Predictors of Transmural Lesion in High Power Short Duration Ablation of Atrial Fibrillation Guided by Local Impedance

Predictors of Transmural Lesion in High Power Short Duration Ablation of Atrial Fibrillation Guided by Local Impedance | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Predictors of Transmural Lesion in High Power Short Duration Ablation of Atrial Fibrillation Guided by Local Impedance Yoon Kee Siow, Shih-Lin Chang, Fa-Po Chung, Yenn-Jiang Lin, Li-Wei Lo, and 17 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5113011/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: The impact of local impedance (LI) drop in high power short duration (HPSD) for atrial fibrillation (AF) remains unclear. Objective : This study aimed to assess the parameters predicting transmural lesions. Method: Thirty patients (76.7% male, mean 59.6±10.0 years old) with AF who underwent radiofrequency ablation were enrolled. Ablation lesions of pulmonary vein isolation (PVI) were created by HPSD (50W, ≤15s and LI drop ≤30%). Successful and non-successful lesions were defined by electrogram criteria. Absolute and percentage LI drop of ablation lesions were recorded. Results: Of 210 ablation lesions included, 67.6% (n=142) were successful lesions. The mean percentage and absolute LI drop were higher in successful than in non-successful lesions (19.7±4.6% vs. 15.1±3.1%, p<0.001; 33.8±9.8Ω vs. 24.0±5.7Ω, p<0.001). To create successful lesions, higher absolute LI drop was required in the right than in the left PV antrum (35.5±10.0Ω vs. 31.8±9.2Ω, p=0.032), while higher percentage and absolute LI drop were required in the anterior than in the posterior PV antrum (20.8±4.9% vs. 18.3±3.8%, p=0.002; 35.6±10.2Ω vs. 31.4±8.6Ω, p=0.008). Among 142 successful lesions, the higher initial LI group (>190 Ω) had a higher mean percentage and absolute LI drop, and shorter mean duration of ablation compared with lower initial LI groups (<150Ω, 150Ω-170Ω, 170Ω-190Ω). The cut-off values of percentage and absolute LI drop were 16.2% and 26.5Ω, respectively, to predict the successful lesions. Conclusion: In successful lesion of PVI, initial LI was associated with LI drop and duration of ablation. The LI could predict transmural lesions and guide HPSD ablation. atrial fibrillation ablation initial local impedance impedance drop Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Highlights In predicting transmural lesions in atrial fibrillation ablation, initial local impedance (LI) was directly proportional to LI drop and inversely proportional to duration. A strong correlation between percentage and absolute LI drop and either parameter predicted the successful and transmural lesions. 1. Introduction Catheter ablation (CA) is a safe and effective treatment in drug-refractory atrial fibrillation (AF). 1 The combination of different parameters during ablation, such as contact force, duration, power, or current, may provide radiofrequency CA (RFCA) guidance and improve long-term outcomes. 2 – 5 To achieve acute and long-term success of CA, transmurality of ablation lesions is considered the cornerstone in AF ablation. 6 , 7 The local electrogram (EGM) reflects the conduction gap and transmural lesions, 6 , 8 and this may be served as an indicator to define successful and transmural ablation lesions in a point-by-point manner. However, no single ablation dosage fits all myocardia. In real-world settings, myocardial tissues of the left atrium may interweave with healthy and scarred myocardial tissue. In such circumstances, local impedance (LI) offers real-time information on tissue characteristics before and during ablation. 9 On the other hand, RFCA with high power short duration (HPSD) has been proven to be safe, fast, and effective in creating durable lesions of AF ablation. 10 However, the optimal parameters of LI for HPSD strategy using the ablation catheter with the contact force and LI remain unclear. The current study aimed to determine the optimal parameters and strategies for creating transmural lesions in pulmonary vein isolation (PVI) with the HPSD strategy. 2. Method 2.1 Patient Selection This single-center, retrospective study was conducted at Taipei Veterans General Hospital, Taiwan. The study duration started from 1st March 2022 to 31st October 2022. A total of 30 consecutive patients diagnosed with paroxysmal or persistent AF receiving HPSD 50W AF ablation for PVI with Rhythmia HDx system (Boston Scientific, Marlborough, MA, USA) were retrospectively recruited. Intellamap Orion high-resolution mapping catheters and Intellanav Stablepoint irrigated ablation catheters (Boston Scientific, Marlborough, MA, USA) were used for all patients in this study. The catheter was equipped with distal tips to measure the LI of myocardial tissue. It provides LI data, offering comprehensive tissue characteristics in real-time. 11 AF was defined as patients’ electrocardiogram (ECG) or Holter monitoring showing irregular tracings without any repetitive or discernible P wave. Paroxysmal AF was defined as an AF episode that was terminated spontaneously or after relevant intervention within seven days, while persistent AF was defined as an AF episode that lasted beyond seven days. 1 Baseline characteristics, comorbidities, medications and echocardiographic parameters were retrieved from hospital-based electronic medical records. 2.2 Ablation Procedure The details of the procedure and protocol were described in our previous publications. 12 – 15 Anti-arrhythmic medications (except amiodarone) were withheld in all patients for more than five half-lives before the procedure. The procedures were conducted either under light sedation or general anesthesia. A 6F decapolar catheter (St. Jude Medical, Inc., St. Paul MN, USA) was placed into the coronary sinus via a right internal jugular venous access. Two transseptal atrial punctures were then performed under fluoroscopic guidance or transesophageal echocardiography. 8.5F SL-0 (Abbott Laboratories, Abbott Park, IL, USA) sheaths were inserted into the left atrium (LA) via right femoral venous accesses. Intellamap Orion high-resolution mapping catheter (Boston Scientific, Marlborough, MA, USA) was then positioned into the LA to create electroanatomical geometry. All patients then received PVI at bilateral pulmonary vein (PV) antra using an Intellanav Stablepoint irrigated ablation catheter. HPSD radiofrequency energy of 50W, with a maximum duration of less than 15 seconds and LI drop of 30% were applied for each lesion. Tests for entrance or exit block of the PV by pacing either from the coronary sinus or the PV, respectively, determining absence of electrical activities within the PV, or identifying PV dissociation were done after PVI. After PVI, the inducibility of AF was performed. The protocol used for AF inducibility was published in our previous study. 16 Non-PV foci were ablated if these were identified during inducibility testing. When atrial flutter or focal atrial tachycardia was induced, additional focal or linear ablation was performed after studying the mechanism of the arrhythmia. Cavotricuspid isthmus ablation was performed on all patients. Activated clotting time (ACT) was maintained at ≥ 300 seconds during the procedure. 2.3 Successful, non-successful and gap lesions Bipolar EGMs of ablation lesions for PVI were analyzed retrospectively with a scale of 32x and a sweep speed of 100 mm/s using the LabSystem Pro EP Recording System (Boston Scientific, Marlborough, MA, USA). The amplitude of pre-ablation lesions of ≥ 0.3mV were included for analysis. A successful lesion was defined as a reduction of > 75% of the R wave in the QRS complex, or a complete disappearance of R’ or RSR’ patterns of the bipolar EGM 6 , 17 and post-ablation showed < 0.3mV during voltage mapping. A lesion which did not meet these criteria was considered a non-successful lesion. The pre-ablation lesions that measured < 0.3mV were not recruited into the analysis pool as the signals were very small. (Fig. 1 ) The parameters of gap lesions were obtained in patients who did not achieve first-pass isolation, without applying EGM criteria. 2.4 Local Impedance of Ablation Lesion Data from the Rhythmia HDx mapping system were retrospectively retrieved and labeled. The ablation lesions that met the bipolar EGM criteria were recruited into the analysis. Duration, force of each ablation lesion, initial and final LI (absolute and percentage drop) from the Rhythmia HDx mapping system were retrieved. Ablation lesions that contained the following were excluded from the analysis: lesions delivered in < 5 seconds duration, lesions with 300Ω, and incomplete lesion data. 2.5 Follow-up and Detection of Arrhythmia Recurrence After the procedure, the patients were discharged and scheduled in the outpatient clinic for regular follow-up at two weeks and every 1–3 months after the CA. Routine ECG was obtained at each outpatient follow-up, and a 7-day event recording was performed in the third month after the procedure. When the patients experienced any symptoms suggestive of arrhythmia, either a 24-hour Holter monitoring or cardiac event recording was conducted to ascertain the cause of the symptoms. AF recurrence was defined as documented AF or atrial tachycardia lasting for more than 30 seconds after the blanking period. 2.6 Data Analysis Demographic details of patients were presented in tables. All statistical tests were performed using IBM SPSS Statistics software version 26 (SPSS Inc, Chicago, IL, USA). Continuous variables were compared using the Student-t test and one-way ANOVA if the data distribution were normal, and the Mann-Whitney test and Kruskal-Wallis test if the data distribution were not normal. The receiver operating characteristic (ROC) curves were used to determine the area under the curve (AUC) of absolute and percentage of LI drop, and their cut-off values of specificity and sensitivity were determined with Youden Index & Index of Union. The correlation between absolute and percentage of LI drop was analyzed using Spearman correlation. 