Outcomes of Catheter Ablation for Typical Atrioventricular Nodal Reentrant Tachycardia with Low Power Energy of 20 W: A Prospective Multicenter Study

Outcomes of Catheter Ablation for Typical Atrioventricular Nodal Reentrant Tachycardia with Low Power Energy of 20 W: A Prospective Multicenter Study | 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 Outcomes of Catheter Ablation for Typical Atrioventricular Nodal Reentrant Tachycardia with Low Power Energy of 20 W: A Prospective Multicenter Study Lae-Young Jung, Chang Hee Kwon, In Geol Song, Ji Hyun Lee, Minsu Kim This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7444266/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 Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common form of supraventricular tachycardia, and catheter ablation is a well-established treatment. However, the risk of atrioventricular (AV) block requiring permanent pacemaker implantation remains a significant concern, with reported incidence rates ranging from 0.1% to 0.8%. Objective This study aimed to assess the clinical outcomes and safety of slow pathway ablation using low-power energy (20 W) for typical AVNRT. Methods This prospective multicenter trial enrolled 203 patients (mean age 54.4±17.3 years, 121 women) who underwent slow pathway ablation with 20 W between May 2017 and February 2022. Ablation was performed from the posterior region of the triangle of Koch until a slow-accelerated junctional rhythm was observed. Results Among the 203 patients who underwent ablation, 170 (83.7%) achieved successful ablation with 20 W. Of the 33 patients (16.3%) who did not achieve success with 20 W, 17 (8.4%) required 25 W, while 16 (7.9%) required an energy level greater than 25 W. A younger age (43.8±17.1 vs. 56.4±16.5 years, p<0.001) and a higher pre-ablation heart rate (84.8±11.8 vs. 77.3±10.8 bpm, p<0.001) were associated with failure at 20 W. Transient AV block occurred in 4 patients (1.9%). No patients developed permanent AV block requiring pacemaker implantation. The recurrence rate following low-power ablation was 0.9%. Over a mean follow-up of 18.3±4.1 months, no long-term complications were reported. Conclusion Low-power ablation using 20 W is a safe and effective strategy for typical AVNRT, with no cases of permanent AV block observed in this cohort. Atrioventricular nodal reentrant tachycardia Catheter ablation Radiofrequency ablation Treatment outcome Prospective studies Introduction Slow pathway modification with radiofrequency (RF) energy is the gold standard for treating atrioventricular nodal reentrant tachycardia (AVNRT), given its high success rates. 1 The primary complication of AVNRT catheter ablation is complete atrioventricular (AV) block, with an incidence ranging from 0.1–0.8%. 2–4 Additionally, the incidence of permanent pacemaker implantation due to late AV block (> 1 month after ablation) has been reported at 0.4%. 5 Despite the clinically relevant risk of acute and late AV block, limited data are available regarding the optimal RF power settings for AVNRT ablation. Slow pathway modification is typically performed by identifying the anatomical target site, confirming the electrogram potential, and initiating ablation. While this general approach is widely adopted, there is no standardized protocol for the optimal energy delivery or endpoint definition, leading to variability in practice among operators. Studies have reported a wide range of energy levels, from 20W to 50W, with some utilizing gradual up-titration strategies. 6 – 8 However, a study by Bortone et al. reported that slow-accelerated junctional rhythm occurred at an average of 18.5 W during slow pathway modification. 9 Additionally, recent study by Kawaji et al. using a near-field detection algorithm–guided approach has shown that the slow pathway is relatively superficial, suggesting that ablation can be effectively performed with lower energy levels. 10 Despite these findings, data on low-energy ablation remain limited, with most studies conducted in a single center settings and involving only a small number of selected patients. 8 , 11 The present study evaluates slow pathway ablation using low power energy (20 W), demonstrating favorable clinical outcomes with a low risk of procedure-related permanent AV block. Methods Study patients We conducted a prospective multicenter trial at three tertiary referral hospitals between May 2017 and February 2022. A total of 203 patients undergoing slow pathway ablation for typical AVNRT with 20 W energy were enrolled. All patients provided informed consent before the electrophysiology study and catheter ablation procedure. The study protocol was reviewed and approved by the institutional review board of Chungnam National University Sejong Hospital (CNUH201906005006-HE002). Definition Typical AVNRT was defined by an atrial-His/His-atrial ratio > 1 and a His-atrial interval ≤ 70 msec. 12 The echo window was defined as the interval during programmed stimulation with 10 msec decrements, during which a single echo was observed in the post-ablation period. Transient AV block was defined as second-degree AV block (Mobitz type I or II) or third-degree AV block that fully resolved during the electrophysiology study. Recurrence was defined as documented supraventricular tachycardia on a 12-lead ECG, 24-hour Holter monitoring, portable ECG devices, or an electrophysiology study. Electrophysiology study and ablation RF pulses of up to 60 s were applied at optimal sites with a maximum temperature of 60°C. 13 Electrophysiology studies were conducted in the fasting state after obtaining written informed consent. All patients discontinued antiarrhythmic medications for at least 5 half-lives. Conscious sedation with midazolam, propofol, and fentanyl was administered. Venous access was obtained through both groins, and multipolar catheters were placed in standard positions: the high right atrium, coronary sinus, right ventricular apex, and His bundle. Sustained typical AVNRT was induced in all patients using programmed atrial and ventricular stimulation at different cycle lengths, with isoproterenol infusion as needed. Slow pathway ablation followed standard techniques 14 , 15 using three types of conventional 4-mm ablation catheters (Blazer®, Boston Scientific, Natick, MA, USA; EZ Steer®, Biosense Webster Inc. Irvine, CA, USA; Safire®, St. Jude Medical, Minnetonka, MN, USA). The ablation catheter was positioned in the posterior part of atrial septum, between the tricuspid annulus and coronary sinus ostium, until the atrial- to-ventricular electrogram ratio ranged from approximately 1:10 to 1:3, with a delay in the atrial electrogram relative to the His bundle recording. When multicomponent or low-amplitude high frequent potentials were identified, RF energy was applied for up to 20 seconds until a junctional rhythm with 1:1 retrograde ventriculoatrial (VA) conduction was observed. Once slow-accelerated junctional rhythm, defined by ≥ 5 junctional beats with a mean cycle of > 350 msec, 16 indicated effective modification, and energy delivery was continued for up to 60 seconds. If fast-accelerated junctional rhythm (defined by ≥ 5 junctional beats with a mean cycle length of ≤ 350 msec 16 ) or VA block occurred during junctional ectopy, 17 RF application was immediately discontinued, and the ablation catheter was repositioned. Acute successful slow pathway ablation for AVNRT was defined as the non-inducibility of typical AVNRT, regardless of the presence of an AH jump or fewer than two echo beats, with or without isoproterenol administration. If slow-accelerated junctional rhythm was not observed or if typical AVNRT was re-induced after appropriate slow pathway ablation with 20 W, the procedure was considered as a failure of low power energy ablation. In such cases, patients underwent repeat ablation with 25 W or higher. Failed ablation for AVNRT was defined as termination of the procedure despite reproducible induction of tachycardia. The location of successful slow pathway ablation was categorized into three regions. The posterior region included sites along the tricuspid septal annulus extending to the most inferoposterior aspect of the interatrial septum, adjacent to the coronary sinus ostium. The anterior region was defined as sites where the ablation catheter was positioned near the His-bundle catheter along the tricuspid septal annulus. The mid-region was located between the posterior and anterior regions. Study outcome The primary efficacy endpoint was to assess the acute procedural success rate and recurrence rate following ablation. The safety endpoint evaluated the incidence of serious adverse events, particularly AV block, during the procedure and follow-up. An independent clinical events committee adjudicated procedure-related serious adverse events. Additionally, electrophysiological changes during the procedure were analyzed. Follow-up Routine follow-up visits were scheduled at 1, 6, 