A 65 year-old with history of prior ablations for regular narrow QRS short- RP tachycardia presented with recurrence of palpitations. An electrophysiological study showed long VA tachycardia with concentric atrial activation with a left ventricular origin extrastimulus delivered during His refractoriness, advancing the next ‘A’. A HRVPB can only reset an ORT if it ‘pulls in’ the local V at the ventricular insertion of an accessory pathway. As showcased in this case, erudite analysis of the pattern of perturbation of local ventricular electrograms is of paramount significance when interpreting responses to this maneuver. This concept when fortified with a heightened index of clinical suspicion for mitral annular block, anatomical knowledge of the pattern of LA-CS muscular connections, and pathway orientation, led to accurate electrophysiological diagnosis and management.

Introduction: Studies have shown an association between outcome in cardiac resynchronization therapy (CRT) and longer interventricular delay at the site of the left ventricular (LV) lead. Targeted LV lead placement at the latest electrically activated segment increases LV function further as compared with standard treatment. We aimed to determine reproducibility and repeatability of identifying latest electrically activated segment during mapping of all available CS branches in patients receiving CRT. Methods: We included 35 patients who underwent CRT implantation with protocolled mapping guided LV lead implantation aiming for the site of latest electrical activation. Three different doctors experienced in electrophysiology and implantation of CRT devices independently measured time interval from the local bipolar right ventricular (RV) electrogram (EGM) to the local unipolar LV EGM at all mapped sites (RV-LV). The segment with the latest electrical activation was defined as target segment (TS) and the CS tributary containing TS was defined as target vein (TV). Weighted Kappa statistics with 95% confidence intervals were computed to assess intra-and inter-observer agreement for TS and TV. Results: We mapped 258 segments within 131 veins. Weighted kappa values for repeatability were 0.85 (0.81-0.89) for TS and 0.92 (0.89-0.93) for TV, and weighted kappa values of inter-observer agreement ranged from 0.70 (0.61-0.73) to 0.80 (0.76-0.83) for TS and 0.73 (0.64-0.78) to 0.86 (0.83-0.89) for TV among all three observers. Conclusion: The reproducibility and repeatability of identifying latest electrically activated segment during mapping of all available CS branches in patients receiving CRT ranges from good to very good.

We introduce a fast and easy method of successfully grasping a lead without a free end called the “Wire ThRoUgh Snare Twice (Wire TRUST)” technique in a 49-year-old male patient who required transvenous lead extraction (TLE) and lead replacement due to lead malfunction. Our proposed technique is less difficult than using the Needle’s eye snare because the pigtail catheter is softer and has better operability. The Wire TRUST technique promptly allows a combined superior and femoral approach for TLE, even when the lead tip is difficult to free because of severe adhesion.

Background: Pulmonary vein isolation (PVI) has evolved to be an integral part of ablative therapy for atrial fibrillation (AF), however, recurrence rates of AF remain high even after complete wide area circumferential PVI. In recent years adjunct posterior wall isolation (PWI) has been performed in patients with more persistent forms of AF but the benefits remain unclear. Aim: The objective of this meta-analysis was to evaluate the efficacy of adjunct posterior wall isolation in reducing recurrence rate of AF using cryoballoon ablation (CBA). Methods: We searched PubMed, Google Scholar, Clinicaltrials.gov and Cochrane CENTRAL. We included studies comparing PVI to PVI + PWI in patients with persistent AF undergoing CBA. After data extraction and quality assessment of the studies, we assessed recurrence rates of atrial tachy-arrhythmias (AF, atrial flutter, and atrial tachycardia) as well as total ablation time and procedural adverse events. Risk ratio (RR), mean difference (MD) and 95% confidence interval (CI) were calculated using Review Manager. Results: Concomitant PWI demonstrated significant decrease in recurrence risk of AF (RR 0.48; 95% CI 0.36-0.64; p < 0.00001) as well as all atrial arrhythmias (RR 0.57; 95% CI 0.47-0.70; p < 0.0001). There was no significant difference in adverse events between both groups (RR 1.05; 95% CI 0.43-2.56; p = 0.91), whereas total ablation time was significantly increased in PVI + PWI group (MD 22.67, 95% CI, 7.61-37.73, p = 0.003). Conclusion: Adjunct PWI when compared to PVI alone decreases recurrence rates of atrial tachy-arrhythmias after CBA of persistent AF.

