0026ndash; 39 %, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e5 (10.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003e20 \u0026ndash; 29 %, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e5 (10.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003e\u0026lt; 20 %, n %\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e4 (8.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLeft ventricular diastolic function parameters\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eMitral E/A ratio, median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e1.1 (0.8\u0026ndash;1.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eMitral E/e\u0026apos; lateral ratio, median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e5.6 (7.4\u0026ndash;10.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eMitral E-wave deceleration time (ms), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e170 (133\u0026ndash;213)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eMitral S\u0026apos; wave (cm/s), mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e10.2 \u0026plusmn; 2.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eLeft atrial volume index (mL/m\u0026sup2;), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e22.3 (18.9\u0026ndash;25.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" valign=\"top\" style=\"width: 85.2735%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRight ventricular function and structural parameters\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eTAPSE (mm), mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e21 \u0026plusmn; 4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eTricuspid S\u0026apos; wave (cm/s), mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e12.1 \u0026plusmn; 2.9\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eTricuspid regurgitation peak velocity (TRPV, m/s), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e1.8 (0.0\u0026ndash;2.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003ePulmonary acceleration time (ms), mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e104 \u0026plusmn; 28\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eRight atrial area (cm\u0026sup2;), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e14.9 (11.9\u0026ndash;18.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eRV/LV ratio, mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e0.9 \u0026plusmn; 0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eLeft ventricle eccentricity index, median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e1.0 (1.0\u0026ndash;1.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eInferior vena cava diameter (mm), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e20 (17\u0026ndash;24)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eInferior vena cava respiratory variation (%), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e15 (7\u0026ndash;31)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eEstimated systolic pulmonary arterial pressure (mmHg), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e19.4 (12.1\u0026ndash;32.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" valign=\"top\" style=\"width: 85.2735%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePericardium\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eNormal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e41 (82.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eMillimetric effusion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e8 (16.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"top\" style=\"width: 62.9431%;\"\u003e\n \u003cp\u003eCentimetric effusion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 22.461%;\"\u003e\n \u003cp\u003e1 (2.0%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" valign=\"bottom\" style=\"width: 85.2735%;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" colspan=\"2\" valign=\"top\" style=\"width: 85.2735%;\"\u003e\n \u003cp\u003eA \u0026ndash; mitral A wave, E\u0026ndash; mitral E wave, e\u0026rsquo; \u0026ndash; lateral e\u0026rsquo; mitral tissular velocity, LVEF \u0026ndash; Left ventricular\u0026nbsp;\u003cbr\u003eejection fraction, RV/LV ratio \u0026ndash; Right ventricle/Left ventricle ratio, TAPSE \u0026ndash; Tricuspid annular plane\u0026nbsp;\u003cbr\u003esystolic excursion.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3: Echocardiographic values and differences at each examination time point (n = 150).\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"682\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 198px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e\u003cstrong\u003et0 (n= 50)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e\u003cstrong\u003et1\u003csub\u003ePLR\u0026nbsp;\u003c/sub\u003e(n= 50)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e\u003cstrong\u003et2 (n= 50)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGlobal (n= 150)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 198px;\"\u003e\n \u003cp\u003eRVOT\u003csub\u003eSC\u003c/sub\u003e VTI (cm), mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e15.4 \u0026plusmn; 4.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e16.3 \u0026plusmn; 4.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e15.5 \u0026plusmn; 4.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e15.7 \u0026plusmn; 4.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 198px;\"\u003e\n \u003cp\u003eLVOT VTI (cm), mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e16.7 \u0026plusmn; 5.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e17.7 \u0026plusmn; 5.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e16.7 \u0026plusmn; 4.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e17.0 \u0026plusmn; 5.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 198px;\"\u003e\n \u003cp\u003eCO\u003csub\u003eSC\u003c/sub\u003e (L/min), mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e4.78 \u0026plusmn; 1.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e5.05 \u0026plusmn; 1.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e4.80 \u0026plusmn; 1.