12, 18, and, 24 months post-procedure. Patients were also instructed to contact our team if they experienced symptoms of tachycardia or bradycardia. Statistical analysis Continuous variables are presented as mean ± standard deviation, while categorical variables are expressed as frequencies. Group differences were assessed using χ 2 test for categorical variables and Student's t-test for continuous variables. Statistical analysis was performed using commercially available software (SPSS 21 for Windows; SPSS Inc., Chicago, IL, USA). Results Baseline characteristics The baseline clinical characteristics of the study patients are summarized in Table 1 . The mean age of the 203 patients was 54.4 ± 17.3 years, with 82 men and 121 women. Hypertension was present in 68 patients (33.5%), while diabetes was reported in 31 patients (15.3%). Table 1 Clinical characteristics of the study patients Number of patients 203 Age (years) 54.4 ± 17.3 Female, n (%) 121 (59.6%) Hypertension 68 (33.5%) Diabetes 31 (15.3%) Coronary artery disease 12 (5.9%) Valvular heart disease Chronic lung disease Stroke 0 0 4 (2.0%) Values are expressed as the mean ± standard deviation or n (%). Ablation procedures Procedural data are summarized in Table 2 . Slow pathway ablation using 20 W was acutely successful in 170 of 203 patients (83.7%). The successful ablation sites were located in the posterior region in 83 cases, the mid-region in 72 cases, and the anterior region of the triangle of Koch (ToK) in 15 cases. The mean number of RF applications required to achieve slow-accelerated junctional rhythm was 6.1 ± 4.8 in the 20 W group and 16.8 ± 14.9 in patients requiring higher energy. Table 2 Study outcomes Acute procedural outcomes Number of patients 203 Ablation energy Success at the initial 20W Failure at 20W, then success after increasing 25W Energy exceeding 25W Result of ablation 170 (83.7%) 17 (8.4%) 16 (7.9%) Slow pathway ablation 87 (42.9%) Slow pathway modification Failed ablation 113 (55.6%) 3 (1.5%) Transient VA block during junctional ectopy 48 (23.6%) Transient AV block (second- or third-degree AV block) 4 (1.9%) Second degree (Mobitz type I) 3 (1.5%) Third degree 1 (0.5%) Long term outcomes Permanent AV block (second- or third-degree AV block) Late recurrence 0 2 (0.9%) AV, atrioventricular; VA, ventriculoatrial. Table 3 Comparison between the group that succeeded at 20W and above 20W Clinical characteristics 20W (n = 170) Above 20W (n = 33) P -value Age 56.4 ± 16.5 43.8 ± 17.1 < 0.001 Sex 67 (36.4%) 15 (45.5%) 0.517 Hypertension 58 (34.1%) 10 (30.3%) 0.671 Diabetes 31 (18.2%) 0 0.008 Coronary artery disease 9 (5.3%) 3 (9.1%) 0.397 Stroke 4 (2.4%) 0 0.373 Procedural characteristics Ablation site 0.060 Ablation at the posterior region of the ToK, n (%) 83 (48.8%) 9 (27.3%) Ablation at the mid-region of the ToK, n (%) 72 (42.4%) 18 (54.5%) Ablation at the anterior region of ToK, n (%) 15 (8.8%) 6 (18.2%) Mean RF applications 6.1 ± 4.8 16.8 ± 14.9 < 0.001 Session with obtained slow-accelerated junctional rhythm 4.9 ± 4.6 8.4 ± 6.4 0.002 Procedure duration (min) 82.2 ± 22.0 112.4 ± 30.1 < 0.001 Fluoroscopic time (min) 13.2 ± 8.2 21.5 ± 11.2 < 0.001 HR before ablation 77.3 ± 10.8 84.8 ± 11.8 < 0.001 RF duration (sec) 81.7 ± 53.5 85.4 ± 17.3 < 0.001 Total RF ablation number 6.1 ± 4.8 16.8 ± 14.9 < 0.001 Total RF ablation time (sec) 221.3 ± 140.8 496 ± 442.3 0.001 Values are expressed as the mean ± standard deviation or n (%). AV, atrioventricular; HR, heart rate; RF, radiofrequency; ToK, triangle of Koch. Among 33 patients who failed ablation at 20 W, 17 (8.4%) achieved success with 25 W, while 16 (7.9%) required an energy level exceeding 25 W. In all cases, ablation was performed in the posterior or mid-region of ToK. Three patients (1.5%) ultimately failed slow pathway ablation. Compared to those successfully treated with 20 W, patients requiring higher power were significantly younger (43.8 ± 17.1 vs 56.4 ± 16.5 years, P < 0.001) and had a higher pre-ablation heart rate (84.8 ± 11.8 vs 77.3 ± 10.8 bpm, P < 0.001). VA block during junctional ectopy occurred in 48 patients (23.6%) during RF application. Transient anterograde AV block was observed in 4 patients (1.9%), including three cases of second-degree Mobitz type I blocks and one case of third-degree AV block. All transient AV blocks occurred either after the acceleration of slow-accelerated junctional rhythm or during VA block assessment, prompting immediate cessation of RF application. All cases were resolved completely before the end of the procedure. No patient developed a permanent AV block requiring pacemaker implantation. Follow-up observation Patients were followed for an average of 18.3 ± 4.1 months. Among those who experienced transient AV block during the procedure, no recurrence of AV block was observed during follow-up, and no patients required permanent pacemaker implantation. AVNRT recurred in two patients (0.9%), both of whom underwent repeat ablation with 30 W at the ToK. No adverse effects were reported during the follow-up period. Discussion The findings of this study demonstrate that low-power RF application for slow pathway modification is both effective and safe in the patients with typical AVNRT. In this study, 83.7% of patients undergoing AVNRT ablation successfully completed the procedure using a low energy of 20 W. A younger age and a higher pre-ablation heart rate were associated with failure at 20 W. Over a mean follow-up of 18.3 ± 4.1 months, no patients developed permanent AV block requiring pacemaker implantation and the recurrence rate following low-power ablation was 0.9%. Initiating the procedure with low energy, followed by higher energy application if needed, represents a safe and effective strategy compared to conventional approaches. The risk of permanent AV block is not limited to the immediate post-procedural period but can persist for months or even years. Previous studies have reported cases of very late-onset second- or third-degree AV block following catheter ablation for AVNRT. 18 , 19 Transient retrograde VA block during junctional rhythm or the development of fast-accelerated junctional rhythm are significant predictors of AV block in patients undergoing slow pathway ablation. Therefore, careful monitoring of these signs and discontinuing the procedure before permanent damage occurs are crucial for preventing irreversible AV block. In this study, 48 patients (23.6%) experienced transient VA block during the procedure; however, immediate cessation of energy delivery prevented progression to permanent AV block. Although the exact pathophysiologic mechanism remains unclear, it is speculated that assessing transient VA block during junctional ectopy and promptly stopping RF application at a low energy level of 20 W helped to minimize irreversible damage. Previous studies have proposed several strategies to minimize the risk of AV block, including transient discontinuation of RF energy upon the development of junctional rhythm and performing multiple ablations with progressively longer durations ≤ 30 seconds. 20 Another technique, introduced by Liberman et al., 21 suggested that rapid atrial pacing during ablation could help to ensure intact anterograde AV conduction. However, if junctional rhythm is slightly faster than the pacing cycle length, it may be difficult to identify in this setting. This could delay RF termination by a few seconds, increasing the risk of permanent AV block. Several studies have also explored the use of low-power ablation to reduce AV block risk. 8 , 11 , 22 , 23 Table 4 summarizes these previous findings along with the results of the present study. Dechering & Schleberger et al. compared high-power (50 W) and moderate-power (30 W) ablation, reporting similar acute success rates but a slightly higher recurrence in the moderate-power (30W) group. 22 Langberg et al. investigated a stepwise energy escalation approach, starting as low as 10 W and increasing up to 30 W, demonstrating that gradual power titration effectively eliminated the slow pathway while avoiding unnecessary high-power applications. 11 Bortone et al. also proposed a gradual power titration starting from low energy, which proved to be a safe and controlled approach. 