Background:Rhythm control of atrial fibrillation (AF) by pulmonary vein isolation alone is commonly difficult in this aging society, and the role of pharmacological therapy is being revisited. Identifying the lowest dose of amiodarone is important as this drug causes dose- and duration-related lung toxicity. Long-term safety of the use of extremely low-dose amiodarone in Japanese patients was retrospectively evaluated. Methods:Included were 120 patients treated with extremely low-dose amiodarone (50 mg daily) for persistent AF. KL-6 level was systematically measured at baseline and every 3 months thereafter. The patients were classified into a different quartiles (Q) based on the KL-6 level measured at baseline (Q1, Q2, Q3, and Q4). Thyroid function was also evaluated at each follow-up. Results:During a mean follow-up period of 51 months, KL-6 elevation (> 700 U/mL) occurred in 7 (5.8%) patients with higher baseline KL-6 (Q1, 0 patients; Q2, 0 patients; Q3, 1 patient; and Q4, 6 patients; p = 0.0018). Interstitial pneumonia (IP) was diagnosed in 1 (0.8%) patient in Q3 who recovered without the use of steroids. ROC curve analysis showed a cut-off value for KL-6 of 283 U/mL for predicting the subsequent elevation. Approximately 70% of the patients were free from recurrence of AF, although electrical cardioversion was required to restore sinus rhythm in 58 (48%) of them. Conclusions:Even an extremely low dose of amiodarone may potentially contribute to maintenance of sinus rhythm in highly selected patients with persistent AF. A low baseline KL-6 level may indicate patients at lower risk for amiodarone-related IP.

Background:Omnipolar mapping is an emerging technology with the potential to identify the critical conduction site in the cavotricuspid isthmus (CTI). Objective:This study aimed to elucidate the efficacy of omnipolar mapping-guided targeted ablation to create a CTI block. Methods:Patients who underwent a CTI block using radiofrequency applications (RFAs) were included. Omnipolar mapping was performed during CTI-dependent atrial flutter or pacing from the coronary sinus with a drive train (S1) and a single extra stimulus (S2), and 2 omnipolar maps were created: one with annotation of local potentials after S1 pacing (S1 map) and the other after S2 pacing (S2 map). RFAs were preferentially attempted at the atrial activation focusing sites (AAFSs) where atrial electrical excitation conducts centripetally toward those sites and centrifugally away from them in the omnipolar map. Results:50 patients were included. AAFSs were identified in 33 of 38 patients in whom an omnipolar map was created during sustained atrial flutter and in the S2 map in 11 of 12 patients in whom an omnipolar map was created during programmed pacing from the coronary sinus. No AAFS was identified in the S1 map. In the 44 patients in whom AAFSs were identified, a block line in the CTI was completed only by RFAs at the AAFSs, and a continuous linear ablation in the CTI was not necessary. Conclusion:An omnipolar mapping system can identify critical sites for a CTI block by visualizing AAFSs. The AAFSs might be preferable ablation targets in a targeted CTI block.

AbstractBackgroundThe Mt FUJI study was a multicenter, prospective, randomized, single‐blind, controlled trial comparing delivery catheter‐based and stylet‐based right ventricular (RV) lead placement at the RV septum. This study extended the follow‐up duration to 1 year after implantation.MethodsSeventy patients with pacemaker indications for atrioventricular block were randomly assigned to the delivery catheter and stylet groups. We compared the mid‐term efficacy and safety between the two groups at 1 year after implantation. The primary outcome was the change in the left ventricular ejection fraction (LVEF), and the secondary outcomes were changes in brain natriuretic peptide (BNP) levels, lead parameters, paced QRS duration, and the incidence of adverse events.ResultsAt the 1‐year follow‐up, no significant differences were observed in the changes in the LVEF (+1.0% ± 8.6% vs. +3.1% ± 8.1%, p = .332), BNP levels (+8.0 [−11.1, 26.5] pg/mL vs. −8.7 [−15.3, 13.2] pg/mL, p = .193), or lead performance between the delivery catheter and stylet groups. The QRS duration was significantly shorter in the delivery catheter group than in the stylet group (128 ± 23 ms vs. 146 ± 17 ms, p < .001). All‐cause death, hospitalization for heart failure, new development of atrial fibrillation, and pacing‐induced cardiomyopathy occurred in seven patients in the delivery catheter group and five in the stylet group.ConclusionThe delivery catheter system was similarly useful and safe compared to the stylet system in the mid‐term follow‐up from the Mt FUJI trial. Further long‐term evaluations are warranted.