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e4.88 \u0026plusmn; 1.48\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 198px;\"\u003e\n \u003cp\u003eCO\u003csub\u003eSTD\u003c/sub\u003e (L/min), mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e4.87 \u0026plusmn; 1.45\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e5.11 \u0026plusmn; 1.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e4.85 \u0026plusmn; 1.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e4.94 \u0026plusmn; 1.51\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 198px;\"\u003e\n \u003cp\u003eSV\u003csub\u003eSC\u003c/sub\u003e (mL), mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e54 \u0026plusmn; 18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e57 \u0026plusmn; 20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e55 \u0026plusmn; 19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e55 \u0026plusmn; 19\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 198px;\"\u003e\n \u003cp\u003eSV\u003csub\u003eSTD\u003c/sub\u003e (mL), mean \u0026plusmn; SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e54 \u0026plusmn; 17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e57 \u0026plusmn; 19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e54 \u0026plusmn; 16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e55 \u0026plusmn; 17\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 198px;\"\u003e\n \u003cp\u003eHR\u003csub\u003eSC\u003c/sub\u003e (bpm), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e88 (76\u0026ndash;111)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e88 (74\u0026ndash;112)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e86 (75\u0026ndash;112)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e88 (75\u0026ndash;112)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 198px;\"\u003e\n \u003cp\u003eHR\u003csub\u003eSTD\u003c/sub\u003e (bpm), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e88 (75\u0026ndash;115)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e87 (74\u0026ndash;110)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e88 (75\u0026ndash;111)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e88 (75\u0026ndash;123)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 198px;\"\u003e\n \u003cp\u003eRVOT\u003csub\u003eSC\u003c/sub\u003ed (mm), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e20.8 (20.0\u0026ndash;22.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" valign=\"bottom\" style=\"width: 198px;\"\u003e\n \u003cp\u003eLVOTd (mm), median (IQR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e20.3 (19.9\u0026ndash;21.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 198px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e\u003cstrong\u003et0 (n= 50)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e\u003cstrong\u003et1\u003csub\u003ePLR\u0026nbsp;\u003c/sub\u003e(n= 50)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e\u003cstrong\u003et2 (n= 50)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGlobal (n= 150)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 198px;\"\u003e\n \u003cp\u003eVTI difference (cm), IC95%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e-1.3 (-2.0\u0026ndash;-0.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e-1.4 (-2.1\u0026ndash; -0.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e-1.2 (-1.7\u0026ndash; -0.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e-1.3 (-1.7\u0026ndash; -0.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep \u0026lt; 0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep \u0026lt; 0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep \u0026lt; 0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep \u0026lt; 0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 198px;\"\u003e\n \u003cp\u003eCO difference (L/min), IC95%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e-0.08 (-0.24\u0026ndash;0.07)\u003cu\u003e\u0026nbsp;\u003c/u\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e-0.05 (-0.23\u0026ndash;0.12)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e-0.05 (-0.24\u0026ndash;0.14)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e-0.06 (-0.19\u0026ndash;0.05)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.285\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.545\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.594\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.242\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 198px;\"\u003e\n \u003cp\u003eSV difference (mL), IC95%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e0 (-2\u0026ndash;2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e0 (-2\u0026ndash;2)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e0 (-2\u0026ndash;3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e0 (-2\u0026ndash;2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.973\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.949\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.615\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.834\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 198px;\"\u003e\n \u003cp\u003eHR difference (bpm), IC95%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e0 (-2\u0026ndash;2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e0 (-2\u0026ndash;3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e-1 (-4\u0026ndash;2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003e0 (-2\u0026ndash;2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.546\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.247\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.312\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 198px;\"\u003e\n \u003cp\u003eVOTd difference (mm), IC95%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e0.7 (0.3\u0026ndash;1.