8 In the present study, we further validated the efficacy of an initial low-power ablation strategy (20 W), with stepwise escalation only when necessary. Among previous studies utilizing an up-titration strategy starting from low energy, junctional rhythm was found to be unstable at energy levels below 20 W. Therefore, 20 W was considered the minimum effective threshold, forming the basis for the initial ablation energy (20 W) in this study. This approach resulted in a high acute success rate (98.5%) and a low recurrence rate (0.9%), with no cases of permanent AV block. Table 4 Comparison of studies evaluating energy power for slow pathway ablation Jung & Kwon et al. Dechering & Schleberger et al. 22 Langberg et al. 11 Bortone et al. 8 Wasmer et al. 4 Katritsis et al. 23 Study type Prospective Randomized (50W vs. 30W) Randomized (Anterior vs. Posterior) Retrospective Retrospective Prospective Number 203 (170 in 20W, 33 in above 20W) 634 (342 in 50W vs. 292 in 30W) 50 (28 vs. 22) 468 2,101 1,087 Energy power (watt) 20W (Above 20W: 16.3%) 50W vs. 30W 10W to 30W From 5W, Mean 31.7 ± 3.0 N/A 20W to 40W Mean number of RF lesions 6.1 ± 4.8 vs. 16.8 ± 14.9 5.9 ± 6.6 vs. 7.6 ± 8.5 9 ± 5 vs. 7 ± 5 3.2 ± 1.1 5 ± 7 N/A Mean duration of RF delivery (seconds) 81.7 ± 53.5 vs. 85.4 ± 17.3 137 ± 191 vs. 218 ± 241 N/A N/A 222 ± 264 432 ± 384 (typical) vs. 318 ± 180 (atypical) Acute success (%) 98.5 98.8 vs. 97.7 96 98.7 98 N/A FU duration (months) 18.3 ± 4.1 39 ± 7.5 vs. 31 ± 11.4 N/A 28.1 ± 14.1 62 ± 43 3 Reablation or recurrence (%) 1.0 4.6 vs. 6.8 N/A 3.6 2.2 Transient AV block (%) 1.9 2.6 vs. 1.7 N/A 1.9 2 0.1 Permanent AV block (%) 0 0 vs. 0 2 0.2 0.2 0.1 AV, atrioventricular; FU, follow-up; N/A, not applicable; RF, radiofrequency. Transient anterograde AV block occurring during the procedure not only necessitates termination of the procedure but may also lead to a fatal complication requiring a permanent pacemaker if irreversible. It is expected that higher ablation energy and target temperature increase the incidence of transient AV block or VA block during junctional ectopy. 13 , 24 Therefore, it can be anticipated that fast-accelerated junctional rhythm and assessment of VA block during junctional ectopy with RF delivery at 20 W do not cause irreversible damage to the AV node. However, this may not hold true when higher power affects the fast pathway of AV node. In our study, transient AV block was observed in only 1.9% of cases, with most being second degree AV block (Mobitz type I), all of which resolved within 30 seconds. Analysis of the 16 patients in whom the procedure failed at 20 W revealed that they were generally younger and had a higher pre-ablation heart rate. Several factors may explain the failure of 20 W ablation in these patients. First, the high blood flow associated with a fast heart rate may have created a cooling effect, counteracting the ablation’s effectiveness. Second, rapid cardiac motion may have interfered with stable catheter contact. Third, 20 W ablation may not have generated sufficiently large lesions to achieve effective slow pathway modification. From our perspective, an acute success rate of 92.1% is acceptable, given the safety advantages of the low-power ablation, particularly the absence of permanent AV block requiring a pacemaker. Bortone et al previously demonstrated that low-power ablation of the slow pathway is not a new technique. 9 In their study, ablation power was progressively increased in 5 W increments every 5 seconds. Once slow-accelerated junctional rhythm was observed, the power was further increased by 10 W above the threshold for junctional rhythm appearance, with a total duration of 120 seconds. While this gradual power titration technique may be effective, it is challenging to implement in routine clinical practice unless performed by an experienced operator. In contrast, our approach is straightforward, requiring no special precautions beyond setting the power at a low level and checking the heart rate before ablation. Study limitations This study has several limitations. First, it is a relatively small-scale, non-randomized prospective study. Although all consenting patients with typical AVNRT were enrolled during the study period, selection bias may still be present. Additionally, the small sample size may have limited the statistical power to detect complications or recurrence. Given that the incidence of permanent AV block typically ranges from 0.1–0.8%, the sample size of 203 patients may be underpowered to definitively detect a difference in this rare outcome. Second, the optimal energy level may vary depending on catheter-tissue contact. In this study, all operators made efforts to ensure adequate catheter-tissue contact to achieve successful ablation with low energy. However, since a catheter capable of quantifying contact force was not used, variability among operators may exist. As a result, the required energy may differ depending on the degree of contact, and procedural outcomes may be influenced by the operator’s experience and expertise. Furthermore, because all ablation catheters used in this study were non-irrigated tip catheters, these findings may not be directly applicable to procedures performed with irrigated-tip catheters. Finally, the mean follow-up duration of 18.3 ± 4.1 months is sufficient to assess early outcomes but may be inadequate to capture very late recurrences of AVNRT. Moreover, the relatively short follow-up period limits the ability to detect late-onset AV block. Conclusion Atrioventricular nodal reentrant tachycardia, Catheter ablation, Radiofrequency ablation, Treatment outcome, Prospective studies Abbreviations AV atrioventricular AVNRT atrioventricular nodal reentrant tachycardia RF radiofrequency ToK triangle of Koch VA ventriculoatrial Declarations Author affiliations 1 Division of Cardiology, Jeonbuk National University Hospital and Jeonbuk National University Medical School, Jeonju, Korea 2 Division of Cardiology, Department of Internal Medicine, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Korea 3 Department of Cardiology, Konyang University Hospital, Daejeon, Korea 4 Cardiovascular Center, Seoul National University Bundang Hospital, Seongnam, Korea 5 Department of Cardiology in Internal Medicine, School of Medicine, Chungnam National University, Chungnam National University Sejong Hospital, Sejong, Korea Author contributions Lae-Young Jung, M.D. 1 , Chang Hee Kwon, M.D. 2 , In Geol Song, M.D. 3 , Ji Hyun Lee, M.D. 4 , Minsu Kim, M.D. 5 , M Kim and CH Kwon: substantial contributions to the conception or design of the work. M Kim and L-Y Jung: acquisition, analysis or interpretation of data for the work, drafting the manuscript. M Kim: revising it critically for important intellectual content and final approval of the version to be published as corresponding authors. CH Kwon, L-Y Jung, IG Song and JH Lee: data collection and agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved as coauthors Ac knowledgements This research was supported by Chungnam National University Sejong Hospital Research Fund, 2021 Disclosures None References Brugada J, Katritsis DG, Arbelo E, et al. 2019 ESC Guidelines for the management of patients with supraventricular tachycardiaThe Task Force for the management of patients with supraventricular tachycardia of the European Society of Cardiology (ESC). Eur Heart J . 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Ten year follow-up after radiofrequency catheter ablation for atrioventricular nodal reentrant tachycardia in the early days forever cured, or a source for new arrhythmias? Pacing Clin Electrophysiol . Dec 2005;28(12):1302-9. doi:10.1111/j.1540-8159.2005.00271.x Elhag O, Miller HC. Atrioventricular block occurring several months after radiofrequency ablation for the treatment of atrioventricular nodal re-entrant tachycardia. Heart . Jun 1998;79(6):616-8. doi:10.1136/hrt.79.6.616 Meininger GR, Calkins H. One method to reduce heart block risk during catheter ablation of atrioventricular nodal reentrant tachycardia. J Cardiovasc Electrophysiol . Jun 2004;15(6):727-8. doi:10.1046/j.1540-8167.2004.04095.x Liberman L, Hordof AJ, Pass RH. Rapid atrial pacing: a useful technique during slow pathway ablation. Pacing Clin Electrophysiol . Feb 2007;30(2):221-4. doi:10.1111/j.1540-8159.2007.00653.x Dechering DG, Schleberger R, Greiser E, et al. Outcome of slow pathway modulation for atrioventricular nodal reentrant tachycardia with 50 versus 30 watts—more power, more effect? Journal of Interventional Cardiac Electrophysiology . 2018;52:157-161. Katritsis DG, Zografos T, Siontis KC, et al. Endpoints for successful slow pathway catheter ablation in typical and atypical atrioventricular nodal re-entrant tachycardia: a contemporary, multicenter study. JACC: Clinical Electrophysiology . 2019;5(1):113-119. Dechering DG, Schleberger R, Greiser E, et al. Outcome of slow pathway modulation for atrioventricular nodal reentrant tachycardia with 50 versus 30 watts-more power, more effect? J Interv Card Electrophysiol . Jul 2018;52(2):157-161. doi:10.1007/s10840-018-0360-0 Additional Declarations No competing interests reported. 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While this general approach is widely adopted, there is no standardized protocol for the optimal energy delivery or endpoint definition, leading to variability in practice among operators. Studies have reported a wide range of energy levels, from 20W to 50W, with some utilizing gradual up-titration strategies.\u003csup\u003e\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eHowever, a study by Bortone et al. reported that slow-accelerated junctional rhythm occurred at an average of 18.5 W during slow pathway modification.