3. Results 3.1 Patient Characteristics A total of 30 consecutive patients were included (76.7% male, mean 59.6 ± 10.0 years old). The mean LVEF was 58.3 ± 7.0%, and the mean LAD was 38.4 ± 6.1mm. Most of these patients (93.3%, n = 28) had paroxysmal AF. Baseline characteristics were summarized in Table 1 . Table 1 Baseline characteristics of the patients (n = 30) Baseline characteristics n (%) Age (mean ± SD) 59.6 ± 10.0 Sex Male 23 (76.7%) Female 7 (23.3%) Comorbidities Diabetes 1 (3.3%) Hypertension 12 (40.0%) Coronary artery disease 8 (26.7%) Ischemic stroke 2 (6.7%) CHA2DS2-VASc score 1.4 ± 1.3 LVEF, % (mean ± SD) 58.3 ± 7.0 LAD, mm (mean ± SD) 38.4 ± 6.1 Types of AF Paroxysmal 28 (93.3%) Persistent 2 (6.7%) Ablation strategy: PVI and CTI 30 (100%) Linear ablation (Posterior wall isolation) 1 (3.33%) Medications: Antiarrhythmic medications Flecainide 10 (33.3%) Propafenone 11 (36.7%) Amiodarone 3 (10.0%) Dronedarone 2 (6.7%) Beta blockers 8 (26.7%) Calcium channel blockers 7 (23.3%) Anticoagulants Edoxaban 7 (23.3%) Rivaroxaban 10 (33.3%) Dabigatran 3 (10.0%) Procedure time (mean ± SD) 195.8 ± 59.7 Fluoroscopy time (mean ± SD) 43.3 ± 28.9 Abbreviation : CTI = cavotricuspid isthmus isolation, LAD = left atrium diameter, LVEF = left ventricular ejection fraction, PVI = pulmonary vein isolation, SD = standard deviation 3.2 Ablation lesions A total of 210 ablation lesions met the bipolar EGM criteria of transmural lesions. Among these lesions, a total of 142 successful lesions (anterior wall: n = 82, 39.0%; posterior wall: n = 60, 28.6%) and 68 non-successful lesions were analyzed (anterior wall: n = 54, 25.7%, posterior wall: n = 14, 6.7%). (Fig. 2 ) The mean initial LI of overall lesions was 166.6 ± 18.4Ω. There was no difference between the initial LI of anterior and posterior lesions (165.3 ± 18.8Ω vs. 169.0 ± 17.7Ω, p = 0.181). However, there was a significantly higher initial LI in the right than the left PV antrum lesions (174.4 ± 16.0Ω vs. 160.7 ± 18.0Ω, p < 0.001). 3.3 Local Impedance Drop in Successful and Non-Successful Lesions In the overall lesions, the mean LI drop in percentage was higher in successful lesions than in non-successful lesions (19.7 ± 4.6% vs. 15.1 ± 3.1%, p < 0.001). The mean absolute LI drop of overall lesions was also significantly higher in successful lesions compared to non-successful lesions (33.8 ± 9.8Ω vs. 24.0 ± 5.7Ω, p < 0.001). The mean percentage and absolute LI drop of successful lesions were higher than in non-successful lesions in different segments (Table 2 ). Table 2 Comparison of percentage and absolute local impedance drop in successful and non-successful lesions. Parameters Successful lesions Non-successful lesions p value Overall lesions - %LI drop † , % -19.7 ± 4.6 (-18.9) -15.1 ± 3.1 (-15.7) < 0.001 Overall lesions - Absolute LI drop † , Ω -33.8 ± 9.8 (-32.0) -24.0 ± 5.7 (-24.0) < 0.001 Anterior - %LI drop † , % -20.8 ± 4.9 (-19.7) -14.9 ± 3.3 (-15.3) < 0.001 Anterior - Absolute LI drop † , Ω -35.6 ± 10.2 (-34.5) -23.6 ± 5.9 (-24.0) < 0.001 Posterior - %LI drop † , % -18.3 ± 3.8 (-17.5) -15.8 ± 2.4 (-16.1) 0.04 Posterior - Absolute LI drop † , Ω -31.4 ± 8.6 (-29.5) -25.7 ± 4.7 (-26.5) 0.016 Left - %LI drop † , % -19.0 ± 4.2 (-18.2) -14.9 ± 3.2 (-15.5) < 0.001 Left - Absolute LI drop † , Ω -31.8 ± 9.2 (-31.0) -23.1 ± 5.5 (-23.5) < 0.001 Right - %LI drop † , % -20.3 ± 4.9 (-19.3) -16.0 ± 2.8 (-16.0) 0.001 Right - Absolute LI drop † , Ω -35.5 ± 10.0 (-34.0) -27.9 ± 5.1 (-27.0) 0.005 Abbreviation : %LI = local impedance drops in percentage, LI = local impedance Note : Mann-Whitney test, p < 0.05 indicated statistically significant, p < 0.001 indicated highly significant, † mean ± SD (median) 3.4 Impact of Initial Local Impedance in Successful Lesions A higher absolute LI drop was required for creating successful lesions in the right PV antrum as compared to the left PV antrum (35.5 ± 10.0Ω vs. 31.8 ± 9.2Ω, p = 0.032), and without any differences between LI drop in percentage (p = 0.193). On the other hand, a higher percentage and absolute LI drop were required in the anterior PV antrum to achieve successful lesion than that in the posterior PV antrum (20.8 ± 4.9% vs 18.3 ± 3.8%, p = 0.002; 35.6 ± 10.2Ω vs 31.4 ± 8.6Ω, p = 0.008). (Table 3 ) The mean percentage and absolute LI drop of each segment of PV ostium were illustrated in Fig. 3 . Table 3 Comparison of successful lesions of left and right walls; anterior and posterior walls. Parameters Successful lesions of left wall Successful lesions of right wall p value %LI drop † , % -19.0 ± 4.2 (18.2) -20.3 ± 4.9 (19.3) 0.193 Absolute LI drop † , Ω -31.8 ± 9.2 (31.0) -35.5 ± 10.0 (34.0) 0.032 Parameters Successful lesions of anterior wall Successful lesions of posterior wall p value %LI drop † , % -20.8 ± 4.9 (-19.7) -18.3 ± 3.8 (-17.5) 0.002 Absolute LI drop † , Ω -35.6 ± 10.2 (-34.5) -31.4 ± 8.6 (-29.5) 0.008 Abbreviation : %LI = local impedance drops in percentage, LI = local impedance Note : Mann-Whitney test, p < 0.05 indicated statistically significant, p < 0.001 indicated highly significant, † mean ± SD (median) 3.5 Local Impedance Drop in Successful Lesions from Different Initial Local Impedances Out of 142 successful lesions, there were 10.6% (n = 15), 47.2% (n = 67), 29.6% (n = 42) and 12.7% (n = 18) lesions with initial LI 190Ω, respectively. The comparison of LI drops in different initial LI groups are shown in Fig. 4 . The mean LI drop in percentage in the group with initial LI > 190Ω was significantly higher compared to other groups (P = 0.043). (Fig. 4 a). The mean absolute LI drop in the group with initial LI > 190Ω was also significantly higher (overall p < 0.001). (Fig. 4 b) The mean duration in the group with initial LI < 150Ω was significantly longer (p < 0.001). (Fig. 4 c) 3.6 Cut-off Values of Absolute and Percentage of the LI Drop In determining the successful lesions, the cut-off value of the LI drop in percentage was 16.2% (sensitivity 75%, specificity 63%) with an AUC of 0.79 [0.73–0.85] (p < 0.001). The cut-off value of the absolute LI drop was 26.5Ω (sensitivity 75%, specificity 69%) with an AUC of 0.81 [0.76–0.87] (p < 0.001). (Fig. 5 ) 3.7 Correlation between Absolute and Percentage of LI Drop A positive correlation between the absolute and percentage of the LI drop was identified (r = 0.92, p < 0.001), indicating that either of these two LI measurements determined successful and transmural lesions. (Fig. 6 ) 3.8 Local Impedance in Successful and Gap Lesions A total of 101 lesions from nine patients with gaps were obtained during post-ablation mapping. The initial LI (147.7 ± 12.2Ω vs 170.3 ± 19.1Ω, p < 0.001) and post-ablation LI (119.6 ± 9.3 vs 136.5 ± 15.6Ω, p < 0.001) were significantly lower in lesions with gap compared to successful lesions. There were significantly higher absolute LI drop in successful lesions than in lesions with gap (-33.8 ± 9.8Ω vs 28.1 ± 9.1Ω, p < 0.001). However, there were no differences in the percentage of LI drop in both successful and gap lesions (-19.7 ± 4.6% vs -18.9 ± 4.8%, p = 0.301). A longer duration was needed in lesions with gaps compared to successful lesions (11.6 ± 3.8s vs 9.8 ± 3.4s, p < 0.001) (Table 4 ) Table 4 Comparison of successful lesions and lesions with gap Parameters Successful lesions (n = 142) Lesions with gap (n = 101) p value Initial LI † , Ω 170.3 ± 19.1 (168.0) 147.7 ± 12.2 (146.0) < 0.001 Post-ablation LI † , Ω 136.5 ± 15.6 (135.5) 119.6 ± 9.3 (119.0) < 0.001 Absolute LI drop † , Ω − 33.8 ± 9.8 (-32.0) − 28.1 ± 9.1 (-27.0) < 0.001 %LI drop † , % − 19.7 ± 4.6 (-18.9) − 18.9 ± 4.8 (-18.6) 0.301 Duration † , s 9.8 ± 3.4 (8.9) 11.6 ± 3.8 (11.9) < 0.001 Abbreviation : %LI = local impedance drops in percentage, LI = local impedance, s = seconds Note : Mann-Whitney test, p < 0.05 indicated statistically significant, p < 0.001 indicated highly significant, † mean ± SD (median) 3.8 Outcome There were no complications that occurred during the procedure. The rate of AF recurrence in this study was 20% (n = 6) at 12 months follow-up post-ablation. 4. Discussion There were four main findings in the study. First, the LI drop was higher in successful lesions than in non-successful lesions. The initial LI was associated with the LI drop and duration of ablation in predicting successful lesions. Second, the initial LI in the right PV ostium was higher than in the left. LI drop in the anterior wall of the PV ostium was higher than that in the posterior wall of the PV ostium in predicting successful lesions. Third, the cut-off values in determining successful lesions were 16.2% and 26.5Ω. Lastly, there was a strong correlation between percentage and absolute LI drop. 4.1 Parameters of Local Impedance in Determining Successful Lesions LI drop was higher in successful lesions than in non-successful lesions. These findings were in line with the previous study, in which there was a strong correlation between initial LI and LI drop. 11 , 18 The higher the initial LI, the higher the percentage and absolute LI drops, and shorter duration of ablation were required to predict successful lesions. As LI reflects the characteristics of myocardial tissue, radiofrequency energy may penetrate better in relatively healthy myocardium with higher initial LI compared to scar tissue with lower initial LI. 19 4.2 Local Impedance Drop from Different Segments in Determining Successful Lesions The initial LI of the right PV ostium was significantly higher than the left side. These findings may reflect that the right PV antrum is adjacent to the atrial septum, which might have more myocardium than the left PV antrum. On the other hand, previous works reported significantly more scar tissue in the left inferior pulmonary vein (LIPV) area. 20 , 21 Mechanical compressions to LIPV caused by the descending aorta or by chronic LA stretching were believed to contribute to scar formation, 20 , 22 which may exhibit lower initial LI at the left PV antrum. When comparing the initial LI in the anterior and posterior PV antrum, there was no significant difference between the two groups (p = 0.181). However, both percentage and absolute LI drop were significantly higher in the anterior PV antrum. This reflected that the thicker anterior PV antrum required a higher LI drop in predicting the successful lesion, which was consistent with the previous studies. 