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003ep = 0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 121px;\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eCO \u0026ndash; Cardiac output, CO\u003csub\u003eSC\u003c/sub\u003e \u0026ndash; Subcostal cardiac output, CO\u003csub\u003eSTD\u003c/sub\u003e Standard cardiac output, HR\u003csub\u003eSC\u003c/sub\u003e \u0026ndash; heart rate during subcostal measurement, HR\u003csub\u003eSTD\u003c/sub\u003e \u0026ndash; heart rate during standard measurement, LVOT VTI \u0026ndash; Left ventricular outflow tract velocity time integral, LVOTd \u0026ndash; \u0026nbsp;Left ventricular outflow tract diameter, RVOT\u003csub\u003eSC\u003c/sub\u003e VTI \u0026ndash; Subcostal right ventricular outflow tract velocity time integral, RVOT\u003csub\u003eSC\u003c/sub\u003ed \u0026ndash; Subcostal right ventricular outflow tract diameter, SV \u0026ndash; Stroke volume, SV\u003csub\u003eSC\u003c/sub\u003e \u0026ndash; right subcostal stroke volume, SV\u003csub\u003eSTD\u003c/sub\u003e \u0026ndash; Standard stroke volume, VOTd\u0026ndash; Ventricular outflow tract diameter, VTI \u0026ndash; Velocity time integral\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"critical-care","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cric","sideBox":"Learn more about [Critical Care](http://ccforum.biomedcentral.com/)","snPcode":"13054","submissionUrl":"https://submission.nature.com/new-submission/13054/3","title":"Critical Care","twitterHandle":"@Crit_Care","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Echocardiography, Hemodynamic monitoring, Cardiac output, Fluid responsiveness, Subcostal window, Intensive Care Unit, Right ventricular outflow tract","lastPublishedDoi":"10.21203/rs.3.rs-9542115/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9542115/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eMeasurement of subcostal cardiac output (CO\u003csub\u003eSC\u003c/sub\u003e), using subcostal right ventricular outflow tract velocity-time integral (RVOT\u003csub\u003eSC\u003c/sub\u003e VTI) and subcostal right ventricular outflow tract diameter (RVOT\u003csub\u003eSC\u003c/sub\u003ed) remains understudied.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThe primary objective was to evaluate the agreement between standard cardiac output (CO\u003csub\u003eSTD\u003c/sub\u003e) and CO\u003csub\u003eSC\u003c/sub\u003e. Secondary objectives included calculating failure rates for window and CO acquisition, analyzing the correlation between RVOT\u003csub\u003eSC\u003c/sub\u003e and left ventricular outflow tract velocity-time integral (LVOT VTI), and determining the diagnostic performance of ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI to detect ΔLVOT VTI after passive leg raising (PLR).\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eFifty prospective complete echocardiography were performed. Agreement between CO\u003csub\u003eSC\u003c/sub\u003e and CO\u003csub\u003eSTD\u003c/sub\u003e was excellent (ICC\u0026thinsp;=\u0026thinsp;0.91, 95% CI 0.82 to 0.96; p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) with a mean difference bias (\u0026plusmn;\u0026thinsp;limit of agreement) of -0.06 L/min (-1.27 to 1.15). Correlation between RVOT\u003csub\u003eSC\u003c/sub\u003e VTI and LVOT VTI was strong (r\u0026thinsp;=\u0026thinsp;0.89, 95% CI 0.78 to 0.93; p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). While acoustic window availability was similar, CO\u003csub\u003eSC\u003c/sub\u003e had a significantly higher measurement failure rate than CO\u003csub\u003eSTD\u003c/sub\u003e (9.2%, 95% CI 5.4 to 13.1; p\u0026thinsp;=\u0026thinsp;0.01). For fluid responsiveness, the ICC for ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI vs. ΔLVOT VTI after a PLR was 0.86 (95% CI 0.76 to 0.92; p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). The area under the curve 0.98 (95% CI 0.95 to 1.00). The optimal threshold for ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI was 12.1% (Youden index), demonstrating identical performance to a 13.04% threshold (sensitivity 92.3%, specificity 97.3%) whereas the \u0026gt;\u0026thinsp;15.9% threshold yields a sensitivity of 46.2%.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe CO\u003csub\u003eSC\u003c/sub\u003e measurement shows reliable performance in critical care compared with CO\u003csub\u003eSTD\u003c/sub\u003e. ΔRVOT\u003csub\u003eSC\u003c/sub\u003e VTI accurately predicts fluid responsiveness, although measurement failure is more frequent than with the CO\u003csub\u003eSTD\u003c/sub\u003e.\u003c/p\u003e","manuscriptTitle":"Prospective evaluation of a subcostal echocardiographic cardiac output measurement in critically ill patients compared with standard transthoracic echocardiography measurement – The Right Way","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-11 16:50:54","doi":"10.21203/rs.3.rs-9542115/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"88939245144329337800908215356606265834","date":"2026-05-16T09:27:25+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-02T12:18:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"281012921614838381062181340940259204675","date":"2026-05-01T11:46:30+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-05-01T06:09:40+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-29T06:46:31+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-29T06:46:28+00:00","index":"","fulltext":""},{"type":"submitted","content":"Critical Care","date":"2026-04-27T12:44:37+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"critical-care","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cric","sideBox":"Learn more about [Critical Care](http://ccforum.biomedcentral.com/)","snPcode":"13054","submissionUrl":"https://submission.nature.com/new-submission/13054/3","title":"Critical Care","twitterHandle":"@Crit_Care","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3231bd95-97a7-4985-a824-bc420ec02b11","owner":[],"postedDate":"May 11th, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"88939245144329337800908215356606265834","date":"2026-05-16T09:27:25+00:00","index":28,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-02T12:18:24+00:00","index":19,"fulltext":""},{"type":"reviewerAgreed","content":"281012921614838381062181340940259204675","date":"2026-05-01T11:46:30+00:00","index":17,"fulltext":""},{"type":"reviewersInvited","content":"17","date":"2026-05-01T06:09:40+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-11T16:50:57+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-11 16:50:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9542115","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9542115","identity":"rs-9542115","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}