\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e Additionally, recent study by Kawaji et al. using a near-field detection algorithm\u0026ndash;guided approach has shown that the slow pathway is relatively superficial, suggesting that ablation can be effectively performed with lower energy levels.\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e Despite these findings, data on low-energy ablation remain limited, with most studies conducted in a single center settings and involving only a small number of selected patients.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eThe present study evaluates slow pathway ablation using low power energy (20 W), demonstrating favorable clinical outcomes with a low risk of procedure-related permanent AV block.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy patients\u003c/h2\u003e\u003cp\u003eWe conducted a prospective multicenter trial at three tertiary referral hospitals between May 2017 and February 2022. A total of 203 patients undergoing slow pathway ablation for typical AVNRT with 20 W energy were enrolled. All patients provided informed consent before the electrophysiology study and catheter ablation procedure. The study protocol was reviewed and approved by the institutional review board of Chungnam National University Sejong Hospital (CNUH201906005006-HE002).\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eDefinition\u003c/h3\u003e\n\u003cp\u003eTypical AVNRT was defined by an atrial-His/His-atrial ratio\u0026thinsp;\u0026gt;\u0026thinsp;1 and a His-atrial interval\u0026thinsp;\u0026le;\u0026thinsp;70 msec.\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e The echo window was defined as the interval during programmed stimulation with 10 msec decrements, during which a single echo was observed in the post-ablation period. Transient AV block was defined as second-degree AV block (Mobitz type I or II) or third-degree AV block that fully resolved during the electrophysiology study. Recurrence was defined as documented supraventricular tachycardia on a 12-lead ECG, 24-hour Holter monitoring, portable ECG devices, or an electrophysiology study.\u003c/p\u003e\n\u003ch3\u003eElectrophysiology study and ablation\u003c/h3\u003e\n\u003cp\u003eRF pulses of up to 60 s were applied at optimal sites with a maximum temperature of 60\u0026deg;C.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e Electrophysiology studies were conducted in the fasting state after obtaining written informed consent. All patients discontinued antiarrhythmic medications for at least 5 half-lives. Conscious sedation with midazolam, propofol, and fentanyl was administered. Venous access was obtained through both groins, and multipolar catheters were placed in standard positions: the high right atrium, coronary sinus, right ventricular apex, and His bundle. Sustained typical AVNRT was induced in all patients using programmed atrial and ventricular stimulation at different cycle lengths, with isoproterenol infusion as needed.\u003c/p\u003e\u003cp\u003eSlow pathway ablation followed standard techniques\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e using three types of conventional 4-mm ablation catheters (Blazer\u0026reg;, Boston Scientific, Natick, MA, USA; EZ Steer\u0026reg;, Biosense Webster Inc. Irvine, CA, USA; Safire\u0026reg;, St. Jude Medical, Minnetonka, MN, USA). The ablation catheter was positioned in the posterior part of atrial septum, between the tricuspid annulus and coronary sinus ostium, until the atrial- to-ventricular electrogram ratio ranged from approximately 1:10 to 1:3, with a delay in the atrial electrogram relative to the His bundle recording. When multicomponent or low-amplitude high frequent potentials were identified, RF energy was applied for up to 20 seconds until a junctional rhythm with 1:1 retrograde ventriculoatrial (VA) conduction was observed. Once slow-accelerated junctional rhythm, defined by \u0026ge;\u0026thinsp;5 junctional beats with a mean cycle of \u0026gt;\u0026thinsp;350 msec,\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e indicated effective modification, and energy delivery was continued for up to 60 seconds. If fast-accelerated junctional rhythm (defined by \u0026ge;\u0026thinsp;5 junctional beats with a mean cycle length of \u0026le;\u0026thinsp;350 msec\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e) or VA block occurred during junctional ectopy,\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e RF application was immediately discontinued, and the ablation catheter was repositioned. Acute successful slow pathway ablation for AVNRT was defined as the non-inducibility of typical AVNRT, regardless of the presence of an AH jump or fewer than two echo beats, with or without isoproterenol administration. If slow-accelerated junctional rhythm was not observed or if typical AVNRT was re-induced after appropriate slow pathway ablation with 20 W, the procedure was considered as a failure of low power energy ablation. In such cases, patients underwent repeat ablation with 25 W or higher. Failed ablation for AVNRT was defined as termination of the procedure despite reproducible induction of tachycardia.\u003c/p\u003e\u003cp\u003eThe location of successful slow pathway ablation was categorized into three regions. The posterior region included sites along the tricuspid septal annulus extending to the most inferoposterior aspect of the interatrial septum, adjacent to the coronary sinus ostium. The anterior region was defined as sites where the ablation catheter was positioned near the His-bundle catheter along the tricuspid septal annulus. The mid-region was located between the posterior and anterior regions.\u003c/p\u003e\n\u003ch3\u003eStudy outcome\u003c/h3\u003e\n\u003cp\u003eThe primary efficacy endpoint was to assess the acute procedural success rate and recurrence rate following ablation. The safety endpoint evaluated the incidence of serious adverse events, particularly AV block, during the procedure and follow-up. An independent clinical events committee adjudicated procedure-related serious adverse events. Additionally, electrophysiological changes during the procedure were analyzed.\u003c/p\u003e\n\u003ch3\u003eFollow-up\u003c/h3\u003e\n\u003cp\u003eRoutine follow-up visits were scheduled at 1, 6, 12, 18, and, 24 months post-procedure. Patients were also instructed to contact our team if they experienced symptoms of tachycardia or bradycardia.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eContinuous variables are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation, while categorical variables are expressed as frequencies. Group differences were assessed using χ\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e test for categorical variables and Student's t-test for continuous variables. Statistical analysis was performed using commercially available software (SPSS 21 for Windows; SPSS Inc., Chicago, IL, USA).\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003eBaseline characteristics\u003c/h2\u003e\u003cp\u003eThe baseline clinical characteristics of the study patients are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The mean age of the 203 patients was 54.4\u0026thinsp;\u0026plusmn;\u0026thinsp;17.3 years, with 82 men and 121 women. Hypertension was present in 68 patients (33.5%), while diabetes was reported in 31 patients (15.3%).\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\u003eClinical characteristics of the study patients\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNumber of patients\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e203\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge (years)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e54.4\u0026thinsp;\u0026plusmn;\u0026thinsp;17.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFemale, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e121 (59.6%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHypertension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e68 (33.5%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDiabetes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e31 (15.3%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCoronary artery disease\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e12 (5.9%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eValvular heart disease\u003c/p\u003e\u003cp\u003eChronic lung disease\u003c/p\u003e\u003cp\u003eStroke\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e4 (2.0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"2\"\u003eValues are expressed as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation or n (%).