Background:The epicardial connections (ECs) via intercaval fibres connecting the right-sided pulmonary veins (PVs) and right atrium (RA) can preclude isolation of the right-sided PVs. Such ECs occasionally have a unidirectional conduction property. Case summary:A 62-year-old man was referred to our institution for catheter ablation of paroxysmal atrial fibrillation (PAF). Circumferential antral PV isolation was performed via point-by-point radiofrequency (RF) applications. Thirty months after the ablation session, a recurrence of PAF was observed and a second procedure was performed. The right-sided PV was reconnected via an EC. Radiofrequency application at the RA insertion eliminated the EC. Thirty minutes thereafter, the right-sided PVs were reconnected. However, repetitive firings from the right-sided PVs did not conduct to the RA, indicating a unidirectional (RA to PV) reconnection of the EC, which was resolved by RF applications at the PV insertion. This time, the PV insertion of the EC was targeted and the unidirectional reconnection was successfully eliminated. The patient has remained free from any tachyarrhythmias for 3 years. Discussion:Although the mechanism of the unidirectional conduction property is unclear, source-sink mismatch and anisotropy are likely involved in the mechanism, as with accessory pathways. Electrophysiologists should be aware of the potential for unidirectional reconnection of ECs.

INTRODUCTION:The Mt. FUJI multicenter trial demonstrated that a delivery catheter system had a higher rate of successful right ventricular (RV) lead deployment on the RV septum (RVS) than a conventional stylet system. In this subanalysis of the Mt. FUJI trial, we assessed the differences in electrocardiogram (ECG) parameters during RV pacing between a delivery catheter system and a stylet system and their associations with the lead tip positions.METHODS:Among 70 patients enrolled in the Mt FUJI trial, ECG parameters, RV lead tip positions, and lead depth inside the septum assessed by computed tomography were compared between the catheter group (n = 36) and stylet group (n = 34).RESULTS:The paced QRS duration (QRS-d), corrected paced QT (QTc), and JT interval (JTc) were significantly shorter in the catheter group than in the stylet group (QRS-d: 130 ± 19 vs. 142 ± 15 ms, p = .004; QTc: 476 ± 25 vs. 514 ± 20 ms, p < .001; JTc: 347 ± 24 vs. 372 ± 17 ms, p < .001). This superiority of the catheter group was maintained in a subgroup analysis of patients with an RV lead tip position at the septum. The lead depth inside the septum was greater in the catheter group than in the stylet group, and there was a significant negative correlation between the paced QRS-d and the lead depth.CONCLUSION:Using a delivery catheter system carries more physiological depolarization and repolarization during RVS pacing and deeper screw penetration in the septum in comparison to conventional stylet system. The lead depth could have a more impact on the ECG parameters rather than the type of pacing lead.

Uncoupling of the endocardial bundles in the left atrium was suggested during modified posterior wall isolation. Although this fact may not be observed because of the possible bridging conduction by epicardial bundles in humans, partially failed transmural ablation in the atrial roof may have iatrogenically unveiled this fact.

INTRODUCTION:This study sought to elucidate the impact of vein of Marshall (VOM) chemical ablation on atrial fibrillation (AF) drivers by investigating the changes in CARTOFINDER mappings before and after VOM chemical ablation in patients with persistent AF. METHODS:This study included 23 consecutive patients undergoing catheter ablation for long-persistent AF (>18 months). VOM chemical ablation was performed following pulmonary vein isolation. CARTOFINDER and AF cycle length (AFCL) maps were created in the left atrium (LA) before and after VOM chemical ablation. The LA was divided into 8 segments, and the number of focal activation points with 6 or more repetitions was counted in each segment. RESULTS:The number of focal activation points was largest in the LA appendage (LAA). After VOM chemical ablation, the number of focal activation points in the LA decreased significantly (37 [interquartile range, IQR: 19-55] vs. 15 [IQR: 7-21], p < .001), and median AFCL was significantly prolonged (159 [147-168] vs. 164 [150-173] ms, p < .001). In the assessment of each segment, significant decreases in focal activation points were observed in the inferior, lateral, and anterior segments and LAA. Among the focal activation points disappearing after chemical ablation, the number in the non-ethanol-affected area was significantly larger than that in the affected area (13 [8-25] vs. 4 [1-10], p < .001). CONCLUSIONS:VOM chemical ablation decreases AF drivers detected by CARTOFINDER. Mechanisms other than direct myocardial damage are considered to contribute the attenuation of AF drivers.