18 4.3 Cut-off Values in Determining Successful Lesions The current study with HPSD 50W showed that an LI drop of 16.2% or 26.5Ω predicted successful lesions. A higher absolute LI drop was required as compared to previous works using the Intellanav Mifi catheters 23 or ablation combining of 40W-50W 18 . Further studies with a larger population are required to elucidate findings further. 4.4 Correlation between Percentage and Absolute Local Impedance Drop The current study showed that there was a strong correlation between percentage and absolute LI drop. Physicians may choose either option to determine the end point of ablation using the StablePoint catheter. 4.5 Parameters in the lesions with gap The initial and post-ablation LI were lower in lesions with gaps than in successful lesions, possibly due to gap lesions being partially ablated without achieving transmurality. This may further explain why partially ablated gap lesions required a longer duration for energy penetration than successful lesions. The absolute LI drop was higher in successful lesions than in the gap lesions, while there were no differences in the percentage of LI drop between both groups, which might be attributed to the different initial LI between both groups. 4.6 Comparisons of Local Impedance with Other Lesion Metrics LI provides real-time data on myocardial tissue characteristics and distinguishes between healthy and scarred myocardium. 24 The previously studied lesion metrics, which include lesion size index 25 , force-time integral 4 and ablation index 26 did not include descriptions of tissue characteristics. Radiofrequency energy penetration, hence, may not be equally distributed 19 , 27 and longer ablation duration may be required in scarred tissue. Therefore, a one-size-fits-all approach or a combination of different indirect parameters in the previous lesion metrics may not ensure the creation of transmural lesions in all segments. 4.6 Clinical Implications From the perspective of clinical utility, we prefer to apply the LI drop in percentage to determine transmurality. This strategy is relatively straightforward in order for the physician to determine the endpoint of each ablation lesion rather than relying on the absolute LI drop. To predict successful and transmural lesions, 20% and 23% LI drop might be sufficient when initial LI are ≤ 190Ω and > 190Ω, respectively. 5. Limitations There are a few limitations in the current study. First, this was a single-center retrospective study. Second, longer follow-up may be required to determine long-term success and AF freedom. Lastly, ablation lesions with local EGM < 0.3mV and tiny signals were not recruited in the analysis. 6. Conclusion In predicting successful lesions, initial LI was directly proportional to LI drop and inversely proportional to duration. A higher LI drop was required in the ablation of the anterior PV antrum compared to the posterior PV antrum, and right PV antrum than the left PV antrum. In addition, percentage and absolute LI drop could predict the successful and transmural lesions. Abbreviations AF: atrial fibrillation; AUC: area under the curve; CA: catheter ablation; ECG: electrocardiogram; EGM: electrogram; HPSD: high power short duration; LI: local impedance; PV: pulmonary vein; PVI: pulmonary vein isolation; RFCA: radiofrequency catheter ablation; ROC: receiver operating characteristic Declarations Ethics approval and consent to participate: The study was approved by the institutional review board of Taipei Veterans General Hospital (IRB-TPEVGH number: 2023-06-014CC). Consent for publication: Not applicable. Availability of data and materials: The datasets will be made available upon reasonable request to the corresponding author. Competing interests: None. Fundings: This study was funded by the Ministry of Science and Technology (Grant number: 106-2314-B-010-035-MY3, 109-2314-B-010-063, 110-2314-B-A49A-542, 111-2314-B-A49-007-MY3); Taipei Veterans General Hospital (Grant number: V109C-008, V110C-004, V111C-075, V112C-052); SZU-YUAN Research Foundation of Internal Medicine (109024, 110008, 111003, 112013). Shih-Lin Chang was the recipient of the funding award. The organizations involved in the awarding of grants had no role in the study design, data collection and analysis, decision to publish, or manuscript preparation. Authors' contributions: YKS, SLC: Conceptualization, writing the original manuscript, prepared figures and tables, analysis of data. FPC, YJL, LWL, YFH: Project administration, supervision. TCT, TFC, JNL: Methodology, review & editing. 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Szegedi N, Sallo Z, Perge P, Piros K, Nagy VK, Osztheimer I, et al. The role of local impedance drop in the acute lesion efficacy during pulmonary vein isolation performed with a new contact force sensing catheter-A pilot study. PLoS One. 2021;16(9):e0257050. Barkagan M, Leshem E, Shapira-Daniels A, Sroubek J, Buxton AE, Saffitz JE, et al. Histopathological Characterization of Radiofrequency Ablation in Ventricular Scar Tissue. JACC Clin Electrophysiol. 2019;5(8):920-31. Benito EM, Cabanelas N, Nunez-Garcia M, Alarcon F, Figueras IVRM, Soto-Iglesias D, et al. Preferential regional distribution of atrial fibrosis in posterior wall around left inferior pulmonary vein as identified by late gadolinium enhancement cardiac magnetic resonance in patients with atrial fibrillation. Europace. 2018;20(12):1959-65. Lee DK, Shim J, Choi JI, Kim YH, Oh YW, Hwang SH. Left Atrial Fibrosis Assessed with Cardiac MRI in Patients with Paroxysmal and Those with Persistent Atrial Fibrillation. Radiology. 2019;292(3):575-82. Caixal G, Althoff T, Garre P, Alarcon F, NunezGarcia M, Benito EM, et al. Proximity to the descending aorta predicts regional fibrosis in the adjacent left atrial wall: aetiopathogenic and prognostic implications. Europace. 2021;23(10):1559-67. Das M, Luik A, Shepherd E, Sulkin M, Laughner J, Oesterlein T, et al. Local catheter impedance drop during pulmonary vein isolation predicts acute conduction block in patients with paroxysmal atrial fibrillation: initial results of the LOCALIZE clinical trial. Europace. 2021;23(7):1042-51. Munkler P, Gunawardene MA, Jungen C, Klatt N, Schwarzl JM, Akbulak RO, et al. Local impedance guides catheter ablation in patients with ventricular tachycardia. J Cardiovasc Electrophysiol. 2020;31(1):61-9. Kanamori N, Kato T, Sakagami S, Saeki T, Kato C, Kawai K, et al. Optimal lesion size index to prevent conduction gap during pulmonary vein isolation. J Cardiovasc Electrophysiol. 2018;29(12):1616-23. Das M, Loveday JJ, Wynn GJ, Gomes S, Saeed Y, Bonnett LJ, et al. Ablation index, a novel marker of ablation lesion quality: prediction of pulmonary vein reconnection at repeat electrophysiology study and regional differences in target values. Europace. 2017;19(5):775-83. Garrott K, Laughner J, Gutbrod S, Sugrue A, Shuros A, Sulkin M, et al. Combined local impedance and contact force for radiofrequency ablation assessment. Heart Rhythm. 2020;17(8):1371-80. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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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-5113011","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":377077148,"identity":"8f46f895-21ad-42c3-b11d-1be00cedb0f5","order_by":0,"name":"Yoon Kee Siow","email":"","orcid":"","institution":"Department of Cardiology, Hospital Sultan Idris Shah, Serdang","correspondingAuthor":false,"prefix":"","firstName":"Yoon","middleName":"Kee","lastName":"Siow","suffix":""},{"id":377077149,"identity":"6270b02e-bcfa-4a3a-8fa7-3edee77de138","order_by":1,"name":"Shih-Lin Chang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABE0lEQVRIiWNgGAWjYLCCBwwHgCQziGBIYCNKSwJYC1sCTAtjA5AhQYQWHgMIm5AWfukG5g8JNXfkzfnXfN34o4Yhj0+6+fgDxh02dbi0SM45wCaRcOyZ4c4Zb7fd5jnGUMwmcyyxgfFMGk5bDG4AHZ/YcJhxw42z224zANltEjmGDYxth3Fqsb+RwPwBqMV+w40zz27++AfSkv8RqOU/blskEhgkgFoSN5zvYbvB2wa2hRGo5QBOLRJ3DrYB/XI4ecMNNrPbvH0SQC1phjMS25IlG3Bo4Z/dfPjDh5rDthvOHwY67JtN4vwZyQ8+fGyz48dlC4MEI9Q0oAsZ4LGRgFM9A1KM8R/Ap2wUjIJRMApGMgAAKVRhpL+F3cMAAAAASUVORK5CYII=","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":true,"prefix":"","firstName":"Shih-Lin","middleName":"","lastName":"Chang","suffix":""},{"id":377077150,"identity":"98bcd8f2-a1ac-4f9f-a4ca-65814e8b9e4c","order_by":2,"name":"Fa-Po Chung","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Fa-Po","middleName":"","lastName":"Chung","suffix":""},{"id":377077151,"identity":"893d6018-cd95-484d-a992-6b2648a0de04","order_by":3,"name":"Yenn-Jiang Lin","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yenn-Jiang","middleName":"","lastName":"Lin","suffix":""},{"id":377077152,"identity":"fe3e3817-73e5-47d5-9e14-6c8239c0fa57","order_by":4,"name":"Li-Wei Lo","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Li-Wei","middleName":"","lastName":"Lo","suffix":""},{"id":377077153,"identity":"520d9ba1-b200-4872-92e6-0e315eec5acd","order_by":5,"name":"Yu-Feng Hu","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yu-Feng","middleName":"","lastName":"Hu","suffix":""},{"id":377077154,"identity":"4b61dac8-d10b-44a2-910b-95fbe1d5968e","order_by":6,"name":"Ta-Chuan Tuan","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ta-Chuan","middleName":"","lastName":"Tuan","suffix":""},{"id":377077155,"identity":"f5b9cf1f-2071-469b-8ee7-fa23a07bac12","order_by":7,"name":"Tze-Fan Chao","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Tze-Fan","middleName":"","lastName":"Chao","suffix":""},{"id":377077156,"identity":"59374ffa-6a46-49b6-bd22-8bc5c068b282","order_by":8,"name":"Jo-Nan Liao","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jo-Nan","middleName":"","lastName":"Liao","suffix":""},{"id":377077157,"identity":"af865006-af9c-4508-9ab7-0bf52ea007d1","order_by":9,"name":"Chin-Yu Lin","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Chin-Yu","middleName":"","lastName":"Lin","suffix":""},{"id":377077158,"identity":"c55c618e-7611-425c-8366-f667c2cc9e53","order_by":10,"name":"Ting-Yung Chang","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ting-Yung","middleName":"","lastName":"Chang","suffix":""},{"id":377077159,"identity":"ffc95082-350d-4324-9aed-1c862f35ab51","order_by":11,"name":"Ling Kuo","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ling","middleName":"","lastName":"Kuo","suffix":""},{"id":377077160,"identity":"1ff399e0-2bf9-40a6-83f2-fe8df4056a6a","order_by":12,"name":"Jose