\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eAblation procedures\u003c/h2\u003e\u003cp\u003eProcedural data are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Slow pathway ablation using 20 W was acutely successful in 170 of 203 patients (83.7%). The successful ablation sites were located in the posterior region in 83 cases, the mid-region in 72 cases, and the anterior region of the triangle of Koch (ToK) in 15 cases. The mean number of RF applications required to achieve slow-accelerated junctional rhythm was 6.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8 in the 20 W group and 16.8\u0026thinsp;\u0026plusmn;\u0026thinsp;14.9 in patients requiring higher energy.\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\u003eStudy outcomes\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAcute procedural outcomes\u003c/p\u003e\u003cp\u003eNumber of patients\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e203\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAblation energy\u003c/p\u003e\u003cp\u003eSuccess at the initial 20W\u003c/p\u003e\u003cp\u003eFailure at 20W, then success after increasing 25W\u003c/p\u003e\u003cp\u003eEnergy exceeding 25W\u003c/p\u003e\u003cp\u003eResult of ablation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e170 (83.7%)\u003c/p\u003e\u003cp\u003e17 (8.4%)\u003c/p\u003e\u003cp\u003e16 (7.9%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSlow pathway ablation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e87 (42.9%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSlow pathway modification\u003c/p\u003e\u003cp\u003eFailed ablation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e113 (55.6%)\u003c/p\u003e\u003cp\u003e3 (1.5%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTransient VA block during junctional ectopy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e48 (23.6%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTransient AV block (second- or third-degree AV block)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (1.9%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSecond degree (Mobitz type I)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3 (1.5%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eThird degree\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (0.5%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eLong term outcomes\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePermanent AV block (second- or third-degree AV block)\u003c/p\u003e\u003cp\u003eLate recurrence\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003cp\u003e2 (0.9%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"2\"\u003eAV, atrioventricular; VA, ventriculoatrial.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\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 between the group that succeeded at 20W and above 20W\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\u003eClinical characteristics\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e20W (n\u0026thinsp;=\u0026thinsp;170)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAbove 20W (n\u0026thinsp;=\u0026thinsp;33)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e56.4\u0026thinsp;\u0026plusmn;\u0026thinsp;16.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e43.8\u0026thinsp;\u0026plusmn;\u0026thinsp;17.1\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\u003eSex\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e67 (36.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e15 (45.5%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.517\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHypertension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e58 (34.1%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10 (30.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.671\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDiabetes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e31 (18.2%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\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\" colname=\"c1\"\u003e\u003cp\u003eCoronary artery disease\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e9 (5.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3 (9.1%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.397\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStroke\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (2.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.373\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003eProcedural characteristics\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAblation site\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.060\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAblation at the posterior region of the ToK, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e83 (48.8%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9 (27.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAblation at the mid-region of the ToK, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e72 (42.4%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18 (54.5%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAblation at the anterior region of ToK, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e15 (8.8%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6 (18.2%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean RF applications\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e16.8\u0026thinsp;\u0026plusmn;\u0026thinsp;14.9\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\" colname=\"c1\"\u003e\u003cp\u003eSession with obtained slow-accelerated junctional rhythm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.9\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.4\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\u003eProcedure duration (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e82.2\u0026thinsp;\u0026plusmn;\u0026thinsp;22.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e112.4\u0026thinsp;\u0026plusmn;\u0026thinsp;30.1\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\u003eFluoroscopic time (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e13.2\u0026thinsp;\u0026plusmn;\u0026thinsp;8.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e21.5\u0026thinsp;\u0026plusmn;\u0026thinsp;11.2\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\u003eHR before ablation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e77.3\u0026thinsp;\u0026plusmn;\u0026thinsp;10.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e84.8\u0026thinsp;\u0026plusmn;\u0026thinsp;11.8\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\u003eRF duration (sec)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e81.7\u0026thinsp;\u0026plusmn;\u0026thinsp;53.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e85.4\u0026thinsp;\u0026plusmn;\u0026thinsp;17.3\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\u003eTotal RF ablation number\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e16.8\u0026thinsp;\u0026plusmn;\u0026thinsp;14.9\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\" colname=\"c1\"\u003e\u003cp\u003eTotal RF ablation time (sec)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e221.3\u0026thinsp;\u0026plusmn;\u0026thinsp;140.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e496\u0026thinsp;\u0026plusmn;\u0026thinsp;442.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eValues are expressed as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation or n (%).\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eAV, atrioventricular; HR, heart rate; RF, radiofrequency; ToK, triangle of Koch.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eAmong 33 patients who failed ablation at 20 W, 17 (8.4%) achieved success with 25 W, while 16 (7.9%) required an energy level exceeding 25 W. In all cases, ablation was performed in the posterior or mid-region of ToK. Three patients (1.5%) ultimately failed slow pathway ablation. Compared to those successfully treated with 20 W, patients requiring higher power were significantly younger (43.8\u0026thinsp;\u0026plusmn;\u0026thinsp;17.1 vs 56.4\u0026thinsp;\u0026plusmn;\u0026thinsp;16.5 years, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and had a higher pre-ablation heart rate (84.8\u0026thinsp;\u0026plusmn;\u0026thinsp;11.8 vs 77.3\u0026thinsp;\u0026plusmn;\u0026thinsp;10.8 bpm, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e\u003cp\u003eVA block during junctional ectopy occurred in 48 patients (23.6%) during RF application. Transient anterograde AV block was observed in 4 patients (1.9%), including three cases of second-degree Mobitz type I blocks and one case of third-degree AV block. All transient AV blocks occurred either after the acceleration of slow-accelerated junctional rhythm or during VA block assessment, prompting immediate cessation of RF application. All cases were resolved completely before the end of the procedure. No patient developed a permanent AV block requiring pacemaker implantation.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eFollow-up observation\u003c/h2\u003e\u003cp\u003ePatients were followed for an average of 18.