Journal of Cardiovascular ElectrophysiologyVolume 35, Issue 2 p. 360-361 INVITED EDITORIAL Perimitral conduction time: Check it before creating an empirical mitral isthmus block Hideyuki Hasebe MD, PhD, Hideyuki Hasebe MD, PhD orcid.org/0000-0001-7802-8511 Division of Arrhythmology, Shizuoka Saiseikai General Hospital, Shizuoka, Japan Department of Cardiology, Institute of Medicine, University of Tsukuba, Tsukuba, JapanSearch for more papers by this authorKentaro Yoshida MD, PhD, Corresponding Author Kentaro Yoshida MD, PhD [email protected] orcid.org/0000-0002-6033-2053 Department of Cardiology, Institute of Medicine, University of Tsukuba, Tsukuba, Japan Department of Cardiology, Ibaraki Prefectural Central Hospital, Kasama, Japan Correspondence Kentaro Yoshida, MD, PhD, Department of Cardiology, Institute of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan. Email: [email protected]Search for more papers by this author Hideyuki Hasebe MD, PhD, Hideyuki Hasebe MD, PhD orcid.org/0000-0001-7802-8511 Division of Arrhythmology, Shizuoka Saiseikai General Hospital, Shizuoka, Japan Department of Cardiology, Institute of Medicine, University of Tsukuba, Tsukuba, JapanSearch for more papers by this authorKentaro Yoshida MD, PhD, Corresponding Author Kentaro Yoshida MD, PhD [email protected] orcid.org/0000-0002-6033-2053 Department of Cardiology, Institute of Medicine, University of Tsukuba, Tsukuba, Japan Department of Cardiology, Ibaraki Prefectural Central Hospital, Kasama, Japan Correspondence Kentaro Yoshida, MD, PhD, Department of Cardiology, Institute of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan. Email: [email protected]Search for more papers by this author First published: 17 January 2024 https://doi.org/10.1111/jce.16189 Disclosures: None. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. CONFLICT OF INTEREST STATEMENT The authors declare no conflict of interest. REFERENCES 1Maheshwari A, Shirai Y, Hyman MC, et al. Septal versus lateral mitral isthmus ablation for treatment of mitral annular flutter. JACC Clin Electrophysiol. 2019; 5: 1292-1299. 10.1016/j.jacep.2019.08.014 PubMedGoogle Scholar 2Lim MW, Kistler PM. Managing peri-mitral flutter. J Cardiovasc Electrophysiol. 2023; 34: 2145-2151. 10.1111/jce.15808 PubMedWeb of Science®Google Scholar 3Schneider R, Lauschke J, Tischer T, et al. Pulmonary vein triggers play an important role in the initiation of atrial flutter: initial results from the prospective randomized Atrial Fibrillation Ablation in Atrial Flutter (Triple A) trial. Heart Rhythm. 2015; 12: 865-871. 10.1016/j.hrthm.2015.01.040 PubMedWeb of Science®Google Scholar 4Lee WC, Fang HY, Chen HC, et al. Additional cavotricuspid isthmus block ablation may not improve the outcome of atrial fibrillation ablation. Pacing Clin Electrophysiol. 2019; 42: 1421-1428. 10.1111/pace.13799 PubMedWeb of Science®Google Scholar 5Verma A, Jiang C, Betts TR, et al. Approaches to catheter ablation for persistent atrial fibrillation. N Engl J Med. 2015; 372: 1812-1822. 10.1056/NEJMoa1408288 PubMedWeb of Science®Google Scholar 6Hamoud NS, Abrich VA, Shen WK, Mulpuru SK, Srivathsan K. Achieving durable mitral isthmus block: challenges, pitfalls, and methods of assessment. J Cardiovasc Electrophysiol. 2019; 30: 1679-1687. 10.1111/jce.14079 PubMedWeb of Science®Google Scholar 7Nakashima T, Pambrun T, Vlachos K, et al. Impact of vein of Marshall ethanol infusion on mitral isthmus block. Circ Arrhyt Electrophysiol. 2020; 13:e008884. 10.1161/CIRCEP.120.008884 CASPubMedWeb of Science®Google Scholar 8Valderrábano M, Peterson LE, Swarup V, et al. Effect of catheter ablation with vein of Marshall ethanol infusion vs catheter ablation alone on persistent atrial fibrillation: the VENUS randomized clinical trial. JAMA. 2020; 324: 1620-1628. 10.1001/jama.2020.16195 PubMedWeb of Science®Google Scholar 9Derval N, Duchateau J, Denis A, et al. Marshall bundle elimination, pulmonary vein isolation, and line completion for anatomical ablation of persistent atrial fibrillation (Marshall-PLAN): prospective, single-center study. Heart Rhythm. 2021; 18: 529-537. 10.1016/j.hrthm.2020.12.023 PubMedWeb of Science®Google Scholar 10Hara S, Miwa N, Kusa S, et al. Conduction time around the mitral valve annulus has the potential to rule out postablation perimitral atrial tachycardia. J Cardiovasc Electrophysiol. 2024; 35(2): 348-359. doi:10.1111/jce.16166 10.1111/jce.16166 PubMedGoogle Scholar Volume35, Issue2February 2024Pages 360-361 ReferencesRelatedInformation