Antonio L. Bautista","email":"","orcid":"","institution":"Section of Clinical Cardiac Electrophysiology, Heart Institute, St. Luke’s Medical Center – Global City","correspondingAuthor":false,"prefix":"","firstName":"Jose","middleName":"Antonio L.","lastName":"Bautista","suffix":""},{"id":377077161,"identity":"35155f37-f064-4a37-875a-0d40305ed4a8","order_by":13,"name":"Cheng-I Wu","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Cheng-I","middleName":"","lastName":"Wu","suffix":""},{"id":377077162,"identity":"e46c52e4-06f0-49af-aaff-d88917699bbf","order_by":14,"name":"Chih-Min Liu","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Chih-Min","middleName":"","lastName":"Liu","suffix":""},{"id":377077163,"identity":"f5ca0a2b-b1b7-4c3b-9fef-5d9b9cb8faec","order_by":15,"name":"Shin-Huei Liu","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Shin-Huei","middleName":"","lastName":"Liu","suffix":""},{"id":377077164,"identity":"4e73ad7d-b289-4d2b-86e4-b52cdc55fadf","order_by":16,"name":"Guan-Yi Li","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Guan-Yi","middleName":"","lastName":"Li","suffix":""},{"id":377077165,"identity":"1907324b-db98-4925-8091-d249d77687c9","order_by":17,"name":"Shang-Ju Wu","email":"","orcid":"","institution":"Cardiovascular Center, Taichung Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Shang-Ju","middleName":"","lastName":"Wu","suffix":""},{"id":377077166,"identity":"4b590e04-4d13-4519-920b-ee73e69286c7","order_by":18,"name":"Yu-Shan Huang","email":"","orcid":"","institution":"Heart Rhythm Center, Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yu-Shan","middleName":"","lastName":"Huang","suffix":""},{"id":377077168,"identity":"edd28c09-2fad-4489-bbe3-68a197c8c291","order_by":19,"name":"Dinh Son Ngoc Nguyen","email":"","orcid":"","institution":"University Medical Center","correspondingAuthor":false,"prefix":"","firstName":"Dinh","middleName":"Son Ngoc","lastName":"Nguyen","suffix":""},{"id":377077169,"identity":"a04d518f-9aca-4ab7-89e7-ae22664cbc9e","order_by":20,"name":"Dat Tran Cao","email":"","orcid":"","institution":"Arrhythmia Treatment Department, Cho Ray Hospital","correspondingAuthor":false,"prefix":"","firstName":"Dat","middleName":"Tran","lastName":"Cao","suffix":""},{"id":377077172,"identity":"d169822a-76ad-4781-85c2-0cdca4471923","order_by":21,"name":"Shih-Ann Chen","email":"","orcid":"","institution":"Cardiovascular Center, Taichung Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Shih-Ann","middleName":"","lastName":"Chen","suffix":""}],"badges":[],"createdAt":"2024-09-19 01:36:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5113011/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5113011/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":70386065,"identity":"52186d22-d5fd-497d-9fb1-ad8a97c06494","added_by":"auto","created_at":"2024-12-02 17:18:05","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":72383,"visible":true,"origin":"","legend":"\u003cp\u003eBipolar electrogram from ablation catheters of successful, non-successful and excluded (\u0026lt;0.3mV) lesions.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-5113011/v1/fe6c72747b7f111386d4b75c.png"},{"id":70385944,"identity":"8878414b-0c0c-4149-8831-c2882fe46f86","added_by":"auto","created_at":"2024-12-02 17:17:44","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":22911,"visible":true,"origin":"","legend":"\u003cp\u003eWorkflow of successful and non-successful ablation lesions. AW = anterior wall, PW = posterior wall.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-5113011/v1/25da90d9f379406fbdc484fb.png"},{"id":70386085,"identity":"66648d36-4cb7-4f59-8d34-1808b3ee71f1","added_by":"auto","created_at":"2024-12-02 17:18:10","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":75410,"visible":true,"origin":"","legend":"\u003cp\u003eMean percentage and absolute local impedance drop in antrum of each segment of pulmonary veins in successful lesions. RSPV: right superior pulmonary vein; RIPV: right inferior pulmonary vein; LSPV: left superior pulmonary vein; LIPV: left inferior pulmonary vein; S: superior; AS: anterior superior; AI: anterior inferior; I: inferior; PI: posterior inferior; PS: posterior superior.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-5113011/v1/4e33a8c642561160d82804be.png"},{"id":70386144,"identity":"1b378942-09cb-4ee8-96c9-1f30ec1841b5","added_by":"auto","created_at":"2024-12-02 17:18:25","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":79608,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Mean local impedance drops in percentage, (b) Mean absolute local impedance drops and (c) mean duration to achieve successful lesions, according to different initial local impedance. LI = Local impedance. † Significant with p\u0026lt;0.05 when compared to initial LI \u0026gt;190Ω, †† highly significant with p\u0026lt;0.001 when compared to initial LI \u0026gt;190Ω, # Significant with p\u0026lt;0.05 when compared to initial LI \u0026lt;150Ω.\u003c/p\u003e","description":"","filename":"Figure42.png","url":"https://assets-eu.researchsquare.com/files/rs-5113011/v1/3af8ae512ea81c4cdb6063e3.png"},{"id":70385941,"identity":"3d5468e5-8376-4212-b86d-0e3914c53a87","added_by":"auto","created_at":"2024-12-02 17:17:37","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":82083,"visible":true,"origin":"","legend":"\u003cp\u003eCut-off values of percentage and absolute local impedance drop. %LI = local impedance in percentage, LI = local impedance, AUC = area under the curve, ROC = receiver operating characteristic.\u003c/p\u003e","description":"","filename":"Figure5.png","url":"https://assets-eu.researchsquare.com/files/rs-5113011/v1/d0c983fd843324a01fc671b6.png"},{"id":70386192,"identity":"b72d1442-f21b-487e-8197-57cdb3f0acb3","added_by":"auto","created_at":"2024-12-02 17:18:38","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":78731,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation between absolute and percentage of LI Drop. LI = local impedance.\u003c/p\u003e","description":"","filename":"Figure6.png","url":"https://assets-eu.researchsquare.com/files/rs-5113011/v1/3a1d265573794e19715f2eb0.png"},{"id":80313549,"identity":"326b705b-b58e-4243-a03d-74605f43bd0b","added_by":"auto","created_at":"2025-04-10 11:53:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1693735,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5113011/v1/45707a37-bc68-463e-a888-f97999109b47.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Predictors of Transmural Lesion in High Power Short Duration Ablation of Atrial Fibrillation Guided by Local Impedance","fulltext":[{"header":"Highlights","content":"\u003cp\u003eIn predicting transmural lesions in atrial fibrillation ablation, initial local impedance (LI) was directly proportional to LI drop and inversely proportional to duration.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA strong correlation between percentage and absolute LI drop and either parameter predicted the successful and transmural lesions.\u003c/p\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eCatheter ablation (CA) is a safe and effective treatment in drug-refractory atrial fibrillation (AF).\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e The combination of different parameters during ablation, such as contact force, duration, power, or current, may provide radiofrequency CA (RFCA) guidance and improve long-term outcomes.\u003csup\u003e\u003cspan additionalcitationids=\"CR3 CR4\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e To achieve acute and long-term success of CA, transmurality of ablation lesions is considered the cornerstone in AF ablation.\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e The local electrogram (EGM) reflects the conduction gap and transmural lesions,\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e and this may be served as an indicator to define successful and transmural ablation lesions in a point-by-point manner. However, no single ablation dosage fits all myocardia. In real-world settings, myocardial tissues of the left atrium may interweave with healthy and scarred myocardial tissue. In such circumstances, local impedance (LI) offers real-time information on tissue characteristics before and during ablation.\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eOn the other hand, RFCA with high power short duration (HPSD) has been proven to be safe, fast, and effective in creating durable lesions of AF ablation.\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e However, the optimal parameters of LI for HPSD strategy using the ablation catheter with the contact force and LI remain unclear. The current study aimed to determine the optimal parameters and strategies for creating transmural lesions in pulmonary vein isolation (PVI) with the HPSD strategy.\u003c/p\u003e"},{"header":"2. Method","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Patient Selection\u003c/h2\u003e \u003cp\u003eThis single-center, retrospective study was conducted at Taipei Veterans General Hospital, Taiwan. The study duration started from 1st March 2022 to 31st October 2022. A total of 30 consecutive patients diagnosed with paroxysmal or persistent AF receiving HPSD 50W AF ablation for PVI with Rhythmia HDx system (Boston Scientific, Marlborough, MA, USA) were retrospectively recruited. Intellamap Orion high-resolution mapping catheters and Intellanav Stablepoint irrigated ablation catheters (Boston Scientific, Marlborough, MA, USA) were used for all patients in this study. The catheter was equipped with distal tips to measure the LI of myocardial tissue. It provides LI data, offering comprehensive tissue characteristics in real-time.\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e AF was defined as patients\u0026rsquo; electrocardiogram (ECG) or Holter monitoring showing irregular tracings without any repetitive or discernible P wave. Paroxysmal AF was defined as an AF episode that was terminated spontaneously or after relevant intervention within seven days, while persistent AF was defined as an AF episode that lasted beyond seven days.