The interaction of fibrinolysis and the complement system in patients with acute pulmonary embolism, treated with ultrasound-assisted catheter-directed thrombolysis

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Draxler, Christopher D. Barrett, Justine Brodard, Elizabeth R. Maginot, and 9 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7180620/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 29 Jan, 2026 Read the published version in Thrombosis Journal → Version 1 posted 11 You are reading this latest preprint version Abstract Ultrasound-assisted catheter-directed thrombolysis (USAT) with recombinant tissue-type plasminogen activator (rt-PA) is widely used as a reperfusion approach for acute pulmonary embolism (PE). The fibrinolytic effector protease plasmin is known to be a potent activator of the complement system. The aim of this study was to better characterize the extent of complement activation during USAT, and its relationship with the fibrinolytic system. In this single-center cohort study of USAT for PE, pulmonary-arterial hemodynamic measurements were performed, and plasma samples obtained from 35 patients before treatment start and at 6 hours (during infusion of rt-PA). Hemostatic properties were evaluated with thromboelastometry and assessment of fibrinolytic markers. In addition, levels of the complement components C3a, C4a, C5a, soluble C5b-9 (sC5b-9), Ba, Bb, factor H and factor I at these time points were determined. Several complement components, including the anaphylatoxin C3a, showed a reduction during USAT. We found a positive correlation of the plasmin-antiplasmin complex (plap complex) with factor H, yet a negative correlation with both Ba and Bb, C5a and sC5b-9. The potent plasmin-inhibitor, α2-antiplasmin, displayed a positive correlation with Ba and Bb, factor I and factor H. In addition, the anaphylatoxin C5a negatively, and Ba positively predicted treatment responsiveness to USAT. In conclusion, in the setting of acute PE and reperfusion therapy with USAT, there appears to be a competing effect between plasmin-mediated complement activation and a reduction of the inflammatory trigger by resolution of obstruction and ischemia. Complement activation in PE is downregulated during USAT, an effect exceeding the complement-activating properties of plasmin. Pulmonary embolism catheter-directed thrombolysis fibrinolysis fibrinolytic potential fibrinolytic capacity inflammation complement Figures Figure 1 Introduction Acute PE represents a common cardiovascular emergency with an annual incidence of 1 in 1,000 persons. Early mortality rates of up to 30% have been described [ 1 – 4 ]. In intermediate-high and high-risk cases with right ventricular (RV) strain or even hemodynamic instability, immediate reperfusion treatment is indicated. This can be achieved with thrombolytic therapy by intravenous injection of a plasminogen activator, such as recombinant tissue-plasminogen activator, rt-PA [ 5 , 6 ]. As systemic thrombolysis is associated with a significant bleeding risk [ 7 ], catheter-directed thrombolysis is nowadays frequently used as an alternative treatment option with a reduced total dose of rt-PA. The most extensively studied option is ultrasound-assisted catheter-directed thrombolysis (USAT) using the EkoSonic™ Endovascular System (EKOS™, Boston Scientific, Marlborough, MA, USA) [ 8 , 9 ]. We have recently observed a profound variability in the treatment response to USAT [ 10 ]. In a subgroup analysis of 35 patients, we demonstrated that the endogenous fibrinolytic capacity, represented by plasmin-antiplasmin (plap) complex and D-dimer levels at 6 hours, predicted the individual treatment efficacy as indicated by a reduction in the mean pulmonary arterial pressure (PAPm) [ 11 ]. In addition, ex vivo assessment of the fibrinolytic capacity prior to initiation of USAT also predicted efficacy, which may aid in deciding for or against thrombolytic therapy in the future, or in performing a dose adjustment in patients with a particularly active or inactive fibrinolytic system. The ultimate goal of this approach will be to reduce peri-procedural complication rates and to improve efficacy and hemodynamic outcome in patients with PE [ 11 ]. Plasmin is the effector protease of the fibrinolytic system, and is now also recognized as a potent immune modulator through direct interaction with various leukocytes, parenchymal cells, components of the extracellular matrix, and soluble mediators of the immune system [ 12 ]. A large body of contemporary evidence suggests that excessive plasmin generation frequently contributes to the pathophysiology of acute and chronic inflammatory processes [ 12 ]. It is now also understood that the fibrinolytic system and the complement system closely interact with each other [ 13 ], but these interactions may be context-specific and are not fully explored in disease-specific investigations to date. Plasmin has been demonstrated to directly cleave C3 and C5 to C3a/C3b and C5a/C5b, respectively, thereby converting them into their active fragments [ 14 , 15 ]. Thus, supraphysiologic plasmin generation, as occurs during thrombolytic therapy, may promote complement activation and other non-fibrinolytic effects of plasmin, whereas complement activation, as a direct consequence of PE, may instead exhibit a generalized resolution profile due to clot resolution and reduction of the RV strain. We set out to test the general hypothesis that the large amount of plasmin generated during USAT would lead to an increase in complement activation fragments using plasma samples collected from a single-center prospective PE cohort study. Methods The B ER n A cute Pulmonary Emboli S m R E gistry ( ERASE PE) is a single-center, prospective cohort study aimed at evaluating the risks and benefits of pulmonary embolism treatment based on decisions made by the local multi-disciplinary pulmonary embolism response team (PERT). This study began in October 2017 and is carried out at Bern University Hospital. ERASE PE is registered on clinicaltrials.gov under the identifier NCT04355975 , with registration dated April 17, 2020. Study design Adult patients (18 years and older) with PE who were referred for advanced PE management were eligible for inclusion in the study. Upon arrival at the tertiary care facility, patients underwent evaluation by a skilled multidisciplinary pulmonary embolism response team (PERT), considering clinical presentation, hemodynamic status, and imaging findings. Risk assessment, treatment decisions, and administration of advanced PE therapies were available around the clock through the Pulmonary Embolism Center, overseen by the Department of Cardiology. The study protocol received approval from the local ethics committee, and all participants provided written informed consent. Study patients and treatment Patients aged 18 years or older were eligible for USAT if they had been diagnosed with acute pulmonary embolism (PE) within 14 days of symptom onset and showed evidence of proximal central or segmental filling defects indicative of PE on computed tomography angiography (CTA). Risk stratification followed the 2019 European Society of Cardiology (ESC) guidelines for PE diagnosis and management [ 6 ]. Briefly, patients were classified as high risk for early mortality if they exhibited acute hemodynamic instability and overt obstructive shock. For those without cardiogenic shock, right heart strain causing cardiac ischemia was evaluated through blood tests measuring cardiac troponin and serum brain natriuretic peptide levels, alongside imaging evidence of right heart dilation via computed tomography or transthoracic echocardiography. Symptomatic patients with either positive biomarkers or imaging signs of right heart strain were classified as intermediate-low risk, while those positive for both criteria were categorized as intermediate-high risk [ 6 ]. USAT was carried out using a standardized protocol with the EkoSonic™ Endovascular System (EKOSTM, Boston Scientific, Marlborough, USA). The EKOSTM system features a 5.4 French infusion catheter containing a coaxial ultrasonic core that delivers low-energy, non-cavitational ultrasound to disrupt fibrin fibrils in the embolus, enhancing the effectiveness of thrombolytic therapy [ 9 ]. Ultrasound energy is generated by a control unit that regulates acoustic power and monitors catheter temperature. According to protocol, bilateral EKOS catheters were inserted via a single 12 French femoral access sheath following ultrasound-guided femoral vein puncture. Prior to catheter placement, patients underwent comprehensive hemodynamic evaluation through right heart catheterization and angiographic verification of clot location. In patients with reduced mixed venous oxygen saturation (SvO2 < 45%), a bolus of recombinant tissue plasminogen activator (rt-PA) was considered. During USAT, patients received a standard dose of 10 mg rt-PA per catheter over 15 hours and were closely monitored for any hemodynamic or neurological changes in an intermediate care unit. For patients at high bleeding risk, the dosing regimen was adjusted at the operator’s discretion. Following USAT, pulmonary artery hemodynamics were measured via the EKOS™ drug delivery catheter after removing the ultrasonic core. The femoral sheath was removed four hours after completion of the thrombolytic infusion, with manual compression applied to the access site until hemostasis was achieved. Throughout the entire treatment process, full therapeutic anticoagulation with unfractionated heparin was maintained. Data collection and study endpoints Patient data were collected prospectively and managed using Research Electronic Data Capture (REDCap), a secure, web-based platform hosted by Bern University Hospital. REDCap is specifically designed to facilitate research data collection by offering: 1) a user-friendly interface for accurate and validated data entry; 2) audit trails to monitor data changes and export activities; 3) automated export functions for easy transfer of data to commonly used statistical software; and 4) capabilities for data integration and compatibility with external systems [ 16 , 17 ]. Treatment success was defined by improvement in pulmonary hypertension, assessed invasively through mean pulmonary artery pressure (PAPm) measurements taken at catheter insertion (prior to USAT) and at catheter removal (after USAT), along with a reduction in the right-to-left ventricular (RV/LV) ratio observed on day 2 following the start of USAT. Assessment of plasminogen activity Plasminogen activity was measured by the central clinical hematology laboratory at Inselspital Bern, following their standard protocol. In short, plasma samples were incubated with an excess of streptokinase to form an enzymatically active plasminogen-streptokinase complex. The streptokinase reagent includes plasminogen-poor fibrinogen to maintain a constant fibrinogen level, preventing falsely elevated plasminogen readings in plasma samples with high fibrinogen or fibrin(ogen) degradation products. The activity of the plasminogen-streptokinase/fibrinogen complex was determined by the rate of hydrolysis of the chromogenic substrate SPm41. Standard human plasma with a manufacturer-defined plasminogen activity was used as a reference, and results were expressed as a percentage of normal plasma activity. Evaluation of α2-antiplasmin activity The α2-antiplasmin activity was measured by the central clinical hematology laboratory at the hospital using their standard protocol. In brief, plasma samples were incubated with an excess amount of plasmin. The α2-antiplasmin in the sample neutralizes a corresponding amount of the added plasmin by forming plasmin–α2-antiplasmin complexes. The amount of remaining plasmin was then quantified through the