Background: Infection remains a major complication of cardiac implantable electronic devices (CIEDs) and can lead to significant morbidity and mortality. Extrathoracic devices that avoid epicardial or transvenous leads, such as the subcutaneous implantable cardioverter-defibrillator (S-ICD), can reduce the risk of serious infection-related complications, such as bloodstream infection and infective endocarditis. While the 2017 AHA/ACC/HRS guidelines include recommendations for S-ICD use for patients at high risk of infection, currently, there are no clinical trial data that address best practices for the prevention of S-ICD infections. Therefore, an expert panel was convened to develop consensus on these topics. Methods: An expert process mapping methodology was used to achieve consensus on the appropriate steps to minimize or prevent S-ICD infections. Two face-to-face meetings of high-volume S-ICD implanters and an infectious diseases specialist, with expertise on cardiovascular implantable electronic device infections, were conducted to develop consensus on useful strategies pre-, peri-, and post-implant to reduce S-ICD infection risk. Results: Expert panel consensus of recommended steps for patient preparation, S-ICD implantation, and post-operative management were developed to provide guidance in individual patient management. Conclusion: Achieving expert panel consensus by process mapping methodology for S-ICD infection prevention was attainable, and the results should be helpful to clinicians in adopting interventions to minimize risks of S-ICD infection.

Safety and Effect on Length of Stay of Intravenous Sotalol Initiation for Arrhythmia ManagementDiane H. Rizkallah, BS; Marwan M. Refaat, MDDivision of Cardiology, Department of Internal Medicine, American University of Beirut Medical Center, Beirut, LebanonRunning Title: Safety and Effect on LOS of IV SotalolWords: 598 (excluding the title page and references)Keywords: Heart Diseases, Cardiovascular Diseases, Cardiac Arrhythmias, Safety, Length of StayFunding: NoneDisclosures: NoneCorresponding Author:Marwan M. Refaat, MD, FACC, FAHA, FHRS, FRCPTenured Professor of MedicineTenured Professor of Biochemistry and Molecular GeneticsVan Dyck Medical Educator and Director of the Cardiovascular Fellowship ProgramDepartment of Internal Medicine, Cardiovascular Medicine/Cardiac ElectrophysiologyAmerican University of Beirut Faculty of Medicine and Medical CenterPO Box 11-0236, Riad El-Solh 1107 2020- Beirut, LebanonUS Address: 3 Dag Hammarskjold Plaza, 8th Floor, New York, NY 10017, USAOffice: +961-1-350000/+961-1-374374 Extension 5353 or Extension 5366 (Direct)Email: mr48@aub.edu.lbSotalol is a class III antiarrhythmic drug with beta-adrenergic blocking activity, used to manage both supraventricular and ventricular arrhythmias. It is available in both oral and intravenous formulations[1]. The FDA approved intravenous Sotalol in March 2020. Sotalol is known to cause QTc prolongation with serum sotalol concentration linearly correlating with QTc length regardless of the route of administration [2,3], with women being at higher risk than men[4]. QTc interval prolongation is one of many parameters that is associated with cardiovascular mortality [5]. QTc prolongation may lead to polymorphic ventricular tachycardia/Torsade de Pointes which is a potentially lethal condition that is acquired from medications or due to an underlying channelopathy predisposing to sudden cardiac arrest[6]. Additional adverse effects of sotalol may include hypotension, bradycardia and AV block[7,8]. Nevertheless, since its approval, IV sotalol has been successfully and safely used in both adult and pediatric patient populations for the management of arrhythmias in acute and chronic settings [9,10,11,12]. Initiation of sotalol therapy with PO loading requires 5 successive