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.1 months. Among those who experienced transient AV block during the procedure, no recurrence of AV block was observed during follow-up, and no patients required permanent pacemaker implantation. AVNRT recurred in two patients (0.9%), both of whom underwent repeat ablation with 30 W at the ToK. No adverse effects were reported during the follow-up period.\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe findings of this study demonstrate that low-power RF application for slow pathway modification is both effective and safe in the patients with typical AVNRT. In this study, 83.7% of patients undergoing AVNRT ablation successfully completed the procedure using a low energy of 20 W. A younger age and a higher pre-ablation heart rate were associated with failure at 20 W. Over a mean follow-up of 18.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.1 months, no patients developed permanent AV block requiring pacemaker implantation and the recurrence rate following low-power ablation was 0.9%. Initiating the procedure with low energy, followed by higher energy application if needed, represents a safe and effective strategy compared to conventional approaches.\u003c/p\u003e\u003cp\u003eThe risk of permanent AV block is not limited to the immediate post-procedural period but can persist for months or even years. Previous studies have reported cases of very late-onset second- or third-degree AV block following catheter ablation for AVNRT.\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e Transient retrograde VA block during junctional rhythm or the development of fast-accelerated junctional rhythm are significant predictors of AV block in patients undergoing slow pathway ablation. Therefore, careful monitoring of these signs and discontinuing the procedure before permanent damage occurs are crucial for preventing irreversible AV block. In this study, 48 patients (23.6%) experienced transient VA block during the procedure; however, immediate cessation of energy delivery prevented progression to permanent AV block. Although the exact pathophysiologic mechanism remains unclear, it is speculated that assessing transient VA block during junctional ectopy and promptly stopping RF application at a low energy level of 20 W helped to minimize irreversible damage.\u003c/p\u003e\u003cp\u003ePrevious studies have proposed several strategies to minimize the risk of AV block, including transient discontinuation of RF energy upon the development of junctional rhythm and performing multiple ablations with progressively longer durations\u0026thinsp;\u0026le;\u0026thinsp;30 seconds.\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e Another technique, introduced by Liberman et al.,\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e suggested that rapid atrial pacing during ablation could help to ensure intact anterograde AV conduction. However, if junctional rhythm is slightly faster than the pacing cycle length, it may be difficult to identify in this setting. This could delay RF termination by a few seconds, increasing the risk of permanent AV block. Several studies have also explored the use of low-power ablation to reduce AV block risk.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e summarizes these previous findings along with the results of the present study. Dechering \u0026amp; Schleberger et al. compared high-power (50 W) and moderate-power (30 W) ablation, reporting similar acute success rates but a slightly higher recurrence in the moderate-power (30W) group.\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e Langberg et al. investigated a stepwise energy escalation approach, starting as low as 10 W and increasing up to 30 W, demonstrating that gradual power titration effectively eliminated the slow pathway while avoiding unnecessary high-power applications.\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e Bortone et al. also proposed a gradual power titration starting from low energy, which proved to be a safe and controlled approach.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e In the present study, we further validated the efficacy of an initial low-power ablation strategy (20 W), with stepwise escalation only when necessary. Among previous studies utilizing an up-titration strategy starting from low energy, junctional rhythm was found to be unstable at energy levels below 20 W. Therefore, 20 W was considered the minimum effective threshold, forming the basis for the initial ablation energy (20 W) in this study. This approach resulted in a high acute success rate (98.5%) and a low recurrence rate (0.9%), with no cases of permanent AV block.\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 studies evaluating energy power for slow pathway ablation\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJung \u0026amp; Kwon et al.\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDechering \u0026amp; Schleberger et al.\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eLangberg et al.\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eBortone et al.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eWasmer et al.\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eKatritsis et al.\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStudy type\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eProspective\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRandomized (50W vs. 30W)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eRandomized (Anterior vs. Posterior)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eRetrospective\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eRetrospective\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eProspective\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNumber\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e203 (170 in 20W, 33 in above 20W)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e634 (342 in 50W vs. 292 in 30W)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e50 (28 vs. 22)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e468\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2,101\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1,087\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEnergy power (watt)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e20W (Above 20W: 16.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50W vs. 30W\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10W to 30W\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eFrom 5W,\u003c/p\u003e\u003cp\u003eMean 31.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eN/A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e20W to 40W\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean number of RF lesions\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8 vs. 16.8\u0026thinsp;\u0026plusmn;\u0026thinsp;14.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.9\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6 vs. 7.6\u0026thinsp;\u0026plusmn;\u0026thinsp;8.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e9\u0026thinsp;\u0026plusmn;\u0026thinsp;5 vs. 7\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e5\u0026thinsp;\u0026plusmn;\u0026thinsp;7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eN/A\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean duration of RF delivery (seconds)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e81.7\u0026thinsp;\u0026plusmn;\u0026thinsp;53.5 vs. 85.4\u0026thinsp;\u0026plusmn;\u0026thinsp;17.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e137\u0026thinsp;\u0026plusmn;\u0026thinsp;191 vs. 218\u0026thinsp;\u0026plusmn;\u0026thinsp;241\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eN/A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eN/A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e222\u0026thinsp;\u0026plusmn;\u0026thinsp;264\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e432\u0026thinsp;\u0026plusmn;\u0026thinsp;384 (typical) vs. 318\u0026thinsp;\u0026plusmn;\u0026thinsp;180 (atypical)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAcute success (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e98.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e98.8 vs. 97.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e98.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eN/A\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFU duration (months)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e18.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e39\u0026thinsp;\u0026plusmn;\u0026thinsp;7.5 vs. 31\u0026thinsp;\u0026plusmn;\u0026thinsp;11.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eN/A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e28.1\u0026thinsp;\u0026plusmn;\u0026thinsp;14.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e62\u0026thinsp;\u0026plusmn;\u0026thinsp;43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eReablation or recurrence (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.6 vs. 6.