conversion of a chromogenic substrate added to the test mixture. α2-antiplasmin activity was calculated using a reference curve and expressed as a percentage of normal plasma, based on standard human plasma with manufacturer-defined α2-antiplasmin activity. Assessment of plasma urokinase-type plasminogen activator (u-PA) levels Plasma levels of u-PA were measured using the TECHNOZYM u-PA ELISA Kit (Technoclone) following the manufacturer’s instructions. The assay wells were pre-coated with a monoclonal anti-u-PA antibody. After washing, the plates were incubated with a conjugated polyclonal anti-u-PA antibody for 1 hour at 37°C. Following additional washes, a substrate solution was added and incubated for 20 minutes at room temperature, after which a stop solution was applied. The absorbance was then measured at 450 nm. Evaluation of plap complex levels Plasma levels of plasmin–α2-antiplasmin (plap) complexes were measured using the DRG PAP ELISA RUO Kit (DRG Instruments, Marburg, Germany) following the manufacturer’s guidelines. Assessment of complement levels Complement analyte measurements of C3a, C4a, C5a, soluble C5b-9 (sC5b-9), Ba, Bb, factor H and factor I were performed using a Quansys Q-View Imager LS system with Quidel MicroVue complement multiplex kit, according to the manufacturer’s instructions. Increases in C3a, C4a, C5a, soluble C5b-9 (sC5b-9), Ba, Bb represent complement activation, whereas factors H and I are inhibitors [ 18 ]. Viscoelastic testing Viscoelastic whole blood analysis was conducted using Rotational Thromboelastometry (ROTEM®, Werfen France). Four different assays were performed to evaluate coagulation both before (pre-lysis) and during (at 6 hours) USAT treatment. The EXTEM assay activates the extrinsic coagulation pathway via tissue factor. The INTEM assay triggers the intrinsic pathway using negatively charged surfaces such as kaolin or ellagic acid. The FIBTEM assay isolates fibrinogen function by adding cytochalasin, which inhibits platelet microfilaments, thereby removing the influence of platelet-driven clot retraction. Since all patients received heparin therapy, the HEPTEM assay was also included; it incorporates heparinase to neutralize heparin’s effects. The parameters measured included clotting time (CT, seconds), clot formation time (CFT, seconds), α-angle (degrees) reflecting fibrin polymerization rate, clot strength at 10 minutes (A10, mm), maximum clot firmness (MCF, mm), and maximum clot lysis (ML, %) as a marker of fibrinolysis [ 19 ]. Statistical analysis Patient characteristics—including medical history, symptoms, vital signs, catheterization data, and discharge details from the initial hospitalization—were summarized using counts with percentages, means with standard deviations, or medians with interquartile ranges (IQR). Correlation analyses were conducted using Spearman’s correlation coefficient, adjusted for rt-PA dosage. The adjusted Spearman rank correlations were calculated following the method described by Liu et al [ 20 ]. Complement components were evaluated for their predictive value using generalized linear models to examine their relationship with the change in mean pulmonary artery pressure (PAPm) between catheter placement and removal. These models were adjusted for the rt-PA dose administered during USAT. The same modeling approach was used to investigate the association between these hemostatic markers and the reduction in the right-to-left ventricular (RV/LV) ratio post-lysis compared to the initial RV/LV ratio measured on the CTA scan at PE diagnosis. To obtain robust standard errors and account for possible deviations from normality, bootstrapping with 1,000 replications was employed for variance-covariance matrix estimation. This resampling technique repeatedly samples with replacement from the original data and recalculates model estimates for each iteration, improving the accuracy of standard error and confidence interval estimates. All statistical analyses were conducted using Stata 17 (StataCorp LLC, College Station, TX, USA). A p-value below 0.05 was considered statistically significant. Figures were created using GraphPad Prism 10.1.2 (GraphPad Software, La Jolla, CA, USA). Results Baseline and procedural characteristics The baseline characteristics of the study cohort are displayed in Table 1 . The vast majority of patients (89%) presented with an intermediate-high risk PE according to the ESC classification [ 6 ], while the remaining 11% of individuals were classified as high-risk PE patients. Sixty percent of the patients were male. Among the identified risk factors for venous thromboembolism, 11% of cases were associated with a prior COVID-19 infection, 20% of patients had diabetes, and another 20% were active smokers. Approximately one-third had a history of PE or deep vein thrombosis. Additionally, one patient each (3%) was bedridden, using hormonal contraceptives, had recently undergone major surgery, or had an active malignancy. Details of the procedure, including right heart catheterization measurements and rt-PA dosing and infusion duration, are provided in Supplementary Appendix Table 1 . Notably, no reperfusion therapies other than ultrasound-assisted thrombolysis (USAT) and anticoagulation—such as interventional or surgical embolectomy—were employed in this cohort. USAT was administered using rt-PA as the sole thrombolytic agent. In one case, a 5 mg bolus of rt-PA per catheter was given prior to continuous infusion. The total rt-PA dose was 20 mg in 80% of patients, 15 mg in 11%, and 10 mg in 9%. Table 1 Baseline characteristics n = 35 PE classification of risk (ESC) - low 0 (0%) - intermediate-low 0 (0%) - intermediate-high 31 (89%) - high 4 (11%) Age 64.3 ± 11.6 Sex (Male) 21 (60%) Height (cm) 171.5 ± 10.5 Weight (kg) 85.6 ± 17.5 Body mass index (kg/m²) 29.1 ± 5.3 COVID associated 4 (11%) Diabetes 7 (20%) Diabetes treatment n = 7, - diet 1 (14%) - oral treatment 5 (71%) - insulin 1 (14%) Glomerular filtration rate (mL/min(1.73m 2 ) 74.8 ± 16.7 - eGFR > 60 mL/min(1.73m 2 ) n = 28 (80%) - eGFR 30–60 mL/min(1.73m 2 ) n = 7 (20%) - eGFR < 30 mL/min(1.73m 2 ) n = 0 (0%) Dyslipidemia 5 (14%) COPD 1 (3%) Other lung disease 3 (9%) Tobacco consumption n = 30, - active 6 (20%) - ex-smoker 9 (30%) - never-smoker 15 (50%) Alcohol abuse 2 (6%) Liver disease 0 (0%) Major surgery within 4 weeks 1 (3%) Bedridden > 3 days 1 (3%) Coronary artery disease 0 (0%) Previous percutaneous intervention 0 (0%) Previous stroke 0 (0%) Previous Hx of myocardial infarction 0 (0%) Previous Hx of permanent PM / ICD / CRT 0 (0%) Previous PE 4 (11%) Previous deep vein thrombosis 7 (20%) Previous cardiac surgery 0 (0%) Current bleeding 0 (0%) Previous bleeding 0 (0%) Bleeding diathesis (known) 0 (0%) Current pregnancy 0 (0%) Recent delivery (< 90 days) 0 (0%) Contraception 1 (3%) Previous cancer 2 (6%) Active malignancy 1 (3%) - Active metastatic cancer 1 (3%) USAT results in reduced complement activation fragment levels The complement activation fragments C3a and Ba displayed a significant reduction during USAT compared with baseline, with a concomitant small but significant reduction in complement control protein factors I and H (Fig. 1 ). Other parameters of the complement system were not affected by the treatment ( Supplementary Appendix Table 2. ) Table 2 Fibrinolytic markers correlate with complement components at t = 6h (Spearman correlation adjusted for rt-PA dose, n = 35; only significant correlations displayed) parameter rho p-value α2-antiplasmin vs Bb 0.5873096 <0.001 plap complex vs Ba -0.4800978 0.004 α2-antiplasmin vs Ba 0.4820493 0.006 plap complex vs Bb -0.4590815 0.006 plap complex vs C5a -0.4299794 0.011 α2-antiplasmin vs factor I 0.3864462 0.032 α2-antiplasmin vs factor H 0.3854377 0.032 plap complex vs factor H 0.3651771 0.043 plap complex vs sC5b-9 -0.3399542 0.049 Fibrinolytic markers correlate with complement components during USAT When evaluating the correlative interaction of fibrinolytic markers and complement components, we found a positive correlation of the plap complex with factor H. Conversely, we observed a negative correlation of the plap complex with both Ba and Bb. A negative correlation of the plap complex was also evident with C5a and sC5b-9. The potent plasmin-inhibitor α2-antiplasmin displayed a positive correlation with Ba and Bb, factor I and factor H (Table 2 ). The anaphylatoxin C5a negatively predicts treatment responsiveness to USAT Complement components were assessed during lysis (t = 6h) for their capacity to predict treatment responsiveness (Table 3 ). The anaphylatoxin C5a positively predicted post-thrombolysis PAPm controlling for pre-lysis PAPm and rt-PA dose, hence acting as a negative predictor for treatment responsiveness. Similarly, C5a evaluated before start of USAT also negatively predicted treatment responsiveness represented by PAPm reduction (Table 4 ). With respect to a reduction in the RV/LV ratio, none of the assessed complement components predicted the reduction in response to USAT if assessed during lysis ( Supplementary Appendix Table 3 ). In turn, Ba evaluated before treatment start acted as a negative predictor for a reduction in RV/LV ratio after USAT ( Supplementary Appendix Table 4 ). Table 3 Complement components assessed during lysis (t = 6h) predict post-thrombolysis PAPm controlling for pre-lysis PAPm and rt-PA dose (n = 35) parameter bootstrap coefficient (95% CI) p-value C5a 0.55307 [0.11900 to 0.98713] (n = 29) 0.013 Bb 7.87482 [-1.80532 to 17.55495] (n = 29) 0.11 C4a -0.00587 [-0.01544 to 0.00369] (n = 29) 0.23 BA 0.01011 [-0.00690 to 0.02712] (n = 29) 0.24 sC5b-9 0.00603 [-0.01035 to 0.02241] (n = 29) 0.47 factor H 0.00971 [-0.02526 to 0.04467] (n = 29) 0.59 C3a -0.01423 [-0.07767 to 0.04920] (n = 29) 0.66 factor I 0.00007 [-0.00029 to 0.00043] (n = 29) 0.70 Table 4 Complement components assessed before treatment start predict post-thrombolysis PAPm controlling for pre-lysis PAPm and rt-PA dose (n = 35) parameter bootstrap coefficient (95% CI) p-value C5a 0.57096 [0.13231 to 1.00960] (n = 29) 0.011 Bb 7.03402 [-1.58194 to 15.64999] (n = 29) 0.12 sC5b-9 0.00798 [-0.00339 to 0.01935] (n = 29) 0.17 factor I -0.00019 [-0.00060 to 0.00022] (n = 29) 0.37 Ba 0.00499 [-0.00825 to 0.01824] (n = 29) 0.46 C4a -0.00285 [-0.01058 to 0.00487] (n = 29) 0.47 C3a -0.01173 [-0.05653 to 0.03307] (n = 29) 0.61 factor H 0.00458 [-0.04227 to 0.05144] (n = 29) 0.85 Discussion We have previously demonstrated a significant variability in the treatment efficacy of USAT in acute PE [ 10 ]. In a subsequent subgroup analysis, we showed that the endogenous fibrinolytic capacity assessed during ongoing thrombolysis, as well as the fibrinolytic potential evaluated before treatment initiation, predicted the individual treatment responsiveness as indicated by a reduction in PAPm [ 11 ] An unbalanced expression of complement components, regulators and receptors has previously been reported in patients with symptomatic PE [ 21 ]. Moreover, the extent of complement activation has been associated with RV dysfunction and PE severity [ 22 ]. In this investigation, we aimed to evaluate changes in circulating levels of various complement components in the setting of acute PE and subsequent USAT, given the known interaction between plasmin and the complement system in various clinical scenarios [ 13 ]. Speculating that the supraphysiological plasmin activity achieved with thrombolytic therapy might also enhance complement activation, we obtained the following results: Rather than an increase, USAT resulted in a reduction of two complement activation fragments (C3a, Ba) and a small but significant reduction of complement control proteins (factors I and H). When evaluating the correlative interaction of fibrinolytic markers and complement components, we found a positive