oral doses over a 3-day hospital stay for monitoring, at an estimated cost of $2931.55 per day [13]. In 2020, a protocol for IV loading of sotalol was developed using data modeling. This protocol was hypothesized to allow a significant reduction in the length of hospitalization, and thus in the incurred costs[14]. However, there has not been any large-scale implementation of this protocol, nor any comparison of its safety profile and efficacy to that of the traditional oral loading protocol.This study by Liu et al. is a nonrandomized clinical trial in which 29 patients underwent IV sotalol loading. They were compared by chart review to 20 patients who underwent PO sotalol loading in the same timeframe. The indication for sotalol initiation in both cases was for primary atrial or ventricular arrhythmias. The study’s main aim was to assess the safety profile of IV sotalol loading while comparing the length of hospitalization to that required for PO sotalol loading. The same exclusion and inclusion criteria were applied to both groups. Notably, patients with significantly depressed LVEF and creatinine clearance were excluded. The study revealed that safety outcomes were similar in both groups but that IV sotalol loading led to significantly shorter hospital stays. It also found that QT or QTc in patients receiving IV sotalol was similar at the conclusion of the one-hour infusion to that at discharge.These findings support the use of IV loading for sotalol initiation, as they suggest it requires shorter hospital stays than PO loading with similar safety profiles. As shorter hospital stays translate into lower patient days, lower costs, and these results suggest IV sotalol loading is more cost-efficient than its oral counterpart. They also suggest that the maximal increase in QT or QTc length following sotalol initiation is attained by the end of IV loading, thus indicating that patients may be discharged within less than 24 hours of drug initiation.While this study offered valuable insight, its design had significant limitations. Firstly, this was not a randomized clinical trial. A comparison of baseline characteristics between the two populations studied revealed a significantly higher proportion of females in the oral group, which may have inherently skewed outcomes related to QT and QTc length.Secondly, the sample size was small, with no long-term follow-up. Lastly, patients with significantly depressed GFR or LVEF, particularly prone to developing adverse effects with sotalol use, were excluded from the study. Randomized clinical trials examining the short-term and long-term safety of IV sotalol loading and the optimal length of hospitalization are needed, and such efforts are already underway.References:Batul, S. A., & Gopinathannair, R. (2017). Intravenous Sotalol - Reintroducing a Forgotten Agent to the Electrophysiology Therapeutic Arsenal. Journal of atrial fibrillation , 9 (5), 1499. https://doi.org/10.4022/jafib.1499Somberg, J. C., Preston, R. A., Ranade, V., & Molnar, J. (2010). QT prolongation and serum sotalol concentration are highly correlated following intravenous and oral sotalol. Cardiology , 116 (3), 219–225. https://doi.org/10.1159/000316050Barbey, J. T., Sale, M. E., Woosley, R. L., Shi, J., Melikian, A. P., & Hinderling, P. H. (1999). Pharmacokinetic, pharmacodynamic, and safety evaluation of an accelerated dose titration regimen of sotalol in healthy middle-aged subjects. Clinical pharmacology and therapeutics , 66 (1), 91–99. https://doi.org/10.1016/S0009-9236(99)70058-5Somberg, J. C., Preston, R. A., Ranade, V., Cvetanovic, I., & Molnar, J. (2012). Gender differences in cardiac repolarization following intravenous sotalol administration. Journal of cardiovascular pharmacology and therapeutics , 17 (1), 86–92. https://doi.org/10.1177/1074248411406505Al-Kindi SG, Refaat