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eN/A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTransient AV block (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.6 vs. 1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eN/A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePermanent AV block (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 vs. 0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003eAV, atrioventricular; FU, follow-up; N/A, not applicable; RF, radiofrequency.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eTransient anterograde AV block occurring during the procedure not only necessitates termination of the procedure but may also lead to a fatal complication requiring a permanent pacemaker if irreversible. It is expected that higher ablation energy and target temperature increase the incidence of transient AV block or VA block during junctional ectopy.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e Therefore, it can be anticipated that fast-accelerated junctional rhythm and assessment of VA block during junctional ectopy with RF delivery at 20 W do not cause irreversible damage to the AV node. However, this may not hold true when higher power affects the fast pathway of AV node. In our study, transient AV block was observed in only 1.9% of cases, with most being second degree AV block (Mobitz type I), all of which resolved within 30 seconds.\u003c/p\u003e\u003cp\u003eAnalysis of the 16 patients in whom the procedure failed at 20 W revealed that they were generally younger and had a higher pre-ablation heart rate. Several factors may explain the failure of 20 W ablation in these patients. First, the high blood flow associated with a fast heart rate may have created a cooling effect, counteracting the ablation\u0026rsquo;s effectiveness. Second, rapid cardiac motion may have interfered with stable catheter contact. Third, 20 W ablation may not have generated sufficiently large lesions to achieve effective slow pathway modification.\u003c/p\u003e\u003cp\u003eFrom our perspective, an acute success rate of 92.1% is acceptable, given the safety advantages of the low-power ablation, particularly the absence of permanent AV block requiring a pacemaker. Bortone et al previously demonstrated that low-power ablation of the slow pathway is not a new technique.\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e In their study, ablation power was progressively increased in 5 W increments every 5 seconds. Once slow-accelerated junctional rhythm was observed, the power was further increased by 10 W above the threshold for junctional rhythm appearance, with a total duration of 120 seconds. While this gradual power titration technique may be effective, it is challenging to implement in routine clinical practice unless performed by an experienced operator. In contrast, our approach is straightforward, requiring no special precautions beyond setting the power at a low level and checking the heart rate before ablation.\u003c/p\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003eStudy limitations\u003c/h2\u003e\u003cp\u003eThis study has several limitations. First, it is a relatively small-scale, non-randomized prospective study. Although all consenting patients with typical AVNRT were enrolled during the study period, selection bias may still be present. Additionally, the small sample size may have limited the statistical power to detect complications or recurrence. Given that the incidence of permanent AV block typically ranges from 0.1\u0026ndash;0.8%, the sample size of 203 patients may be underpowered to definitively detect a difference in this rare outcome. Second, the optimal energy level may vary depending on catheter-tissue contact. In this study, all operators made efforts to ensure adequate catheter-tissue contact to achieve successful ablation with low energy. However, since a catheter capable of quantifying contact force was not used, variability among operators may exist. As a result, the required energy may differ depending on the degree of contact, and procedural outcomes may be influenced by the operator\u0026rsquo;s experience and expertise. Furthermore, because all ablation catheters used in this study were non-irrigated tip catheters, these findings may not be directly applicable to procedures performed with irrigated-tip catheters. Finally, the mean follow-up duration of 18.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.1 months is sufficient to assess early outcomes but may be inadequate to capture very late recurrences of AVNRT. Moreover, the relatively short follow-up period limits the ability to detect late-onset AV block.\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eAtrioventricular nodal reentrant tachycardia, Catheter ablation, Radiofrequency ablation, Treatment outcome, Prospective studies\u003c/p\u003e\n"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eAV\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eatrioventricular\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eAVNRT\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eatrioventricular nodal reentrant tachycardia\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eRF\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eradiofrequency\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eToK\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003etriangle of Koch\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eVA\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eventriculoatrial\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor affiliations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eDivision of Cardiology, Jeonbuk National University Hospital and Jeonbuk National University Medical School, Jeonju, Korea\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e2\u003c/sup\u003eDivision of Cardiology, Department of Internal Medicine, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul,\u0026nbsp;Korea\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e3\u003c/sup\u003eDepartment of Cardiology, Konyang University Hospital, Daejeon, Korea\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e4\u003c/sup\u003eCardiovascular Center, Seoul National University Bundang Hospital, Seongnam, Korea\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e5\u003c/sup\u003eDepartment of Cardiology in Internal Medicine, School of Medicine, Chungnam National University, Chungnam National University Sejong Hospital, Sejong, Korea\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLae-Young Jung, M.D.\u003csup\u003e1\u003c/sup\u003e, Chang Hee Kwon, M.D.\u003csup\u003e2\u003c/sup\u003e, In Geol Song, M.D.\u003csup\u003e3\u003c/sup\u003e, Ji Hyun Lee, M.D.\u003csup\u003e4\u003c/sup\u003e, Minsu Kim, M.D.\u003csup\u003e5\u003c/sup\u003e,\u003c/p\u003e\n\u003cp\u003eM Kim and CH Kwon: substantial contributions to the conception or design of the work. M Kim and L-Y Jung: acquisition, analysis or interpretation of data for the work, drafting the manuscript. M Kim: revising it critically for important intellectual content and final approval of the version to be published as corresponding authors. CH Kwon, L-Y Jung, IG Song and JH Lee: data collection and agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved as coauthors\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAc\u003c/strong\u003e\u003cstrong\u003eknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was supported by Chungnam National University Sejong Hospital Research Fund, 2021\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDisclosures\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eBrugada J, Katritsis DG, Arbelo E, et al. 2019 ESC Guidelines for the management of patients with supraventricular tachycardiaThe Task Force for the management of patients with supraventricular tachycardia of the European Society of Cardiology (ESC). \u003cem\u003eEur Heart J\u003c/em\u003e. Feb 1 2020;41(5):655-720. doi:10.1093/eurheartj/ehz467\u003c/li\u003e\n \u003cli\u003eFeldman A, Voskoboinik A, Kumar S, et al. Predictors of acute and long-term success of slow pathway ablation for atrioventricular nodal reentrant tachycardia: a single center series of 1,419 consecutive patients. \u003cem\u003ePacing Clin Electrophysiol\u003c/em\u003e. Aug 2011;34(8):927-33. doi:10.1111/j.1540-8159.2011.03092.x\u003c/li\u003e\n \u003cli\u003eHanninen M, Yeung-Lai-Wah N, Massel D, et al. Cryoablation versus RF ablation for AVNRT: A meta-analysis and systematic review. \u003cem\u003eJ Cardiovasc Electrophysiol\u003c/em\u003e. Dec 2013;24(12):1354-60. doi:10.1111/jce.12247\u003c/li\u003e\n \u003cli\u003eWasmer K, Dechering DG, Kobe J, et al. Patients\u0026apos; and procedural characteristics of AV-block during slow pathway modulation for AVNRT-single center 10year experience. \u003cem\u003eInt J Cardiol\u003c/em\u003e. Oct 1 2017;244:158-162. doi:10.1016/j.ijcard.2017.06.043\u003c/li\u003e\n \u003cli\u003eLiao JN, Hu YF, Wu TJ, et al. Permanent pacemaker implantation for late atrioventricular block in patients receiving catheter ablation for atrioventricular nodal reentrant tachycardia. \u003cem\u003eAm J Cardiol\u003c/em\u003e. Feb 15 2013;111(4):569-73. doi:10.1016/j.amjcard.2012.11.003\u003c/li\u003e\n \u003cli\u003eWillems S, Shenasa H, Kottkamp H, et al. Temperature-controlled slow pathway ablation for treatment of atrioventricular nodal reentrant tachycardia using a combined anatomical and electrogram guided strategy. \u003cem\u003eEuropean heart journal\u003c/em\u003e. 1996;17(7):1092-1102.