correlation of the plap complex, representing plasmin generation, with factor H. Conversely, we observed a negative correlation of the plap complex with both Ba and Bb. Importantly, a negative correlation of the plap complex was also evident with C5a and sC5b-9. The potent plasmin-inhibitor α2-antiplasmin displayed a positive correlation with Ba, Bb, factor I and factor H. Levels of the anaphylatoxin C5a, evaluated either before or during USAT, negatively predicted treatment responsiveness, represented by a reduction in PAPm (i.e. positively predicted post-thrombolysis PAPm controlling for pre-lysis PAPm and rt-PA dose). Curiously, the plap complex, a marker of plasmin generation, correlated negatively with C5a, despite plasmin being known as a potent activator of C5 [ 23 , 24 ]. This suggests that the therapeutic effects of plasmin with a resulting reduction in RV strain [ 10 ] and concomitant reduced C5 activation stimulus may exceed its C5-activating properties in the setting of USAT for PE. sC5b-9, the final product of the complement cascade, also correlated negatively with the plap complex. In addition, circulating levels of various complement components and their regulators are diminished as a result of USAT. Thus, while supraphysiologic plasmin generation, as occurring during thrombolytic therapy, may promote complement activation and other non-fibrinolytic effects of plasmin, complement activation as a direct consequence of PE is attenuated. This is most likely due to the resolution of clot burden and ischemia, as well as the reduction of RV strain, resulting in less overall pathophysiologic stress to the patient. Consistent with this observation, C5a acted as a negative predictor of treatment response, indicating that increased treatment response actually results in decreased complement system activity and a reduction in circulating complement components. Hence, C5a appears to be a marker of treatment response, rather than of plasmin generation per se. In contrast, C3a and sC5b-9 did not predict treatment response, which may be related to differences in abundance, regulatory control, and half-life [ 25 ]. Levels of C3 are much higher than those of C5, hence baseline and active levels of C3a are higher than C5a. The half-lives of C3a and C5a are only a few minutes, while the half-life of sC5b-9 is several hours. Hence, sC5b-9, while reflecting C5 cleavage, is more of a global activation marker, rather than a real-time measurement of changes in the complement cascade in that exact moment. These findings are further corroborated by the observed negative correlation of the plap complex with Ba and Bb, and its positive correlation with factors I and H. In contrast, a positive correlation can be observed for Ba and Bb with α2-antiplasmin, the central plasmin inhibitor that is consumed as a result of plasmin generation and plap complex formation [ 11 ]. Cleavage of factor B occurs during the activation of the alternative pathway, resulting in the fragments Ba and Bb. Bb then forms a part of the C3 convertase. In turn, factors I and H inhibit the deposition of C3b on host cells, thereby regulating the alternative pathway [ 26 ]. The observed reduction of the control proteins factors I and H in parallel with C3a suggests, that the resolving process of PE triggers or aids factors I and H in their capacity to downregulate complement. The exact mechanism behind this curious observation remains to be elucidated. Of particular interest in this context is also the role of the alternative pathway. Ba and Bb correlated with the plap complex and α2-antiplasmin, and Ba was reduced during USAT as well. The alternative pathway is constantly active, so loss of regulation may occur in the critically ill PE patient, and this regulatory ability may be restored when PE is dissolved by plasmin, leading to reduced Ba. Similarly, ischemia is thought to trigger alternative pathway activation, as demonstrated by Ganter et al [ 27 ]. Likewise, resolution of ischemia may resolve this alternative pathway activation through restoration of regulatory pathway homeostasis. We have previously suggested that patients may benefit from a dose adjustment of the thrombolytic agent based on the individual predicted treatment responsiveness [ 11 ].The ideal thrombolytic dose may allow an optimal compromise of achieving treatment efficacy and clearance of the inflammatory trigger, while at the same time limiting the known pro-inflammatory effects of plasmin [ 12 ] to a minimum. An individualized treatment approach is therefore the goal of our ongoing investigation, and a validation study to establish the optimal markers to predict individual treatment responsiveness is currently underway. With respect to the capacity of circulating C5a, assessed prior to USAT initiation, to predict treatment response, a mechanistic involvement can be speculated. However, whether modulation of the complement system itself could be beneficial in acute PE, as previously suggested [ 22 ], remains elusive and requires further investigation. In summary, in the setting of acute PE and reperfusion therapy with USAT, there appears to be a competing effect between plasmin-mediated activation of inflammation and a reduction of the inflammatory trigger by resolution of pulmonary vascular obstruction and ischemia, with consequent reduction of PAPm and RV strain. According to our findings, complement activation in PE is downregulated in response to USAT, an effect that exceeds the complement-activating properties of plasmin. Limitations Several limitations of this study should be noted. First, this investigation was derived from a pilot study and may be underpowered to draw definitive conclusions. Second, this was a single-center study, and our results require external validation in other centers/populations to confirm that our findings are broadly applicable to patients with acute PE. Third, a control group of PE patients treated with anticoagulation alone could not be provided, which may inform us about levels of fibrinolytic proteases/inhibitors and complement components in PE patients not receiving USAT. Finally, the assays and parameters used are not currently approved for clinical use or standardized to guide treatment decisions in this indication. Abbreviations CTA computed tomography angiography scan ESC European Society of Cardiology LV right ventricle PAPm mean pulmonary arterial pressure PE pulmonary embolism PERT pulmonary embolism response team plap plasmin-antiplasmin REDCap Research Electronic Data Capture rt-PA recombinant tissue-type plasminogen activator RV right ventricle sC5b-9 soluble C5b-9 u-PA urokinase-type plasminogen activator USAT Ultrasound-assisted catheter-directed thrombolysis Declarations Ethics approval and consent to participate The study protocol was approved by the local ethics committee and all patients provided written informed consent for study participation. Consent for publication Not applicable. Availability of data and materials The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. Competing interests S. Stortecky reports research grants to the institution from Edwards Lifesciences, Medtronic, Abbott, Boston Scientific and has a consulting contract with Inari Medical outside the submitted work. None of the authors have any competing interest to declare with respect to this manuscript. Funding ERASE PE is sponsored by intramural study grants provided by the Swiss Cardiovascular Center Bern. Laboratory analyses were funded through a project grant obtained from the Bern Center of Precision Medicine, Department of Biomedical Research, University of Bern. Authors' contributions DFD, CDB, and SS designed the project and prepared the protocols. CDB, ERM, HH, CBK and RLM developed and performed the laboratory assays. DFD and SS recruited patients and SS collected the clinical data. KC and DH performed the statistical analyses. DFD and CDB prepared the manuscript. All authors reviewed the manuscript and provided expert evaluation. Acknowledgements Not applicable. 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Harris, P.A., et al., Research electronic data capture (REDCap)--a metadata-driven methodology and workflow process for providing translational research informatics support. J Biomed Inform, 2009. 42 (2): p. 377-81. Harris, P.A., et al., The REDCap consortium: Building an international community of software platform partners. J Biomed Inform, 2019. 95 : p. 103208. Barrett, C.D., et al., Hyperfibrinolysis is Associated with Complement Activation Following Trauma. Thromb Haemost, 2025. Drotarova, M., et al., Basic Principles of Rotational Thromboelastometry (ROTEM((R))) and the Role of ROTEM-Guided Fibrinogen Replacement Therapy in the Management of Coagulopathies. Diagnostics (Basel), 2023. 13 (20). Liu, Q., et al., Covariate-adjusted Spearman's rank correlation with probability-scale residuals. Biometrics, 2018. 74 (2): p. 595-605. Lv, W., et al., Characteristics of the complement system gene expression deficiency in patients with symptomatic pulmonary embolism. Thromb Res, 2013. 132 (1): p. e54-7. Rostoff, P., et al., Complement activation is associated with right ventricular dysfunction and the severity of pulmonary embolism: links with prothrombotic state. J Thorac Dis, 2024. 16 (5): p. 3181-3191. Amara, U., et al., Molecular intercommunication between the complement and coagulation systems. J Immunol, 2010. 185 (9): p. 5628-36. Foley, J.H., B.L. Walton, and M.M. Aleman, Complement activation in arterial and venous thrombosis is mediated by plasmin. EBioMedicine, 2016. 5 : p. 175-182. Ayano, M. and T. Horiuchi, Complement as a Biomarker for Systemic Lupus Erythematosus. Biomolecules, 2023. 13 (2). Morgan, B.P., et al., Complement: central to innate immunity and bridging to adaptive responses. Immunol Lett, 2005. 97 (2): p. 171-9. Ganter, M.T., et al., Role of the alternative pathway in the early complement activation following major trauma. Shock, 2007. 28 (1): p. 29-34. Additional Declarations Competing interest reported. S. Stortecky reports research grants to the institution from Edwards Lifesciences, Medtronic, Abbott, Boston Scientific and has a consulting contract with Inari Medical outside the submitted work. None of the authors have any competing interest to declare with respect to this manuscript. Supplementary Files DraxleretalUSATcomplementsupplementalmaterial.docx Cite Share Download PDF Status: Published Journal Publication published 29 Jan, 2026 Read the published version in Thrombosis Journal → Version 1 posted Editorial decision: Revision requested 11 Nov, 2025 Reviews received at journal 23 Oct, 2025 Reviews received at journal 04 Oct, 2025 Reviews received at journal 27 Sep, 2025 Reviewers agreed at journal 24 Sep, 2025 Reviewers agreed at journal 22 Sep, 2025 Reviewers agreed at journal 09 Sep, 2025 Reviewers invited by journal 08 Sep, 2025 Editor assigned by journal 22 Jul, 2025 Submission checks completed at journal 22 Jul, 2025 First submitted to journal 21 Jul, 2025 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-7180620","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":512753208,"identity":"b3a419f6-f173-4c5a-bd27-6cad96f82192","order_by":0,"name":"Dominik F. Draxler","email":"data:image/png;base64,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","orcid":"","institution":"Inselspital, University of Bern","correspondingAuthor":true,"prefix":"","firstName":"Dominik","middleName":"F.","lastName":"Draxler","suffix":""},{"id":512753209,"identity":"557cc88b-339a-442d-bdc7-bad13ad05a87","order_by":1,"name":"Christopher D. Barrett","email":"","orcid":"","institution":"University of Nebraska Medical Center","correspondingAuthor":false,"prefix":"","firstName":"Christopher","middleName":"D.","lastName":"Barrett","suffix":""},{"id":512753210,"identity":"9c3d2d10-d0fe-4dc1-9ed1-3e3b689c9239","order_by":2,"name":"Justine