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e Baseline characteristics, comorbidities, medications and echocardiographic parameters were retrieved from hospital-based electronic medical records.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Ablation Procedure\u003c/h2\u003e \u003cp\u003eThe details of the procedure and protocol were described in our previous publications.\u003csup\u003e\u003cspan additionalcitationids=\"CR13 CR14\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e Anti-arrhythmic medications (except amiodarone) were withheld in all patients for more than five half-lives before the procedure. The procedures were conducted either under light sedation or general anesthesia. A 6F decapolar catheter (St. Jude Medical, Inc., St. Paul MN, USA) was placed into the coronary sinus via a right internal jugular venous access. Two transseptal atrial punctures were then performed under fluoroscopic guidance or transesophageal echocardiography. 8.5F SL-0 (Abbott Laboratories, Abbott Park, IL, USA) sheaths were inserted into the left atrium (LA) via right femoral venous accesses. Intellamap Orion high-resolution mapping catheter (Boston Scientific, Marlborough, MA, USA) was then positioned into the LA to create electroanatomical geometry. All patients then received PVI at bilateral pulmonary vein (PV) antra using an Intellanav Stablepoint irrigated ablation catheter. HPSD radiofrequency energy of 50W, with a maximum duration of less than 15 seconds and LI drop of 30% were applied for each lesion. Tests for entrance or exit block of the PV by pacing either from the coronary sinus or the PV, respectively, determining absence of electrical activities within the PV, or identifying PV dissociation were done after PVI. After PVI, the inducibility of AF was performed. The protocol used for AF inducibility was published in our previous study.\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e Non-PV foci were ablated if these were identified during inducibility testing. When atrial flutter or focal atrial tachycardia was induced, additional focal or linear ablation was performed after studying the mechanism of the arrhythmia. Cavotricuspid isthmus ablation was performed on all patients. Activated clotting time (ACT) was maintained at \u0026ge;\u0026thinsp;300 seconds during the procedure.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Successful, non-successful and gap lesions\u003c/h2\u003e \u003cp\u003eBipolar EGMs of ablation lesions for PVI were analyzed retrospectively with a scale of 32x and a sweep speed of 100 mm/s using the LabSystem Pro EP Recording System (Boston Scientific, Marlborough, MA, USA). The amplitude of pre-ablation lesions of \u0026ge;\u0026thinsp;0.3mV were included for analysis. A successful lesion was defined as a reduction of \u0026gt;\u0026thinsp;75% of the R wave in the QRS complex, or a complete disappearance of R\u0026rsquo; or RSR\u0026rsquo; patterns of the bipolar EGM\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e and post-ablation showed\u0026thinsp;\u0026lt;\u0026thinsp;0.3mV during voltage mapping. A lesion which did not meet these criteria was considered a non-successful lesion. The pre-ablation lesions that measured\u0026thinsp;\u0026lt;\u0026thinsp;0.3mV were not recruited into the analysis pool as the signals were very small. (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) The parameters of gap lesions were obtained in patients who did not achieve first-pass isolation, without applying EGM criteria.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Local Impedance of Ablation Lesion\u003c/h2\u003e \u003cp\u003eData from the Rhythmia HDx mapping system were retrospectively retrieved and labeled. The ablation lesions that met the bipolar EGM criteria were recruited into the analysis. Duration, force of each ablation lesion, initial and final LI (absolute and percentage drop) from the Rhythmia HDx mapping system were retrieved. Ablation lesions that contained the following were excluded from the analysis: lesions delivered in \u0026lt;\u0026thinsp;5 seconds duration, lesions with \u0026lt;\u0026thinsp;5 grams of contact force, lesions that were tagged manually by the mapping specialist due to instability of the ablation catheter, lesions with an initial LI of \u0026gt;\u0026thinsp;300Ω, and incomplete lesion data.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Follow-up and Detection of Arrhythmia Recurrence\u003c/h2\u003e \u003cp\u003eAfter the procedure, the patients were discharged and scheduled in the outpatient clinic for regular follow-up at two weeks and every 1\u0026ndash;3 months after the CA. Routine ECG was obtained at each outpatient follow-up, and a 7-day event recording was performed in the third month after the procedure. When the patients experienced any symptoms suggestive of arrhythmia, either a 24-hour Holter monitoring or cardiac event recording was conducted to ascertain the cause of the symptoms. AF recurrence was defined as documented AF or atrial tachycardia lasting for more than 30 seconds after the blanking period.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Data Analysis\u003c/h2\u003e \u003cp\u003eDemographic details of patients were presented in tables. All statistical tests were performed using IBM SPSS Statistics software version 26 (SPSS Inc, Chicago, IL, USA). Continuous variables were compared using the Student-t test and one-way ANOVA if the data distribution were normal, and the Mann-Whitney test and Kruskal-Wallis test if the data distribution were not normal. The receiver operating characteristic (ROC) curves were used to determine the area under the curve (AUC) of absolute and percentage of LI drop, and their cut-off values of specificity and sensitivity were determined with Youden Index \u0026amp; Index of Union. The correlation between absolute and percentage of LI drop was analyzed using Spearman correlation.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Patient Characteristics\u003c/h2\u003e \u003cp\u003eA total of 30 consecutive patients were included (76.7% male, mean 59.6\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0 years old). The mean LVEF was 58.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.0%, and the mean LAD was 38.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1mm. Most of these patients (93.3%, n\u0026thinsp;=\u0026thinsp;28) had paroxysmal AF. Baseline characteristics were summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\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 of the patients (n\u0026thinsp;=\u0026thinsp;30)\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=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eBaseline characteristics\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003en (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eAge (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e59.6\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eSex\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23 (76.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 (23.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eComorbidities\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDiabetes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (3.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHypertension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 (40.0%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoronary artery disease\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8 (26.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIschemic stroke\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (6.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCHA2DS2-VASc score\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eLVEF, % (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e58.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eLAD, mm (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e38.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eTypes of AF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eParoxysmal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e28 (93.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePersistent\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (6.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eAblation strategy:\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePVI and CTI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30 (100%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLinear ablation (Posterior wall isolation)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (3.33%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eMedications:\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eAntiarrhythmic medications\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFlecainide\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 (33.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePropafenone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11 (36.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAmiodarone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (10.0%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDronedarone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (6.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eBeta blockers\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8 (26.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eCalcium channel blockers\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 (23.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eAnticoagulants\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEdoxaban\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 (23.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRivaroxaban\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 (33.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDabigatran\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (10.0%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eProcedure time (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e195.8\u0026thinsp;\u0026plusmn;\u0026thinsp;59.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eFluoroscopy time (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e43.3\u0026thinsp;\u0026plusmn;\u0026thinsp;28.