A 22-year-old woman without structural heart disease underwent catheter ablation of frequent premature atrial contractions (PACs). Radiofrequency applications from both the right and left atrium were effective in suppressing or eliminating these PACs. The distance between the right atrial ablation site and the successful ablation site at the right-sided pulmonary venous carina measured 18 mm on the CARTO map, and no cardiac structure, i.e. the inter-atrial septum, was present between those sites. Taken together, the epicardial muscular fibers in the inter-atrial groove were considered to play a role as an arrhythmogenic source of this atrial tachyarrhythmia.

INTRODUCTION:Electrophysiological characteristics of epicardial connections (ECs) in atria and pulmonary veins (PVs) are unclear despite their important contributions to atrial fibrillation (AF). Unidirectional conduction associated with source-sink mismatch can occur in ECs due to their fine fibers with abrupt changes in orientation. We detailed the prevalence and electrophysiological characteristics of unidirectional conduction in the atria and investigated its association with the clinical manifestation of AF. METHODS:This study retrospectively reviewed electrophysiological studies and radiofrequency catheter ablation in 261 consecutive patients with AF. RESULTS:Unidirectional conduction was observed during ablation encircling the PVs in eight (3.1%) patients, and all occurred in the suspected (N = 4) or definitively (N = 4) recognized ECs. These ECs included three intercaval bundles, four septopulmonary bundles, and one Marshall bundle, and were first manifested in a second procedure in 6 (75%) patients. The unidirectional property was from PV to atrium (exit conduction) in all intercaval bundles and three septopulmonary bundles, and from atrium to PV (entrance conduction) in the remaining two bundles. Intercaval bundles acted as a limb of bi-atrial macro-reentrant tachycardia (50%, three of the six including previous cases). Ablation of the exit outside the PVs, including the right atrium, eliminated ECs in three (38%) patients. All patients remain free from arrhythmia recurrence after a mean 13-month follow-up. CONCLUSION:A unidirectional conduction property was closely associated with the EC, as estimated by histological findings. Recognition of this fact by electrophysiologists may help to clarify mechanisms for AF and atrial tachycardia and guide the creation of efficient and safe ablation lesion sets.

AimsAlthough the delivery catheter system for pacemaker-lead implantation is a new alternative to the stylet system, no randomized controlled trial has addressed the difference in right ventricular (RV) lead placement accuracy to the septum between the stylet and the delivery catheter systems. This multicentre prospective randomized controlled trial aimed to prove the efficacy of the delivery catheter system for accurate delivery of RV lead to the septum.Methods and resultsIn this trial, 70 patients (mean age 78 & PLUSMN; 11 years; 30 men) with pacemaker indications of atrioventricular block were randomized to the delivery catheter or the stylet groups. Right ventricular lead tip positions were assessed using cardiac computed tomography within 4 weeks of pacemaker implantation. Lead tip positions were classified into RV septum, anterior/posterior edge of the RV septal wall, and RV free wall. The primary endpoint was the success rate of RV lead tip placement to the RV septum.ResultsRight ventricular leads were implanted as per allocation in all patients. The delivery catheter group had higher success rate of RV lead deployment to the septum (78 vs. 50%; P = 0.024) and narrower paced QRS width (130 +/- 19 vs. 142 +/- 15 ms P = 0.004) than those in the stylet group. However, there was no significant difference in procedure time [91 (IQR 68-119) vs. 85 (59-118) min; P = 0.488] or the incidence of RV lead dislodgment (0 vs. 3%; P = 0.486).ConclusionThe delivery catheter system can achieve a higher success rate of RV lead placement to the RV septum and narrower paced QRS width than the stylet system.