Brodard","email":"","orcid":"","institution":"University of Bern","correspondingAuthor":false,"prefix":"","firstName":"Justine","middleName":"","lastName":"Brodard","suffix":""},{"id":512753211,"identity":"c77f6431-231b-4b13-a233-de85219073f9","order_by":3,"name":"Elizabeth R. Maginot","email":"","orcid":"","institution":"University of Nebraska Medical Center","correspondingAuthor":false,"prefix":"","firstName":"Elizabeth","middleName":"R.","lastName":"Maginot","suffix":""},{"id":512753216,"identity":"29ac3074-75e7-446a-879c-988ad405907b","order_by":4,"name":"Konstantina Chalkou","email":"","orcid":"","institution":"University of Bern","correspondingAuthor":false,"prefix":"","firstName":"Konstantina","middleName":"","lastName":"Chalkou","suffix":""},{"id":512753217,"identity":"b8becd38-95bc-40e4-95c4-eeaead6709ae","order_by":5,"name":"Heidi Ho","email":"","orcid":"","institution":"Monash University","correspondingAuthor":false,"prefix":"","firstName":"Heidi","middleName":"","lastName":"Ho","suffix":""},{"id":512753218,"identity":"bb79edba-1e39-4646-a95b-e7fab5820d25","order_by":6,"name":"Charithani B Keragala","email":"","orcid":"","institution":"Monash University","correspondingAuthor":false,"prefix":"","firstName":"Charithani","middleName":"B","lastName":"Keragala","suffix":""},{"id":512753219,"identity":"b4d6307c-5fac-4379-a444-0882b35f7adf","order_by":7,"name":"Dik Heg","email":"","orcid":"","institution":"University of Bern","correspondingAuthor":false,"prefix":"","firstName":"Dik","middleName":"","lastName":"Heg","suffix":""},{"id":512753220,"identity":"9612b90d-09be-4d25-a45c-48290750e254","order_by":8,"name":"Johanna A. Kremer Hovinga","email":"","orcid":"","institution":"University of Bern","correspondingAuthor":false,"prefix":"","firstName":"Johanna","middleName":"A. Kremer","lastName":"Hovinga","suffix":""},{"id":512753221,"identity":"62624675-0294-457b-b5ca-e4a45d1764b6","order_by":9,"name":"Ernest E. Moore","email":"","orcid":"","institution":"University of Colorado Anschutz Medical Campus","correspondingAuthor":false,"prefix":"","firstName":"Ernest","middleName":"E.","lastName":"Moore","suffix":""},{"id":512753222,"identity":"4e078d78-7c9e-4c5d-a32c-ec235c97753f","order_by":10,"name":"Robert L. Medcalf","email":"","orcid":"","institution":"Monash University","correspondingAuthor":false,"prefix":"","firstName":"Robert","middleName":"L.","lastName":"Medcalf","suffix":""},{"id":512753223,"identity":"1ed2d51c-c4e7-44ab-ae5d-616a3473c3e5","order_by":11,"name":"Anne Angelillo-Scherrer","email":"","orcid":"","institution":"University of Bern","correspondingAuthor":false,"prefix":"","firstName":"Anne","middleName":"","lastName":"Angelillo-Scherrer","suffix":""},{"id":512753224,"identity":"b2981c34-ba14-4469-b16c-1db60af49eb3","order_by":12,"name":"Stefan Stortecky","email":"","orcid":"","institution":"Inselspital, University of Bern","correspondingAuthor":false,"prefix":"","firstName":"Stefan","middleName":"","lastName":"Stortecky","suffix":""}],"badges":[],"createdAt":"2025-07-21 20:08:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7180620/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7180620/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12959-026-00830-3","type":"published","date":"2026-01-29T15:58:20+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":91307791,"identity":"12f7c40b-b349-431e-972e-92b3a85a938a","added_by":"auto","created_at":"2025-09-15 06:40:37","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":75170,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eUSAT alters levels of complement components in patients with acute PE\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eComplement components were evaluated before treatment start (pre-lysis) and during USAT (t=6h). USAT resulted in a significant reduction of circulating C3a (\u003cstrong\u003eA\u003c/strong\u003e), Ba (\u003cstrong\u003eB\u003c/strong\u003e), factor I (\u003cstrong\u003eC\u003c/strong\u003e), and factor H (\u003cstrong\u003eD\u003c/strong\u003e).\u003c/p\u003e\n\u003cp\u003eData expressed as median ± 95% CI, differences were evaluated with a Wilcoxon signed-rank test for individual comparison between groups, n=35, * denotes p\u0026lt;0.05\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7180620/v1/9815ead04563272c9cf2c386.jpeg"},{"id":101690431,"identity":"b978bfac-e658-4d6a-b377-aad0e1e9e5b9","added_by":"auto","created_at":"2026-02-02 16:02:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1316045,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7180620/v1/b74e8a62-3421-4552-9ff5-fb84c29c786d.pdf"},{"id":91308156,"identity":"17d263f7-0b1e-4f90-bf4a-caf58cd9f0d3","added_by":"auto","created_at":"2025-09-15 06:48:37","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":21939,"visible":true,"origin":"","legend":"","description":"","filename":"DraxleretalUSATcomplementsupplementalmaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-7180620/v1/008cca39d774173d2b919603.docx"}],"financialInterests":"Competing interest reported. S. Stortecky reports research grants to the institution from Edwards Lifesciences, Medtronic, Abbott, Boston Scientific and has a consulting contract with Inari Medical outside the submitted work. \nNone of the authors have any competing interest to declare with respect to this manuscript.","formattedTitle":"The interaction of fibrinolysis and the complement system in patients with acute pulmonary embolism, treated with ultrasound-assisted catheter-directed thrombolysis","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAcute PE represents a common cardiovascular emergency with an annual incidence of 1 in 1,000 persons. Early mortality rates of up to 30% have been described [\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e–\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. In intermediate-high and high-risk cases with right ventricular (RV) strain or even hemodynamic instability, immediate reperfusion treatment is indicated. This can be achieved with thrombolytic therapy by intravenous injection of a plasminogen activator, such as recombinant tissue-plasminogen activator, rt-PA [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. As systemic thrombolysis is associated with a significant bleeding risk [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], catheter-directed thrombolysis is nowadays frequently used as an alternative treatment option with a reduced total dose of rt-PA. The most extensively studied option is ultrasound-assisted catheter-directed thrombolysis (USAT) using the EkoSonic™ Endovascular System (EKOS™, Boston Scientific, Marlborough, MA, USA) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eWe have recently observed a profound variability in the treatment response to USAT [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In a subgroup analysis of 35 patients, we demonstrated that the endogenous fibrinolytic capacity, represented by plasmin-antiplasmin (plap) complex and D-dimer levels at 6 hours, predicted the individual treatment efficacy as indicated by a reduction in the mean pulmonary arterial pressure (PAPm) [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. In addition, \u003cem\u003eex vivo\u003c/em\u003e assessment of the fibrinolytic capacity prior to initiation of USAT also predicted efficacy, which may aid in deciding for or against thrombolytic therapy in the future, or in performing a dose adjustment in patients with a particularly active or inactive fibrinolytic system. The ultimate goal of this approach will be to reduce peri-procedural complication rates and to improve efficacy and hemodynamic outcome in patients with PE [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e\u003cp\u003ePlasmin is the effector protease of the fibrinolytic system, and is now also recognized as a potent immune modulator through direct interaction with various leukocytes, parenchymal cells, components of the extracellular matrix, and soluble mediators of the immune system [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. A large body of contemporary evidence suggests that excessive plasmin generation frequently contributes to the pathophysiology of acute and chronic inflammatory processes [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. It is now also understood that the fibrinolytic system and the complement system closely interact with each other [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], but these interactions may be context-specific and are not fully explored in disease-specific investigations to date. Plasmin has been demonstrated to directly cleave C3 and C5 to C3a/C3b and C5a/C5b, respectively, thereby converting them into their active fragments [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Thus, supraphysiologic plasmin generation, as occurs during thrombolytic therapy, may promote complement activation and other non-fibrinolytic effects of plasmin, whereas complement activation, as a direct consequence of PE, may instead exhibit a generalized resolution profile due to clot resolution and reduction of the RV strain. We set out to test the general hypothesis that the large amount of plasmin generated during USAT would lead to an increase in complement activation fragments using plasma samples collected from a single-center prospective PE cohort study.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eThe B\u003cspan type=\"BoldItalicUnderline\" class=\"BoldItalicUnderline\" name=\"Emphasis\"\u003eER\u003c/span\u003en \u003cspan type=\"BoldItalicUnderline\" class=\"BoldItalicUnderline\" name=\"Emphasis\"\u003eA\u003c/span\u003ecute Pulmonary Emboli\u003cspan type=\"BoldItalicUnderline\" class=\"BoldItalicUnderline\" name=\"Emphasis\"\u003eS\u003c/span\u003em R\u003cspan type=\"BoldItalicUnderline\" class=\"BoldItalicUnderline\" name=\"Emphasis\"\u003eE\u003c/span\u003egistry (\u003cspan type=\"BoldItalicUnderline\" class=\"BoldItalicUnderline\" name=\"Emphasis\"\u003eERASE\u003c/span\u003e PE) is a single-center, prospective cohort study aimed at evaluating the risks and benefits of pulmonary embolism treatment based on decisions made by the local multi-disciplinary pulmonary embolism response team (PERT). This study began in October 2017 and is carried out at Bern University Hospital. ERASE PE is registered on clinicaltrials.gov under the identifier \u003cb\u003eNCT04355975\u003c/b\u003e, with registration dated April 17, 2020.\u003c/p\u003e\u003cp\u003e\u003cb\u003eStudy design\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAdult patients (18 years and older) with PE who were referred for advanced PE management were eligible for inclusion in the study. Upon arrival at the tertiary care facility, patients underwent evaluation by a skilled multidisciplinary pulmonary embolism response team (PERT), considering clinical presentation, hemodynamic status, and imaging findings. Risk assessment, treatment decisions, and administration of advanced PE therapies were available around the clock through the Pulmonary Embolism Center, overseen by the Department of Cardiology. The study protocol received approval from the local ethics committee, and all participants provided written informed consent.