\u003c/li\u003e\n \u003cli\u003eStrickberger SA, Zivin A, Daoud EG, et al. Temperature and impedance monitoring during slow pathway ablation in patients with AV nodal reentrant tachycardia. \u003cem\u003eJournal of cardiovascular electrophysiology\u003c/em\u003e. 1996;7(4):295-300.\u003c/li\u003e\n \u003cli\u003eBortone A, Boveda S, Jandaud S, et al. Gradual power titration using radiofrequency energy: a safe method for slow-pathway ablation in the setting of atrioventricular nodal re-entrant tachycardia. \u003cem\u003eEuropace\u003c/em\u003e. 2009;11(2):178-183.\u003c/li\u003e\n \u003cli\u003eBortone A, Boveda S, Jandaud S, et al. Gradual power titration using radiofrequency energy: a safe method for slow-pathway ablation in the setting of atrioventricular nodal re-entrant tachycardia. \u003cem\u003eEuropace\u003c/em\u003e. Feb 2009;11(2):178-83. doi:10.1093/europace/eun333\u003c/li\u003e\n \u003cli\u003eKawaji T, Yamano S, Aizawa T, et al. Novel near-field detection algorithm\u0026ndash;guided slow pathway ablation in atrioventricular nodal reentrant tachycardia. \u003cem\u003eHeart Rhythm\u003c/em\u003e. 2024;21(8):1440-1442.\u003c/li\u003e\n \u003cli\u003eLangberg JJ, Leon A, Borganelli M, et al. A randomized, prospective comparison of anterior and posterior approaches to radiofrequency catheter ablation of atrioventricular nodal reentry tachycardia. \u003cem\u003eCirculation\u003c/em\u003e. 1993;87(5):1551-1556.\u003c/li\u003e\n \u003cli\u003eKatritsis DG, Josephson ME. Classification of electrophysiological types of atrioventricular nodal re-entrant tachycardia: a reappraisal. \u003cem\u003eEuropace\u003c/em\u003e. Sep 2013;15(9):1231-40. doi:10.1093/europace/eut100\u003c/li\u003e\n \u003cli\u003eStrickberger SA, Tokano T, Tse HF, et al. Target temperatures of 48 degrees C versus 60 degrees C during slow pathway ablation: a randomized comparison. \u003cem\u003eJ Cardiovasc Electrophysiol\u003c/em\u003e. Jun 1999;10(6):799-803. doi:10.1111/j.1540-8167.1999.tb00259.x\u003c/li\u003e\n \u003cli\u003eKalbfleisch SJ, Strickberger SA, Williamson B, et al. Randomized comparison of anatomic and electrogram mapping approaches to ablation of the slow pathway of atrioventricular node reentrant tachycardia. \u003cem\u003eJ Am Coll Cardiol\u003c/em\u003e. Mar 1 1994;23(3):716-23. doi:10.1016/0735-1097(94)90759-5\u003c/li\u003e\n \u003cli\u003eHintringer F, Hartikainen J, Davies DW, et al. Prediction of atrioventricular block during radiofrequency ablation of the slow pathway of the atrioventricular node. \u003cem\u003eCirculation\u003c/em\u003e. Dec 15 1995;92(12):3490-6. doi:10.1161/01.cir.92.12.3490\u003c/li\u003e\n \u003cli\u003eLipscomb KJ, Zaidi AM, Fitzpatrick AP, Lefroy D. Slow pathway modification for atrioventricular node re-entrant tachycardia: fast junctional tachycardia predicts adverse prognosis. \u003cem\u003eHeart\u003c/em\u003e. Jan 2001;85(1):44-7. doi:10.1136/heart.85.1.44\u003c/li\u003e\n \u003cli\u003eThakur RK, Klein GJ, Yee R, Stites HW. Junctional tachycardia: a useful marker during radiofrequency ablation for atrioventricular node reentrant tachycardia. \u003cem\u003eJ Am Coll Cardiol\u003c/em\u003e. Nov 15 1993;22(6):1706-10. doi:10.1016/0735-1097(93)90600-6\u003c/li\u003e\n \u003cli\u003eKimman GP, Bogaard MD, van Hemel NM, et al. Ten year follow-up after radiofrequency catheter ablation for atrioventricular nodal reentrant tachycardia in the early days forever cured, or a source for new arrhythmias? \u003cem\u003ePacing Clin Electrophysiol\u003c/em\u003e. Dec 2005;28(12):1302-9. doi:10.1111/j.1540-8159.2005.00271.x\u003c/li\u003e\n \u003cli\u003eElhag O, Miller HC. Atrioventricular block occurring several months after radiofrequency ablation for the treatment of atrioventricular nodal re-entrant tachycardia. \u003cem\u003eHeart\u003c/em\u003e. Jun 1998;79(6):616-8. doi:10.1136/hrt.79.6.616\u003c/li\u003e\n \u003cli\u003eMeininger GR, Calkins H. One method to reduce heart block risk during catheter ablation of atrioventricular nodal reentrant tachycardia. \u003cem\u003eJ Cardiovasc Electrophysiol\u003c/em\u003e. Jun 2004;15(6):727-8. doi:10.1046/j.1540-8167.2004.04095.x\u003c/li\u003e\n \u003cli\u003eLiberman L, Hordof AJ, Pass RH. Rapid atrial pacing: a useful technique during slow pathway ablation. \u003cem\u003ePacing Clin Electrophysiol\u003c/em\u003e. Feb 2007;30(2):221-4. doi:10.1111/j.1540-8159.2007.00653.x\u003c/li\u003e\n \u003cli\u003eDechering DG, Schleberger R, Greiser E, et al. Outcome of slow pathway modulation for atrioventricular nodal reentrant tachycardia with 50 versus 30 watts\u0026mdash;more power, more effect? \u003cem\u003eJournal of Interventional Cardiac Electrophysiology\u003c/em\u003e. 2018;52:157-161.\u003c/li\u003e\n \u003cli\u003eKatritsis DG, Zografos T, Siontis KC, et al. Endpoints for successful slow pathway catheter ablation in typical and atypical atrioventricular nodal re-entrant tachycardia: a contemporary, multicenter study. \u003cem\u003eJACC: Clinical Electrophysiology\u003c/em\u003e. 2019;5(1):113-119.\u003c/li\u003e\n \u003cli\u003eDechering DG, Schleberger R, Greiser E, et al. Outcome of slow pathway modulation for atrioventricular nodal reentrant tachycardia with 50 versus 30 watts-more power, more effect? \u003cem\u003eJ Interv Card Electrophysiol\u003c/em\u003e. Jul 2018;52(2):157-161. doi:10.1007/s10840-018-0360-0\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":"Atrioventricular nodal reentrant tachycardia, Catheter ablation, Radiofrequency ablation, Treatment outcome, Prospective studies","lastPublishedDoi":"10.21203/rs.3.rs-7444266/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7444266/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\u003eAtrioventricular nodal reentrant tachycardia (AVNRT) is the most common form of supraventricular tachycardia, and catheter ablation is a well-established treatment. However, the risk of atrioventricular (AV) block requiring permanent pacemaker implantation remains a significant concern, with reported incidence rates ranging from 0.1% to 0.8%.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eObjective\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study aimed to assess the clinical outcomes and safety of slow pathway ablation using low-power energy (20 W) for typical AVNRT.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis prospective multicenter trial enrolled 203 patients (mean age 54.4±17.3 years, 121 women) who underwent slow pathway ablation with 20 W between May 2017 and February 2022. Ablation was performed from the posterior region of the triangle of Koch until a slow-accelerated junctional rhythm was observed.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAmong the 203 patients who underwent ablation, 170 (83.7%) achieved successful ablation with 20 W. Of the 33 patients (16.3%) who did not achieve success with 20 W, 17 (8.4%) required 25 W, while 16 (7.9%) required an energy level greater than 25 W. A younger age (43.8±17.1 vs. 56.4±16.5 years, p\u0026lt;0.001) and a higher pre-ablation heart rate (84.8±11.8 vs. 77.3±10.8 bpm, p\u0026lt;0.001) were associated with failure at 20 W. Transient AV block occurred in 4 patients (1.9%). No patients developed permanent AV block requiring pacemaker implantation. The recurrence rate following low-power ablation was 0.9%. Over a mean follow-up of 18.3±4.1 months, no long-term complications were reported.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLow-power ablation using 20 W is a safe and effective strategy for typical AVNRT, with no cases of permanent AV block observed in this cohort.\u003c/p\u003e","manuscriptTitle":"Outcomes of Catheter Ablation for Typical Atrioventricular Nodal Reentrant Tachycardia with Low Power Energy of 20 W: A Prospective Multicenter Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-08 10:36:30","doi":"10.21203/rs.3.rs-7444266/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":"990004a9-9c2d-4a87-bd6a-751411505276","owner":[],"postedDate":"September 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-10-13T18:53:20+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-08 10:36:30","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7444266","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7444266","identity":"rs-7444266","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}