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAbbreviation\u003c/b\u003e: CTI\u0026thinsp;=\u0026thinsp;cavotricuspid isthmus isolation, LAD\u0026thinsp;=\u0026thinsp;left atrium diameter, LVEF\u0026thinsp;=\u0026thinsp;left ventricular ejection fraction, PVI\u0026thinsp;=\u0026thinsp;pulmonary vein isolation, SD\u0026thinsp;=\u0026thinsp;standard deviation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Ablation lesions\u003c/h2\u003e \u003cp\u003eA total of 210 ablation lesions met the bipolar EGM criteria of transmural lesions. Among these lesions, a total of 142 successful lesions (anterior wall: n\u0026thinsp;=\u0026thinsp;82, 39.0%; posterior wall: n\u0026thinsp;=\u0026thinsp;60, 28.6%) and 68 non-successful lesions were analyzed (anterior wall: n\u0026thinsp;=\u0026thinsp;54, 25.7%, posterior wall: n\u0026thinsp;=\u0026thinsp;14, 6.7%). (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) The mean initial LI of overall lesions was 166.6\u0026thinsp;\u0026plusmn;\u0026thinsp;18.4Ω. There was no difference between the initial LI of anterior and posterior lesions (165.3\u0026thinsp;\u0026plusmn;\u0026thinsp;18.8Ω vs. 169.0\u0026thinsp;\u0026plusmn;\u0026thinsp;17.7Ω, p\u0026thinsp;=\u0026thinsp;0.181). However, there was a significantly higher initial LI in the right than the left PV antrum lesions (174.4\u0026thinsp;\u0026plusmn;\u0026thinsp;16.0Ω vs. 160.7\u0026thinsp;\u0026plusmn;\u0026thinsp;18.0Ω, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Local Impedance Drop in Successful and Non-Successful Lesions\u003c/h2\u003e \u003cp\u003eIn the overall lesions, the mean LI drop in percentage was higher in successful lesions than in non-successful lesions (19.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6% vs. 15.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The mean absolute LI drop of overall lesions was also significantly higher in successful lesions compared to non-successful lesions (33.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.8Ω vs. 24.0\u0026thinsp;\u0026plusmn;\u0026thinsp;5.7Ω, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The mean percentage and absolute LI drop of successful lesions were higher than in non-successful lesions in different segments (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\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\u003eComparison of percentage and absolute local impedance drop in successful and non-successful lesions.\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\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSuccessful lesions\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNon-successful lesions\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\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\u003eOverall lesions - %LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, %\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-19.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6 (-18.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-15.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1 (-15.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOverall lesions - Absolute LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, Ω\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-33.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.8 (-32.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-24.0\u0026thinsp;\u0026plusmn;\u0026thinsp;5.7 (-24.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnterior - %LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, %\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-20.8\u0026thinsp;\u0026plusmn;\u0026thinsp;4.9 (-19.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-14.9\u0026thinsp;\u0026plusmn;\u0026thinsp;3.3 (-15.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnterior - Absolute LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, Ω\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-35.6\u0026thinsp;\u0026plusmn;\u0026thinsp;10.2 (-34.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-23.6\u0026thinsp;\u0026plusmn;\u0026thinsp;5.9 (-24.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePosterior - %LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, %\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-18.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8 (-17.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-15.8\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4 (-16.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.04\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePosterior - Absolute LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, Ω\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-31.4\u0026thinsp;\u0026plusmn;\u0026thinsp;8.6 (-29.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-25.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.7 (-26.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.016\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLeft - %LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, %\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-19.0\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2 (-18.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-14.9\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2 (-15.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLeft - Absolute LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, Ω\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-31.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.2 (-31.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-23.1\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5 (-23.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRight - %LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, %\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-20.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.9 (-19.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-16.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8 (-16.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRight - Absolute LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, Ω\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-35.5\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0 (-34.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-27.9\u0026thinsp;\u0026plusmn;\u0026thinsp;5.1 (-27.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAbbreviation\u003c/b\u003e: %LI\u0026thinsp;=\u0026thinsp;local impedance drops in percentage, LI\u0026thinsp;=\u0026thinsp;local impedance\u003c/p\u003e \u003cp\u003e\u003cb\u003eNote\u003c/b\u003e: Mann-Whitney test, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 indicated statistically significant, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001 indicated highly significant, \u003csup\u003e\u0026dagger;\u003c/sup\u003e mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD (median)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Impact of Initial Local Impedance in Successful Lesions\u003c/h2\u003e \u003cp\u003eA higher absolute LI drop was required for creating successful lesions in the right PV antrum as compared to the left PV antrum (35.5\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0Ω vs. 31.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.2Ω, p\u0026thinsp;=\u0026thinsp;0.032), and without any differences between LI drop in percentage (p\u0026thinsp;=\u0026thinsp;0.193). On the other hand, a higher percentage and absolute LI drop were required in the anterior PV antrum to achieve successful lesion than that in the posterior PV antrum (20.8\u0026thinsp;\u0026plusmn;\u0026thinsp;4.9% vs 18.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8%, p\u0026thinsp;=\u0026thinsp;0.002; 35.6\u0026thinsp;\u0026plusmn;\u0026thinsp;10.2Ω vs 31.4\u0026thinsp;\u0026plusmn;\u0026thinsp;8.6Ω, p\u0026thinsp;=\u0026thinsp;0.008). (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) The mean percentage and absolute LI drop of each segment of PV ostium were illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\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\u003eComparison of successful lesions of left and right walls; anterior and posterior walls.\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\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSuccessful lesions of left wall\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSuccessful lesions of right wall\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\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%LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, %\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-19.0\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2 (18.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-20.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.9 (19.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.193\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAbsolute LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, Ω\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-31.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.2 (31.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-35.5\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0 (34.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.032\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eParameters\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eSuccessful lesions of anterior wall\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eSuccessful lesions of posterior wall\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003ep value\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e%LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, %\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-20.8\u0026thinsp;\u0026plusmn;\u0026thinsp;4.9 (-19.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-18.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8 (-17.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAbsolute LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, Ω\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-35.6\u0026thinsp;\u0026plusmn;\u0026thinsp;10.2 (-34.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-31.4\u0026thinsp;\u0026plusmn;\u0026thinsp;8.6 (-29.