\u003c/p\u003e\u003cp\u003e\u003cb\u003eStudy patients and treatment\u003c/b\u003e\u003c/p\u003e\u003cp\u003ePatients aged 18 years or older were eligible for USAT if they had been diagnosed with acute pulmonary embolism (PE) within 14 days of symptom onset and showed evidence of proximal central or segmental filling defects indicative of PE on computed tomography angiography (CTA). Risk stratification followed the 2019 European Society of Cardiology (ESC) guidelines for PE diagnosis and management [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eBriefly, patients were classified as high risk for early mortality if they exhibited acute hemodynamic instability and overt obstructive shock. For those without cardiogenic shock, right heart strain causing cardiac ischemia was evaluated through blood tests measuring cardiac troponin and serum brain natriuretic peptide levels, alongside imaging evidence of right heart dilation via computed tomography or transthoracic echocardiography. Symptomatic patients with either positive biomarkers or imaging signs of right heart strain were classified as intermediate-low risk, while those positive for both criteria were categorized as intermediate-high risk [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eUSAT was carried out using a standardized protocol with the EkoSonic™ Endovascular System (EKOSTM, Boston Scientific, Marlborough, USA). The EKOSTM system features a 5.4 French infusion catheter containing a coaxial ultrasonic core that delivers low-energy, non-cavitational ultrasound to disrupt fibrin fibrils in the embolus, enhancing the effectiveness of thrombolytic therapy [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eUltrasound energy is generated by a control unit that regulates acoustic power and monitors catheter temperature. According to protocol, bilateral EKOS catheters were inserted via a single 12 French femoral access sheath following ultrasound-guided femoral vein puncture. Prior to catheter placement, patients underwent comprehensive hemodynamic evaluation through right heart catheterization and angiographic verification of clot location. In patients with reduced mixed venous oxygen saturation (SvO2 \u0026lt; 45%), a bolus of recombinant tissue plasminogen activator (rt-PA) was considered.\u003c/p\u003e\u003cp\u003eDuring USAT, patients received a standard dose of 10 mg rt-PA per catheter over 15 hours and were closely monitored for any hemodynamic or neurological changes in an intermediate care unit. For patients at high bleeding risk, the dosing regimen was adjusted at the operator’s discretion. Following USAT, pulmonary artery hemodynamics were measured via the EKOS™ drug delivery catheter after removing the ultrasonic core. The femoral sheath was removed four hours after completion of the thrombolytic infusion, with manual compression applied to the access site until hemostasis was achieved. Throughout the entire treatment process, full therapeutic anticoagulation with unfractionated heparin was maintained.\u003c/p\u003e\u003cp\u003e\u003cb\u003eData collection and study endpoints\u003c/b\u003e\u003c/p\u003e\u003cp\u003ePatient data were collected prospectively and managed using Research Electronic Data Capture (REDCap), a secure, web-based platform hosted by Bern University Hospital. REDCap is specifically designed to facilitate research data collection by offering: 1) a user-friendly interface for accurate and validated data entry; 2) audit trails to monitor data changes and export activities; 3) automated export functions for easy transfer of data to commonly used statistical software; and 4) capabilities for data integration and compatibility with external systems [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTreatment success was defined by improvement in pulmonary hypertension, assessed invasively through mean pulmonary artery pressure (PAPm) measurements taken at catheter insertion (prior to USAT) and at catheter removal (after USAT), along with a reduction in the right-to-left ventricular (RV/LV) ratio observed on day 2 following the start of USAT.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAssessment of plasminogen activity\u003c/b\u003e\u003c/p\u003e\u003cp\u003ePlasminogen activity was measured by the central clinical hematology laboratory at Inselspital Bern, following their standard protocol. In short, plasma samples were incubated with an excess of streptokinase to form an enzymatically active plasminogen-streptokinase complex. The streptokinase reagent includes plasminogen-poor fibrinogen to maintain a constant fibrinogen level, preventing falsely elevated plasminogen readings in plasma samples with high fibrinogen or fibrin(ogen) degradation products. The activity of the plasminogen-streptokinase/fibrinogen complex was determined by the rate of hydrolysis of the chromogenic substrate SPm41. Standard human plasma with a manufacturer-defined plasminogen activity was used as a reference, and results were expressed as a percentage of normal plasma activity.\u003c/p\u003e\u003cp\u003e\u003cb\u003eEvaluation of α2-antiplasmin activity\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe α2-antiplasmin activity was measured by the central clinical hematology laboratory at the hospital using their standard protocol. In brief, plasma samples were incubated with an excess amount of plasmin. The α2-antiplasmin in the sample neutralizes a corresponding amount of the added plasmin by forming plasmin–α2-antiplasmin complexes. The amount of remaining plasmin was then quantified through the conversion of a chromogenic substrate added to the test mixture. α2-antiplasmin activity was calculated using a reference curve and expressed as a percentage of normal plasma, based on standard human plasma with manufacturer-defined α2-antiplasmin activity.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAssessment of plasma urokinase-type plasminogen activator (u-PA) levels\u003c/b\u003e\u003c/p\u003e\u003cp\u003ePlasma levels of u-PA were measured using the TECHNOZYM u-PA ELISA Kit (Technoclone) following the manufacturer’s instructions. The assay wells were pre-coated with a monoclonal anti-u-PA antibody. After washing, the plates were incubated with a conjugated polyclonal anti-u-PA antibody for 1 hour at 37°C. Following additional washes, a substrate solution was added and incubated for 20 minutes at room temperature, after which a stop solution was applied. The absorbance was then measured at 450 nm.\u003c/p\u003e\u003cp\u003e\u003cb\u003eEvaluation of plap complex levels\u003c/b\u003e\u003c/p\u003e\u003cp\u003e Plasma levels of plasmin–α2-antiplasmin (plap) complexes were measured using the DRG PAP ELISA RUO Kit (DRG Instruments, Marburg, Germany) following the manufacturer’s guidelines.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAssessment of complement levels\u003c/b\u003e\u003c/p\u003e\u003cp\u003eComplement analyte measurements of C3a, C4a, C5a, soluble C5b-9 (sC5b-9), Ba, Bb, factor H and factor I were performed using a Quansys Q-View Imager LS system with Quidel MicroVue complement multiplex kit, according to the manufacturer’s instructions. Increases in C3a, C4a, C5a, soluble C5b-9 (sC5b-9), Ba, Bb represent complement activation, whereas factors H and I are inhibitors [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eViscoelastic testing\u003c/b\u003e\u003c/p\u003e\u003cp\u003eViscoelastic whole blood analysis was conducted using Rotational Thromboelastometry (ROTEM®, Werfen France). Four different assays were performed to evaluate coagulation both before (pre-lysis) and during (at 6 hours) USAT treatment. The EXTEM assay activates the extrinsic coagulation pathway via tissue factor. The INTEM assay triggers the intrinsic pathway using negatively charged surfaces such as kaolin or ellagic acid. The FIBTEM assay isolates fibrinogen function by adding cytochalasin, which inhibits platelet microfilaments, thereby removing the influence of platelet-driven clot retraction. Since all patients received heparin therapy, the HEPTEM assay was also included; it incorporates heparinase to neutralize heparin’s effects. The parameters measured included clotting time (CT, seconds), clot formation time (CFT, seconds), α-angle (degrees) reflecting fibrin polymerization rate, clot strength at 10 minutes (A10, mm), maximum clot firmness (MCF, mm), and maximum clot lysis (ML, %) as a marker of fibrinolysis [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003ePatient characteristics—including medical history, symptoms, vital signs, catheterization data, and discharge details from the initial hospitalization—were summarized using counts with percentages, means with standard deviations, or medians with interquartile ranges (IQR). Correlation analyses were conducted using Spearman’s correlation coefficient, adjusted for rt-PA dosage. The adjusted Spearman rank correlations were calculated following the method described by Liu et al [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eComplement components were evaluated for their predictive value using generalized linear models to examine their relationship with the change in mean pulmonary artery pressure (PAPm) between catheter placement and removal. These models were adjusted for the rt-PA dose administered during USAT. The same modeling approach was used to investigate the association between these hemostatic markers and the reduction in the right-to-left ventricular (RV/LV) ratio post-lysis compared to the initial RV/LV ratio measured on the CTA scan at PE diagnosis. To obtain robust standard errors and account for possible deviations from normality, bootstrapping with 1,000 replications was employed for variance-covariance matrix estimation. This resampling technique repeatedly samples with replacement from the original data and recalculates model estimates for each iteration, improving the accuracy of standard error and confidence interval estimates.\u003c/p\u003e\u003cp\u003eAll statistical analyses were conducted using Stata 17 (StataCorp LLC, College Station, TX, USA). A p-value below 0.05 was considered statistically significant. Figures were created using GraphPad Prism 10.1.2 (GraphPad Software, La Jolla, CA, USA).\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cb\u003eBaseline and procedural characteristics\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe baseline characteristics of the study cohort are displayed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The vast majority of patients (89%) presented with an intermediate-high risk PE according to the ESC classification [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], while the remaining 11% of individuals were classified as high-risk PE patients. Sixty percent of the patients were male. Among the identified risk factors for venous thromboembolism, 11% of cases were associated with a prior COVID-19 infection, 20% of patients had diabetes, and another 20% were active smokers. Approximately one-third had a history of PE or deep vein thrombosis. Additionally, one patient each (3%) was bedridden, using hormonal contraceptives, had recently undergone major surgery, or had an active malignancy. Details of the procedure, including right heart catheterization measurements and rt-PA dosing and infusion duration, are provided in \u003cb\u003eSupplementary Appendix\u003c/b\u003e Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Notably, no reperfusion therapies other than ultrasound-assisted thrombolysis (USAT) and anticoagulation\u0026mdash;such as interventional or surgical embolectomy\u0026mdash;were employed in this cohort. USAT was administered using rt-PA as the sole thrombolytic agent. In one case, a 5 mg bolus of rt-PA per catheter was given prior to continuous infusion. The total rt-PA dose was 20 mg in 80% of patients, 15 mg in 11%, and 10 mg in 9%.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eBaseline characteristics\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003en\u0026thinsp;=\u0026thinsp;35\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePE classification of risk (ESC)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- low\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- intermediate-low\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- intermediate-high\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e31 (89%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- high\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (11%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e64.3\u0026thinsp;\u0026plusmn;\u0026thinsp;11.