Although glucose metabolism and atrial fibrillation (AF) have complex interrelationships, the impact of catheter ablation of AF on glucose status has not been well evaluated. Continuous glucose monitoring (CGM) with a FreeStyle Libre Pro (Abbott) was performed for 48 h pre-procedure, during the procedure, and for 72 h post-procedure in 58 non-diabetes mellitus (DM) patients with symptomatic AF and 20 patients with supraventricular or ventricular arrhythmias as a control group. All ablation procedures including pulmonary vein isolation were performed successfully. Glucose levels during procedures consistently increased in the AF and control groups (83.1 ± 16.1 to 110.0 ± 20.5 mg/dL and 83.3 ± 14.7 to 98.6 ± 16.3 mg/dL, respectively, P < 0.001 for both), and Δ glucose levels (max minus min/procedure) were greater in the AF group than control group (P < 0.001). There was a trend toward higher mean glucose levels at 72 h after the procedures compared with those before the procedures in both the AF and control groups (from 103.4 ± 15.6 to 106.1 ± 13.0 mg/dL, P = 0.063 and from 100.2 ± 17.1 to 102.9 ± 16.9 mg/dL, P = 0.052). An acute increase in glucose level at the time of early AF recurrence (N = 9, 15.5%) could be detected by simultaneous CGM and ECG monitoring (89.7 ± 18.0 to 108.3 ± 30.5 mg/dL, P = 0.001). In conclusion, although AF ablation caused a statistically significant increase in the glucose levels during the procedures, it did not result in a pathologically significant change after ablation in non-DM patients. Simultaneous post-procedure CGM and ECG monitoring alerted us to possible acute increases in glucose levels at the onset of AF recurrence.

Previous studies have suggested the presence of slow pathway (SP) variants connected to the right atrial (RA) inferolateral free wall along the tricuspid annulus.1 Because this variant is rare, details such as its electrophysiological characteristics or anatomical course have not been well studied. Further, there are no previous reports showing local electrograms of such SPs. We report a case of fast-slow atrioventricular nodal reentrant tachycardia (AVNRT) using a variant of an SP extending to the inferior RA.

Key Teaching Points•Left-sided Mahaim pathways are rare, and their electrophysiological and anatomical characteristics have not been well studied.•Electrophysiological study revealed that the mechanism of the tachycardia was antidromic atrioventricular reciprocating tachycardia using a left-sided Mahaim pathway.•Detailed mapping, including that inside the coronary sinus, revealed that the Mahaim pathway was considered as a short atrioventricular pathway connecting the left atrium to the left ventricular epicardium. •Left-sided Mahaim pathways are rare, and their electrophysiological and anatomical characteristics have not been well studied.•Electrophysiological study revealed that the mechanism of the tachycardia was antidromic atrioventricular reciprocating tachycardia using a left-sided Mahaim pathway.•Detailed mapping, including that inside the coronary sinus, revealed that the Mahaim pathway was considered as a short atrioventricular pathway connecting the left atrium to the left ventricular epicardium.

BACKGROUND:An epicardial connection (EC) between the right-sided pulmonary venous (RtPV) carina and right atrium (RA) may preclude PV isolation, but its electrophysiological role during atrial fibrillation (AF) remains unknown.Methods and Results: This prospective observational study included 98 consecutive patients undergoing catheter ablation for AF, subdivided into the EC group (n=17) and non-EC group (n=80) based on observation of RA posterior wall breakthrough during RtPV pacing. Mean left atrial (LA) dominant frequency (mean DFLA) was defined as the averaged DFs at the right and left PVs and LA appendage. The regional DF was higher in the EC group vs. the non-EC group except at the left PV antrum. The DF at the RA appendage (RAA) and mean DFLAwere equivocal (6.5±0.7 vs. 6.6±0.7 Hz) in the EC group, but the mean DFLAwas significantly higher than that at the RAA (5.8±0.6 vs. 6.1±0.5 Hz, P=0.001) in the non-EC group, suggesting an LA-to-RA DF gradient. A significant correlation of DF between the RtPV antrum and RAA was observed in the EC group (P<0.001, r=0.84) but not in the non-EC group.CONCLUSIONS:An electrophysiological link via interatrial ECs might attenuate the hierarchical nature of activation frequencies of AF, leading to advanced electrical remodeling of the atria.

The presence of an epicardial connection between the left-sided pulmonary vein and left atrium was suggested during catheter ablation of atrial fibrillation because of sustainable unidirectional entrance conduction after complete endocardial ablation, centrifugal breakout deep inside the pulmonary vein, and immediate elimination of the conduction by point ablation. (Level of Difficulty: Advanced.).