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.008\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAbbreviation\u003c/b\u003e: %LI\u0026thinsp;=\u0026thinsp;local impedance drops in percentage, LI\u0026thinsp;=\u0026thinsp;local impedance\u003c/p\u003e \u003cp\u003e\u003cb\u003eNote\u003c/b\u003e: Mann-Whitney test, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 indicated statistically significant, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001 indicated highly significant, \u003csup\u003e\u0026dagger;\u003c/sup\u003e mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD (median)\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 \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Local Impedance Drop in Successful Lesions from Different Initial Local Impedances\u003c/h2\u003e \u003cp\u003eOut of 142 successful lesions, there were 10.6% (n\u0026thinsp;=\u0026thinsp;15), 47.2% (n\u0026thinsp;=\u0026thinsp;67), 29.6% (n\u0026thinsp;=\u0026thinsp;42) and 12.7% (n\u0026thinsp;=\u0026thinsp;18) lesions with initial LI\u0026thinsp;\u0026lt;\u0026thinsp;150Ω, 150Ω-170Ω, 170Ω-190Ω and \u0026gt;\u0026thinsp;190Ω, respectively. The comparison of LI drops in different initial LI groups are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The mean LI drop in percentage in the group with initial LI\u0026thinsp;\u0026gt;\u0026thinsp;190Ω was significantly higher compared to other groups (P\u0026thinsp;=\u0026thinsp;0.043). (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). The mean absolute LI drop in the group with initial LI\u0026thinsp;\u0026gt;\u0026thinsp;190Ω was also significantly higher (overall p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb) The mean duration in the group with initial LI\u0026thinsp;\u0026lt;\u0026thinsp;150Ω was significantly longer (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec)\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Cut-off Values of Absolute and Percentage of the LI Drop\u003c/h2\u003e \u003cp\u003eIn determining the successful lesions, the cut-off value of the LI drop in percentage was 16.2% (sensitivity 75%, specificity 63%) with an AUC of 0.79 [0.73\u0026ndash;0.85] (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The cut-off value of the absolute LI drop was 26.5Ω (sensitivity 75%, specificity 69%) with an AUC of 0.81 [0.76\u0026ndash;0.87] (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e)\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.7 Correlation between Absolute and Percentage of LI Drop\u003c/h2\u003e \u003cp\u003eA positive correlation between the absolute and percentage of the LI drop was identified (r\u0026thinsp;=\u0026thinsp;0.92, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), indicating that either of these two LI measurements determined successful and transmural lesions. (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e)\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.8 Local Impedance in Successful and Gap Lesions\u003c/h2\u003e \u003cp\u003eA total of 101 lesions from nine patients with gaps were obtained during post-ablation mapping. The initial LI (147.7\u0026thinsp;\u0026plusmn;\u0026thinsp;12.2Ω vs 170.3\u0026thinsp;\u0026plusmn;\u0026thinsp;19.1Ω, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and post-ablation LI (119.6\u0026thinsp;\u0026plusmn;\u0026thinsp;9.3 vs 136.5\u0026thinsp;\u0026plusmn;\u0026thinsp;15.6Ω, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) were significantly lower in lesions with gap compared to successful lesions. There were significantly higher absolute LI drop in successful lesions than in lesions with gap (-33.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.8Ω vs 28.1\u0026thinsp;\u0026plusmn;\u0026thinsp;9.1Ω, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). However, there were no differences in the percentage of LI drop in both successful and gap lesions (-19.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6% vs -18.9\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8%, p\u0026thinsp;=\u0026thinsp;0.301). A longer duration was needed in lesions with gaps compared to successful lesions (11.6\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8s vs 9.8\u0026thinsp;\u0026plusmn;\u0026thinsp;3.4s, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\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\u003eComparison of successful lesions and lesions with gap\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\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSuccessful lesions (n\u0026thinsp;=\u0026thinsp;142)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLesions with gap (n\u0026thinsp;=\u0026thinsp;101)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\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\u003eInitial LI\u003csup\u003e\u0026dagger;\u003c/sup\u003e, Ω\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e170.3\u0026thinsp;\u0026plusmn;\u0026thinsp;19.1 (168.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e147.7\u0026thinsp;\u0026plusmn;\u0026thinsp;12.2 (146.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePost-ablation LI\u003csup\u003e\u0026dagger;\u003c/sup\u003e, Ω\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e136.5\u0026thinsp;\u0026plusmn;\u0026thinsp;15.6 (135.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e119.6\u0026thinsp;\u0026plusmn;\u0026thinsp;9.3 (119.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAbsolute LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, Ω\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;\u0026thinsp;33.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.8 (-32.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;\u0026thinsp;28.1\u0026thinsp;\u0026plusmn;\u0026thinsp;9.1 (-27.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e%LI drop\u003csup\u003e\u0026dagger;\u003c/sup\u003e, %\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;\u0026thinsp;19.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6 (-18.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;\u0026thinsp;18.9\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8 (-18.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.301\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDuration\u003csup\u003e\u0026dagger;\u003c/sup\u003e, s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.8\u0026thinsp;\u0026plusmn;\u0026thinsp;3.4 (8.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11.6\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8 (11.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAbbreviation\u003c/b\u003e: %LI\u0026thinsp;=\u0026thinsp;local impedance drops in percentage, LI\u0026thinsp;=\u0026thinsp;local impedance, s\u0026thinsp;=\u0026thinsp;seconds\u003c/p\u003e \u003cp\u003e\u003cb\u003eNote\u003c/b\u003e: Mann-Whitney test, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 indicated statistically significant, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001 indicated highly significant, \u003csup\u003e\u0026dagger;\u003c/sup\u003e mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD (median)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.8 Outcome\u003c/h2\u003e \u003cp\u003eThere were no complications that occurred during the procedure. The rate of AF recurrence in this study was 20% (n\u0026thinsp;=\u0026thinsp;6) at 12 months follow-up post-ablation.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThere were four main findings in the study. First, the LI drop was higher in successful lesions than in non-successful lesions. The initial LI was associated with the LI drop and duration of ablation in predicting successful lesions. Second, the initial LI in the right PV ostium was higher than in the left. LI drop in the anterior wall of the PV ostium was higher than that in the posterior wall of the PV ostium in predicting successful lesions. Third, the cut-off values in determining successful lesions were 16.2% and 26.5Ω. Lastly, there was a strong correlation between percentage and absolute LI drop.\u003c/p\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Parameters of Local Impedance in Determining Successful Lesions\u003c/h2\u003e \u003cp\u003eLI drop was higher in successful lesions than in non-successful lesions. These findings were in line with the previous study, in which there was a strong correlation between initial LI and LI drop.\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e The higher the initial LI, the higher the percentage and absolute LI drops, and shorter duration of ablation were required to predict successful lesions. As LI reflects the characteristics of myocardial tissue, radiofrequency energy may penetrate better in relatively healthy myocardium with higher initial LI compared to scar tissue with lower initial LI.\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Local Impedance Drop from Different Segments in Determining Successful Lesions\u003c/h2\u003e \u003cp\u003eThe initial LI of the right PV ostium was significantly higher than the left side. These findings may reflect that the right PV antrum is adjacent to the atrial septum, which might have more myocardium than the left PV antrum. On the other hand, previous works reported significantly more scar tissue in the left inferior pulmonary vein (LIPV) area.\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e Mechanical compressions to LIPV caused by the descending aorta or by chronic LA stretching were believed to contribute to scar formation, \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e which may exhibit lower initial LI at the left PV antrum.\u003c/p\u003e \u003cp\u003eWhen comparing the initial LI in the anterior and posterior PV antrum, there was no significant difference between the two groups (p\u0026thinsp;=\u0026thinsp;0.181). However, both percentage and absolute LI drop were significantly higher in the anterior PV antrum. This reflected that the thicker anterior PV antrum required a higher LI drop in predicting the successful lesion, which was consistent with the previous studies.