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSex (Male)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e21 (60%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHeight (cm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e171.5\u0026thinsp;\u0026plusmn;\u0026thinsp;10.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWeight (kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e85.6\u0026thinsp;\u0026plusmn;\u0026thinsp;17.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBody mass index (kg/m\u0026sup2;)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e29.1 \u0026plusmn; 5.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCOVID associated\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (11%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDiabetes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (20%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDiabetes treatment\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003en = 7,\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- diet\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (14%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- oral treatment\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5 (71%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- insulin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (14%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGlomerular filtration rate (mL/min(1.73m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e74.8\u0026thinsp;\u0026plusmn;\u0026thinsp;16.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- eGFR\u0026thinsp;\u0026gt;\u0026thinsp;60 mL/min(1.73m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003en\u0026thinsp;=\u0026thinsp;28 (80%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- eGFR 30\u0026ndash;60 mL/min(1.73m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003en\u0026thinsp;=\u0026thinsp;7 (20%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- eGFR\u0026thinsp;\u0026lt;\u0026thinsp;30 mL/min(1.73m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003en\u0026thinsp;=\u0026thinsp;0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDyslipidemia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5 (14%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCOPD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (3%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOther lung disease\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3 (9%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTobacco consumption\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003en\u0026thinsp;=\u0026thinsp;30,\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- active\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6 (20%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- ex-smoker\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e9 (30%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- never-smoker\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e15 (50%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAlcohol abuse\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2 (6%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLiver disease\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMajor surgery within 4 weeks\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (3%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBedridden\u0026thinsp;\u0026gt;\u0026thinsp;3 days\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (3%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCoronary artery disease\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrevious percutaneous intervention\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrevious stroke\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrevious Hx of myocardial infarction\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrevious Hx of permanent PM / ICD / CRT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrevious PE\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (11%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrevious deep vein thrombosis\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 (20%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrevious cardiac surgery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCurrent bleeding\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrevious bleeding\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBleeding diathesis (known)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCurrent pregnancy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRecent delivery (\u0026lt;\u0026thinsp;90 days)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eContraception\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (3%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrevious cancer\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2 (6%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eActive malignancy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (3%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e- Active metastatic cancer\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (3%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eUSAT results in reduced complement activation fragment levels\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe complement activation fragments C3a and Ba displayed a significant reduction during USAT compared with baseline, with a concomitant small but significant reduction in complement control protein factors I and H (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Other parameters of the complement system were not affected by the treatment (\u003cb\u003eSupplementary Appendix Table\u0026nbsp;2.\u003c/b\u003e)\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eFibrinolytic markers correlate with complement components at t\u0026thinsp;=\u0026thinsp;6h (Spearman correlation adjusted for rt-PA dose, n\u0026thinsp;=\u0026thinsp;35; only significant correlations displayed)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eparameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003erho\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ep-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eα2-antiplasmin vs Bb\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.5873096\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e\u0026lt;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eplap complex vs Ba\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.4800978\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.004\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eα2-antiplasmin vs Ba\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.4820493\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.006\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eplap complex vs Bb\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.4590815\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.006\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eplap complex vs C5a\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.4299794\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.011\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eα2-antiplasmin vs factor I\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.3864462\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.032\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eα2-antiplasmin vs factor H\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.3854377\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.032\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eplap complex vs factor H\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.3651771\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.043\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eplap complex vs sC5b-9\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-0.3399542\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0.049\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eFibrinolytic markers correlate with complement components during USAT\u003c/b\u003e\u003c/p\u003e\u003cp\u003eWhen evaluating the correlative interaction of fibrinolytic markers and complement components, we found a positive correlation of the plap complex with factor H. Conversely, we observed a negative correlation of the plap complex with both Ba and Bb. A negative correlation of the plap complex was also evident with C5a and sC5b-9. The potent plasmin-inhibitor α2-antiplasmin displayed a positive correlation with Ba and Bb, factor I and factor H (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cb\u003eThe anaphylatoxin C5a negatively predicts treatment responsiveness to USAT\u003c/b\u003e\u003c/p\u003e\u003cp\u003eComplement components were assessed during lysis (t\u0026thinsp;=\u0026thinsp;6h) for their capacity to predict treatment responsiveness (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The anaphylatoxin C5a positively predicted post-thrombolysis PAPm controlling for pre-lysis PAPm and rt-PA dose, hence acting as a negative predictor for treatment responsiveness. Similarly, C5a evaluated before start of USAT also negatively predicted treatment responsiveness represented by PAPm reduction (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). With respect to a reduction in the RV/LV ratio, none of the assessed complement components predicted the reduction in response to USAT if assessed during lysis (\u003cb\u003eSupplementary Appendix\u003c/b\u003e Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In turn, Ba evaluated before treatment start acted as a negative predictor for a reduction in RV/LV ratio after USAT (\u003cb\u003eSupplementary Appendix\u003c/b\u003e Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComplement components assessed during lysis (t\u0026thinsp;=\u0026thinsp;6h) predict post-thrombolysis PAPm controlling for pre-lysis PAPm and rt-PA dose (n\u0026thinsp;=\u0026thinsp;35)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eparameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ebootstrap coefficient (95% CI)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ep-value\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"1\" nameend=\"c4\" namest=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC5a\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.55307 [0.11900 to 0.98713] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.013\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"1\" nameend=\"c4\" namest=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBb\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.87482 [-1.80532 to 17.55495] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c4\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC4a\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.00587 [-0.01544 to 0.00369] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c4\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.01011 [-0.00690 to 0.02712] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c4\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003esC5b-9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.00603 [-0.01035 to 0.02241] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c4\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003efactor H\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.00971 [-0.02526 to 0.04467] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c4\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC3a\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.01423 [-0.07767 to 0.04920] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c4\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003efactor I\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.00007 [-0.00029 to 0.00043] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c4\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComplement components assessed before treatment start predict post-thrombolysis PAPm controlling for pre-lysis PAPm and rt-PA dose (n\u0026thinsp;=\u0026thinsp;35)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eparameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ebootstrap coefficient (95% CI)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003ep-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC5a\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.57096 [0.13231 to 1.00960] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0.011\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBb\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.03402 [-1.58194 to 15.64999] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0.12\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003esC5b-9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.00798 [-0.00339 to 0.01935] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0.17\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003efactor I\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.00019 [-0.00060 to 0.00022] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.00499 [-0.00825 to 0.01824] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0.46\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC4a\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.00285 [-0.01058 to 0.00487] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0.47\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC3a\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.01173 [-0.05653 to 0.03307] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0.61\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003efactor H\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.00458 [-0.04227 to 0.05144] (n\u0026thinsp;=\u0026thinsp;29)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0.85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eWe have previously demonstrated a significant variability in the treatment efficacy of USAT in acute PE [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In a subsequent subgroup analysis, we showed that the endogenous fibrinolytic capacity assessed during ongoing thrombolysis, as well as the fibrinolytic potential evaluated before treatment initiation, predicted the individual treatment responsiveness as indicated by a reduction in PAPm [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] An unbalanced expression of complement components, regulators and receptors has previously been reported in patients with symptomatic PE [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Moreover, the extent of complement activation has been associated with RV dysfunction and PE severity [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn this investigation, we aimed to evaluate changes in circulating levels of various complement components in the setting of acute PE and subsequent USAT, given the known interaction between plasmin and the complement system in various clinical scenarios [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Speculating that the supraphysiological plasmin activity achieved with thrombolytic therapy might also enhance complement activation, we obtained the following results:\u003c/p\u003e\u003cp\u003eRather than an increase, USAT resulted in a reduction of two complement activation fragments (C3a, Ba) and a small but significant reduction of complement control proteins (factors I and H). When evaluating the correlative interaction of fibrinolytic markers and complement components, we found a positive correlation of the plap complex, representing plasmin generation, with factor H. Conversely, we observed a negative correlation of the plap complex with both Ba and Bb. Importantly, a negative correlation of the plap complex was also evident with C5a and sC5b-9. The potent plasmin-inhibitor α2-antiplasmin displayed a positive correlation with Ba, Bb, factor I and factor H. Levels of the anaphylatoxin C5a, evaluated either before or during USAT, negatively predicted treatment responsiveness, represented by a reduction in PAPm (i.e. positively predicted post-thrombolysis PAPm controlling for pre-lysis PAPm and rt-PA dose).\u003c/p\u003e\u003cp\u003eCuriously, the plap complex, a marker of plasmin generation, correlated negatively with C5a, despite plasmin being known as a potent activator of C5 [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. This suggests that the therapeutic effects of plasmin with a resulting reduction in RV strain [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] and concomitant reduced C5 activation stimulus may exceed its C5-activating properties in the setting of USAT for PE. sC5b-9, the final product of the complement cascade, also correlated negatively with the plap complex. In addition, circulating levels of various complement components and their regulators are diminished as a result of USAT. Thus, while supraphysiologic plasmin generation, as occurring during thrombolytic therapy, may promote complement activation and other non-fibrinolytic effects of plasmin, complement activation as a direct consequence of PE is attenuated. This is most likely due to the resolution of clot burden and ischemia, as well as the reduction of RV strain, resulting in less overall pathophysiologic stress to the patient.\u003c/p\u003e\u003cp\u003eConsistent with this observation, C5a acted as a negative predictor of treatment response, indicating that increased treatment response actually results in decreased complement system activity and a reduction in circulating complement components. Hence, C5a appears to be a marker of treatment response, rather than of plasmin generation per se. In contrast, C3a and sC5b-9 did not predict treatment response, which may be related to differences in abundance, regulatory control, and half-life [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Levels of C3 are much higher than those of C5, hence baseline and active levels of C3a are higher than C5a. The half-lives of C3a and C5a are only a few minutes, while the half-life of sC5b-9 is several hours. Hence, sC5b-9, while reflecting C5 cleavage, is more of a global activation marker, rather than a real-time measurement of changes in the complement cascade in that exact moment.\u003c/p\u003e\u003cp\u003eThese findings are further corroborated by the observed negative correlation of the plap complex with Ba and Bb, and its positive correlation with factors I and H. In contrast, a positive correlation can be observed for Ba and Bb with α2-antiplasmin, the central plasmin inhibitor that is consumed as a result of plasmin generation and plap complex formation [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Cleavage of factor B occurs during the activation of the alternative pathway, resulting in the fragments Ba and Bb. Bb then forms a part of the C3 convertase. In turn, factors I and H inhibit the deposition of C3b on host cells, thereby regulating the alternative pathway [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. The observed reduction of the control proteins factors I and H in parallel with C3a suggests, that the resolving process of PE triggers or aids factors I and H in their capacity to downregulate complement. The exact mechanism behind this curious observation remains to be elucidated.\u003c/p\u003e\u003cp\u003eOf particular interest in this context is also the role of the alternative pathway. Ba and Bb correlated with the plap complex and α2-antiplasmin, and Ba was reduced during USAT as well. The alternative pathway is constantly active, so loss of regulation may occur in the critically ill PE patient, and this regulatory ability may be restored when PE is dissolved by plasmin, leading to reduced Ba. Similarly, ischemia is thought to trigger alternative pathway activation, as demonstrated by Ganter et al [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Likewise, resolution of ischemia may resolve this alternative pathway activation through restoration of regulatory pathway homeostasis.\u003c/p\u003e\u003cp\u003eWe have previously suggested that patients may benefit from a dose adjustment of the thrombolytic agent based on the individual predicted treatment responsiveness [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].The ideal thrombolytic dose may allow an optimal compromise of achieving treatment efficacy and clearance of the inflammatory trigger, while at the same time limiting the known pro-inflammatory effects of plasmin [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] to a minimum. An individualized treatment approach is therefore the goal of our ongoing investigation, and a validation study to establish the optimal markers to predict individual treatment responsiveness is currently underway.\u003c/p\u003e\u003cp\u003eWith respect to the capacity of circulating C5a, assessed prior to USAT initiation, to predict treatment response, a mechanistic involvement can be speculated. However, whether modulation of the complement system itself could be beneficial in acute PE, as previously suggested [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], remains elusive and requires further investigation.\u003c/p\u003e\u003cp\u003eIn summary, in the setting of acute PE and reperfusion therapy with USAT, there appears to be a competing effect between plasmin-mediated activation of inflammation and a reduction of the inflammatory trigger by resolution of pulmonary vascular obstruction and ischemia, with consequent reduction of PAPm and RV strain. According to our findings, complement activation in PE is downregulated in response to USAT, an effect that exceeds the complement-activating properties of plasmin.\u003c/p\u003e\u003cp\u003e\u003cb\u003eLimitations\u003c/b\u003e\u003c/p\u003e\u003cp\u003eSeveral limitations of this study should be noted. First, this investigation was derived from a pilot study and may be underpowered to draw definitive conclusions. Second, this was a single-center study, and our results require external validation in other centers/populations to confirm that our findings are broadly applicable to patients with acute PE. Third, a control group of PE patients treated with anticoagulation alone could not be provided, which may inform us about levels of fibrinolytic proteases/inhibitors and complement components in PE patients not receiving USAT. Finally, the assays and parameters used are not currently approved for clinical use or standardized to guide treatment decisions in this indication.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eCTA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;computed tomography angiography scan\u003c/p\u003e\n\u003cp\u003eESC \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;European Society of Cardiology\u003c/p\u003e\n\u003cp\u003eLV \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;right ventricle\u003c/p\u003e\n\u003cp\u003ePAPm\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;mean pulmonary arterial pressure\u003c/p\u003e\n\u003cp\u003ePE \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;pulmonary embolism\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePERT \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;pulmonary embolism response team\u003c/p\u003e\n\u003cp\u003eplap \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;plasmin-antiplasmin\u003c/p\u003e\n\u003cp\u003eREDCap \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Research Electronic Data Capture\u003c/p\u003e\n\u003cp\u003ert-PA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;recombinant tissue-type plasminogen activator\u003c/p\u003e\n\u003cp\u003eRV \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;right ventricle\u003c/p\u003e\n\u003cp\u003esC5b-9\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;soluble C5b-9\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eu-PA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;urokinase-type plasminogen activator\u003c/p\u003e\n\u003cp\u003eUSAT \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Ultrasound-assisted catheter-directed thrombolysis\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study protocol was approved by the local ethics committee and all patients provided written informed consent for study participation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eS. Stortecky reports research grants to the institution from Edwards Lifesciences, Medtronic, Abbott, Boston Scientific and has a consulting contract with Inari Medical outside the submitted work.