\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Cut-off Values in Determining Successful Lesions\u003c/h2\u003e \u003cp\u003eThe current study with HPSD 50W showed that an LI drop of 16.2% or 26.5Ω predicted successful lesions. A higher absolute LI drop was required as compared to previous works using the Intellanav Mifi catheters\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e or ablation combining of 40W-50W\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Further studies with a larger population are required to elucidate findings further.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec23\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Correlation between Percentage and Absolute Local Impedance Drop\u003c/h2\u003e \u003cp\u003eThe current study showed that there was a strong correlation between percentage and absolute LI drop. Physicians may choose either option to determine the end point of ablation using the StablePoint catheter.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003e4.5 Parameters in the lesions with gap\u003c/h2\u003e \u003cp\u003eThe initial and post-ablation LI were lower in lesions with gaps than in successful lesions, possibly due to gap lesions being partially ablated without achieving transmurality. This may further explain why partially ablated gap lesions required a longer duration for energy penetration than successful lesions. The absolute LI drop was higher in successful lesions than in the gap lesions, while there were no differences in the percentage of LI drop between both groups, which might be attributed to the different initial LI between both groups.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec25\" class=\"Section2\"\u003e \u003ch2\u003e4.6 Comparisons of Local Impedance with Other Lesion Metrics\u003c/h2\u003e \u003cp\u003eLI provides real-time data on myocardial tissue characteristics and distinguishes between healthy and scarred myocardium.\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e The previously studied lesion metrics, which include lesion size index\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e, force-time integral\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e and ablation index\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e did not include descriptions of tissue characteristics. Radiofrequency energy penetration, hence, may not be equally distributed\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e and longer ablation duration may be required in scarred tissue. Therefore, a one-size-fits-all approach or a combination of different indirect parameters in the previous lesion metrics may not ensure the creation of transmural lesions in all segments.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec26\" class=\"Section2\"\u003e \u003ch2\u003e4.6 Clinical Implications\u003c/h2\u003e \u003cp\u003eFrom the perspective of clinical utility, we prefer to apply the LI drop in percentage to determine transmurality. This strategy is relatively straightforward in order for the physician to determine the endpoint of each ablation lesion rather than relying on the absolute LI drop. To predict successful and transmural lesions, 20% and 23% LI drop might be sufficient when initial LI are \u0026le;\u0026thinsp;190Ω and \u0026gt;\u0026thinsp;190Ω, respectively.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Limitations","content":"\u003cp\u003eThere are a few limitations in the current study. First, this was a single-center retrospective study. Second, longer follow-up may be required to determine long-term success and AF freedom. Lastly, ablation lesions with local EGM\u0026thinsp;\u0026lt;\u0026thinsp;0.3mV and tiny signals were not recruited in the analysis.\u003c/p\u003e"},{"header":"6. Conclusion","content":"\u003cp\u003eIn predicting successful lesions, initial LI was directly proportional to LI drop and inversely proportional to duration. A higher LI drop was required in the ablation of the anterior PV antrum compared to the posterior PV antrum, and right PV antrum than the left PV antrum. In addition, percentage and absolute LI drop could predict the successful and transmural lesions.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eAF: atrial fibrillation; AUC: area under the curve; CA: catheter ablation; ECG: electrocardiogram; EGM: electrogram; HPSD: high power short duration; LI: local impedance; PV: pulmonary vein; PVI: pulmonary vein isolation; RFCA: radiofrequency catheter ablation; ROC: receiver operating characteristic\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 was approved by the institutional review board of Taipei Veterans General Hospital (IRB-TPEVGH number: 2023-06-014CC).\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 will be made available upon reasonable request to the corresponding author.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFundings:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was funded by the Ministry of Science and Technology (Grant number: 106-2314-B-010-035-MY3, 109-2314-B-010-063, 110-2314-B-A49A-542, 111-2314-B-A49-007-MY3); Taipei Veterans General Hospital (Grant number: V109C-008, V110C-004, V111C-075, V112C-052); SZU-YUAN Research Foundation of Internal Medicine (109024, 110008, 111003, 112013). Shih-Lin Chang was the recipient of the funding award. The organizations involved in the awarding of grants had no role in the study design, data collection and analysis, decision to publish, or manuscript preparation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eYKS, SLC: Conceptualization, writing the original manuscript, prepared figures and tables, analysis of data. FPC, YJL, LWL, YFH: Project administration, supervision. TCT, TFC, JNL: Methodology, review \u0026amp; editing. CYL, TYC, LK: Investigation \u0026amp; validation. JALB, CIW, CML, SHL, GYL, SJW, YSH, DSNN, DTC: Review, editing \u0026amp; validation. SAC: Conceptualization, supervision, validation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHindricks G, Potpara T, Dagres N, Arbelo E, Bax JJ, Blomstrom-Lundqvist C, et al. 2020 ESC Guidelines for the diagnosis and management of atrial fibrillation developed in collaboration with the European Association for Cardio-Thoracic Surgery (EACTS): The Task Force for the diagnosis and management of atrial fibrillation of the European Society of Cardiology (ESC) Developed with the special contribution of the European Heart Rhythm Association (EHRA) of the ESC. Eur Heart J. 2021;42(5):373-498.\u003c/li\u003e\n\u003cli\u003eHussein A, Das M, Riva S, Morgan M, Ronayne C, Sahni A, et al. 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J Cardiovasc Electrophysiol. 2020;31(1):61-9.\u003c/li\u003e\n\u003cli\u003eKanamori N, Kato T, Sakagami S, Saeki T, Kato C, Kawai K, et al. Optimal lesion size index to prevent conduction gap during pulmonary vein isolation. J Cardiovasc Electrophysiol. 2018;29(12):1616-23.\u003c/li\u003e\n\u003cli\u003eDas M, Loveday JJ, Wynn GJ, Gomes S, Saeed Y, Bonnett LJ, et al. Ablation index, a novel marker of ablation lesion quality: prediction of pulmonary vein reconnection at repeat electrophysiology study and regional differences in target values. Europace. 2017;19(5):775-83.\u003c/li\u003e\n\u003cli\u003eGarrott K, Laughner J, Gutbrod S, Sugrue A, Shuros A, Sulkin M, et al. Combined local impedance and contact force for radiofrequency ablation assessment. Heart Rhythm. 2020;17(8):1371-80.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"atrial fibrillation, ablation, initial local impedance, impedance drop","lastPublishedDoi":"10.21203/rs.3.rs-5113011/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5113011/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe impact of local impedance (LI) drop in high power short duration (HPSD) for atrial fibrillation (AF) remains unclear.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eObjective\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003eThis study aimed to assess the parameters predicting transmural lesions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethod:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThirty patients (76.7% male, mean 59.6±10.0 years old) with AF who underwent radiofrequency ablation were enrolled. Ablation lesions of pulmonary vein isolation (PVI) were created by HPSD (50W, ≤15s and LI drop ≤30%). Successful and non-successful lesions were defined by electrogram criteria. Absolute and percentage LI drop of ablation lesions were recorded.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOf 210 ablation lesions included, 67.6% (n=142) were successful lesions. The mean percentage and absolute LI drop were higher in successful than in non-successful lesions (19.7±4.6% vs. 15.1±3.1%, p\u0026lt;0.001; 33.8±9.8Ω vs. 24.0±5.7Ω, p\u0026lt;0.001). To create successful lesions, higher absolute LI drop was required in the right than in the left PV antrum (35.5±10.0Ω vs. 31.8±9.2Ω, p=0.032), while higher percentage and absolute LI drop were required in the anterior than in the posterior PV antrum (20.8±4.9% vs. 18.3±3.8%, p=0.002; 35.6±10.2Ω vs. 31.4±8.6Ω, p=0.008). Among 142 successful lesions, the higher initial LI group (\u0026gt;190 Ω) had a higher mean percentage and absolute LI drop, and shorter mean duration of ablation compared with lower initial LI groups (\u0026lt;150Ω, 150Ω-170Ω, 170Ω-190Ω). The cut-off values of percentage and absolute LI drop were 16.2% and 26.5Ω, respectively, to predict the successful lesions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn successful lesion of PVI, initial LI was associated with LI drop and duration of ablation. The LI could predict transmural lesions and guide HPSD ablation.\u003c/p\u003e","manuscriptTitle":"Predictors of Transmural Lesion in High Power Short Duration Ablation of Atrial Fibrillation Guided by Local Impedance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-02 16:25:17","doi":"10.21203/rs.3.rs-5113011/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"fb83ad4b-1ea0-4e6f-b518-4b69c8cf7cc0","owner":[],"postedDate":"December 2nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-04-10T11:53:13+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-02 16:25:17","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5113011","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5113011","identity":"rs-5113011","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}