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNone of the authors have any competing interest to declare with respect to this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eERASE PE is sponsored by intramural study grants provided by the Swiss Cardiovascular Center Bern. Laboratory analyses were funded through a project grant obtained from the Bern Center of Precision Medicine, Department of Biomedical Research, University of Bern.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDFD, CDB, and SS designed the project and prepared the protocols. CDB, ERM, HH, CBK and RLM developed and performed the laboratory assays. DFD and SS recruited patients and SS collected the clinical data. KC and DH performed the statistical analyses. DFD and CDB prepared the manuscript. All authors reviewed the manuscript and provided expert evaluation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eWendelboe, A.M. and G.E. 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Stortecky, \u003cem\u003eInterventional Reperfusion Strategies for Acute Pulmonary Embolism.\u003c/em\u003e Praxis (Bern 1994), 2021. \u003cstrong\u003e110\u003c/strong\u003e(13): p. 743-751.\u003c/li\u003e\n\u003cli\u003eDraxler, D.F., et al., \u003cem\u003eClinical Outcomes in Patients With Acute Pulmonary Embolism Undergoing Ultrasound-Assisted Catheter-Directed Thrombolysis.\u003c/em\u003e J Am Heart Assoc, 2025. \u003cstrong\u003e14\u003c/strong\u003e(9): p. e035916.\u003c/li\u003e\n\u003cli\u003eDraxler, D.F., et al., \u003cem\u003eThe individual fibrinolytic capacity predicts the efficacy of ultrasound-assisted catheter-directed thrombolysis in patients with acute pulmonary embolism.\u003c/em\u003e J Thromb Haemost, 2025. \u003cstrong\u003e23\u003c/strong\u003e(4): p. 1416-1427.\u003c/li\u003e\n\u003cli\u003eDraxler, D.F., M. Sashindranath, and R.L. Medcalf, \u003cem\u003ePlasmin: A Modulator of Immune Function.\u003c/em\u003e Semin Thromb Hemost, 2017. \u003cstrong\u003e43\u003c/strong\u003e(2): p. 143-153.\u003c/li\u003e\n\u003cli\u003eKeragala, C.B., et al., \u003cem\u003eHaemostasis and innate immunity - a complementary relationship: A review of the intricate relationship between coagulation and complement pathways.\u003c/em\u003e Br J Haematol, 2018. \u003cstrong\u003e180\u003c/strong\u003e(6): p. 782-798.\u003c/li\u003e\n\u003cli\u003eAmara, U., et al., \u003cem\u003eMolecular Intercommunication between the Complement and Coagulation Systems.\u003c/em\u003e The Journal of Immunology, 2010. \u003cstrong\u003e185\u003c/strong\u003e(9): p. 5628-5636.\u003c/li\u003e\n\u003cli\u003eBarrett, C.D., et al., \u003cem\u003eTranexamic acid mediates proinflammatory and anti-inflammatory signaling via complement C5a regulation in a plasminogen activator-dependent manner.\u003c/em\u003e J Trauma Acute Care Surg, 2019. \u003cstrong\u003e86\u003c/strong\u003e(1): p. 101-107.\u003c/li\u003e\n\u003cli\u003eHarris, P.A., et al., \u003cem\u003eResearch electronic data capture (REDCap)--a metadata-driven methodology and workflow process for providing translational research informatics support.\u003c/em\u003e J Biomed Inform, 2009. \u003cstrong\u003e42\u003c/strong\u003e(2): p. 377-81.\u003c/li\u003e\n\u003cli\u003eHarris, P.A., et al., \u003cem\u003eThe REDCap consortium: Building an international community of software platform partners.\u003c/em\u003e J Biomed Inform, 2019. \u003cstrong\u003e95\u003c/strong\u003e: p. 103208.\u003c/li\u003e\n\u003cli\u003eBarrett, C.D., et al., \u003cem\u003eHyperfibrinolysis is Associated with Complement Activation Following Trauma.\u003c/em\u003e Thromb Haemost, 2025.\u003c/li\u003e\n\u003cli\u003eDrotarova, M., et al., \u003cem\u003eBasic Principles of Rotational Thromboelastometry (ROTEM((R))) and the Role of ROTEM-Guided Fibrinogen Replacement Therapy in the Management of Coagulopathies.\u003c/em\u003e Diagnostics (Basel), 2023. \u003cstrong\u003e13\u003c/strong\u003e(20).\u003c/li\u003e\n\u003cli\u003eLiu, Q., et al., \u003cem\u003eCovariate-adjusted Spearman\u0026apos;s rank correlation with probability-scale residuals.\u003c/em\u003e Biometrics, 2018. \u003cstrong\u003e74\u003c/strong\u003e(2): p. 595-605.\u003c/li\u003e\n\u003cli\u003eLv, W., et al., \u003cem\u003eCharacteristics of the complement system gene expression deficiency in patients with symptomatic pulmonary embolism.\u003c/em\u003e Thromb Res, 2013. \u003cstrong\u003e132\u003c/strong\u003e(1): p. e54-7.\u003c/li\u003e\n\u003cli\u003eRostoff, P., et al., \u003cem\u003eComplement activation is associated with right ventricular dysfunction and the severity of pulmonary embolism: links with prothrombotic state.\u003c/em\u003e J Thorac Dis, 2024. \u003cstrong\u003e16\u003c/strong\u003e(5): p. 3181-3191.\u003c/li\u003e\n\u003cli\u003eAmara, U., et al., \u003cem\u003eMolecular intercommunication between the complement and coagulation systems.\u003c/em\u003e J Immunol, 2010. \u003cstrong\u003e185\u003c/strong\u003e(9): p. 5628-36.\u003c/li\u003e\n\u003cli\u003eFoley, J.H., B.L. Walton, and M.M. Aleman, \u003cem\u003eComplement activation in arterial and venous thrombosis is mediated by plasmin.\u003c/em\u003e EBioMedicine, 2016. \u003cstrong\u003e5\u003c/strong\u003e: p. 175-182.\u003c/li\u003e\n\u003cli\u003eAyano, M. and T. Horiuchi, \u003cem\u003eComplement as a Biomarker for Systemic Lupus Erythematosus.\u003c/em\u003e Biomolecules, 2023. \u003cstrong\u003e13\u003c/strong\u003e(2).\u003c/li\u003e\n\u003cli\u003eMorgan, B.P., et al., \u003cem\u003eComplement: central to innate immunity and bridging to adaptive responses.\u003c/em\u003e Immunol Lett, 2005. \u003cstrong\u003e97\u003c/strong\u003e(2): p. 171-9.\u003c/li\u003e\n\u003cli\u003eGanter, M.T., et al., \u003cem\u003eRole of the alternative pathway in the early complement activation following major trauma.\u003c/em\u003e Shock, 2007. \u003cstrong\u003e28\u003c/strong\u003e(1): p. 29-34.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"thrombosis-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"thrj","sideBox":"Learn more about [Thrombosis Journal](http://thrombosisjournal.biomedcentral.com/)","snPcode":"12959","submissionUrl":"https://submission.nature.com/new-submission/12959/3","title":"Thrombosis Journal","twitterHandle":"@Thrombosis_J","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Pulmonary embolism, catheter-directed thrombolysis, fibrinolysis, fibrinolytic potential, fibrinolytic capacity, inflammation, complement","lastPublishedDoi":"10.21203/rs.3.rs-7180620/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7180620/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eUltrasound-assisted catheter-directed thrombolysis (USAT) with recombinant tissue-type plasminogen activator (rt-PA) is widely used as a reperfusion approach for acute pulmonary embolism (PE). The fibrinolytic effector protease plasmin is known to be a potent activator of the complement system. The aim of this study was to better characterize the extent of complement activation during USAT, and its relationship with the fibrinolytic system.\u003c/p\u003e\u003cp\u003eIn this single-center cohort study of USAT for PE, pulmonary-arterial hemodynamic measurements were performed, and plasma samples obtained from 35 patients before treatment start and at 6 hours (during infusion of rt-PA). Hemostatic properties were evaluated with thromboelastometry and assessment of fibrinolytic markers. In addition, levels of the complement components C3a, C4a, C5a, soluble C5b-9 (sC5b-9), Ba, Bb, factor H and factor I at these time points were determined.\u003c/p\u003e\u003cp\u003eSeveral complement components, including the anaphylatoxin C3a, showed a reduction during USAT. We found a positive correlation of the plasmin-antiplasmin complex (plap complex) with factor H, yet a negative correlation with both Ba and Bb, C5a and sC5b-9. The potent plasmin-inhibitor, α2-antiplasmin, displayed a positive correlation with Ba and Bb, factor I and factor H. In addition, the anaphylatoxin C5a negatively, and Ba positively predicted treatment responsiveness to USAT.\u003c/p\u003e\u003cp\u003eIn conclusion, in the setting of acute PE and reperfusion therapy with USAT, there appears to be a competing effect between plasmin-mediated complement activation and a reduction of the inflammatory trigger by resolution of obstruction and ischemia. Complement activation in PE is downregulated during USAT, an effect exceeding the complement-activating properties of plasmin.\u003c/p\u003e","manuscriptTitle":"The interaction of fibrinolysis and the complement system in patients with acute pulmonary embolism, treated with ultrasound-assisted catheter-directed thrombolysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-15 06:32:30","doi":"10.21203/rs.3.rs-7180620/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-11T23:07:40+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-23T14:47:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-04T09:07:09+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-27T05:10:10+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"235145725632805838057537482997212383086","date":"2025-09-24T08:35:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"8466280646960267169898725777601188296","date":"2025-09-22T12:38:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"309603468240165450893101283779456967894","date":"2025-09-09T23:35:12+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-08T06:30:53+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-22T04:54:56+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-22T04:52:38+00:00","index":"","fulltext":""},{"type":"submitted","content":"Thrombosis Journal","date":"2025-07-21T20:00:03+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"thrombosis-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"thrj","sideBox":"Learn more about [Thrombosis Journal](http://thrombosisjournal.biomedcentral.com/)","snPcode":"12959","submissionUrl":"https://submission.nature.com/new-submission/12959/3","title":"Thrombosis Journal","twitterHandle":"@Thrombosis_J","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c2a83df7-b1e7-4cf7-9bbc-72c5176b0169","owner":[],"postedDate":"September 15th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-02-02T16:00:31+00:00","versionOfRecord":{"articleIdentity":"rs-7180620","link":"https://doi.org/10.1186/s12959-026-00830-3","journal":{"identity":"thrombosis-journal","isVorOnly":false,"title":"Thrombosis Journal"},"publishedOn":"2026-01-29 15:58:20","publishedOnDateReadable":"January 29th, 2026"},"versionCreatedAt":"2025-09-15 06:32:30","video":"","vorDoi":"10.1186/s12959-026-00830-3","vorDoiUrl":"https://doi.org/10.1186/s12959-026-00830-3","workflowStages":[]},"version":"v1","identity":"rs-7180620","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7180620","identity":"rs-7180620","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}