M, Jayyousi A, Asaad N, Al Suwaidi J, Abi Khalil C. Red Cell Distribution Width is Associated with All-Cause and Cardiovascular Mortality in Patients with Diabetes. Biomed Res Int 2017; 2017: 5843702Refaat MM, Hotait M, Tseng ZH: Utility of the Exercise Electrocardiogram Testing in Sudden Cardiac Death Risk Stratification.Ann Noninvasive Electrocardiol 2014; 19(4): 311-318.Marill, K. A., & Runge, T. (2001). Meta-analysis of the Risk of Torsades de Pointes in patients treated with intravenous racemic sotalol. Academic emergency medicine,  8 (2), 117–124. https://doi.org/10.1111/j.1553-2712.2001.tb01275.xMacNeil, D. J., Davies, R. O., & Deitchman, D. (1993). Clinical safety profile of sotalol in the treatment of arrhythmias. The American journal of cardiology , 72 (4), 44A–50A. https://doi.org/10.1016/0002-9149(93)90024-7Malloy-Walton, L. E., Von Bergen, N. H., Balaji, S., Fischbach, P. S., Garnreiter, J. M., Asaki, S. Y., Moak, J. P., Ochoa, L. A., Chang, P. M., Nguyen, H. H., Patel, A. R., Kirk, C., Sherman, A. K., Avari Silva, J. N., & Saul, J. P. (2022). IV Sotalol Use in Pediatric and Congenital Heart Patients: A Multicenter Registry Study. Journal of the American Heart Association , 11 (9), e024375. https://doi.org/10.1161/JAHA.121.024375Borquez, A. A., Aljohani, O. A., Williams, M. R., & Perry, J. C. (2020). Intravenous Sotalol in the Young: Safe and Effective Treatment With Standardized Protocols. JACC. Clinical electrophysiology , 6 (4), 425–432. https://doi.org/10.1016/j.jacep.2019.11.019Kerin, N. Z., & Jacob, S. (2011). The efficacy of sotalol in preventing postoperative atrial fibrillation: a meta-analysis. The American journal of medicine , 124 (9), 875.e1–875.e8759. https://doi.org/10.1016/j.amjmed.2011.04.025Milan, D. J., Saul, J. P., Somberg, J. C., & Molnar, J. (2017). Efficacy of Intravenous and Oral Sotalol in Pharmacologic Conversion of Atrial Fibrillation: A Systematic Review and Meta-Analysis. Cardiology , 136 (1), 52–60. https://doi.org/10.1159/000447237Varela, D. L., Burnham, T. S., T May, H., L Bair, T., Steinberg, B. A., B Muhlestein, J., L Anderson, J., U Knowlton, K., & Jared Bunch, T. (2022). Economics and outcomes of sotalol in-patient dosing approaches in patients with atrial fibrillation. Journal of cardiovascular electrophysiology , 33 (3), 333–342. https://doi.org/10.1111/jce.15342Somberg, J. C., Vinks, A. A., Dong, M., & Molnar, J. (2020). Model-Informed Development of Sotalol Loading and Dose Escalation Employing an Intravenous Infusion. Cardiology research , 11 (5), 294–304. https://doi.org/10.14740/cr1143

Title: Reply to “Pro-arrhythmia with Anti-arrhythmic Drugs in Patients with Idiopathic Ventricular Arrhythmia: A Common Problem with Vague Definitions and Complex Interactions”Jacky K. K. Tang MD1 and Marc W. Deyell MD MSC1,2Heart Rhythm Services, Division of Cardiology, University of British ColumbiaCentre for Cardiovascular Innovation, University of British ColumbiaWord Count: 538 (including references)Address for correspondence:Dr. Marc William DeyellHeart Rhythm Services, St. Paul’s Hospital200 – 1033 Davie St.Vancouver, B.C., Canada, V6E 1M7Phone: 604-806-8256; Fax: 604-806-8723Email: mdeyell@mail.ubc.ca@MarcDeyellCompeting Interests: Dr. Deyell reports research grants from Biosense Webster and honoraria from Biosense Webster, Medtronic and Abbott.Funding: This work was supported by the UBC Division of Cardiology Academic Practice Plan.Drs. Hasdemir and Payzin have cogently brought up one of the primary challenges in studying patients with frequent premature ventricular complexes (PVCs) and evaluating the impact of therapy. They highlight, based on their prior study,(1) that a group of patients may actually experience a significant increase in PVC burden (>50%) with medical therapy, which obviously raises concerns that this may enhance deleterious effects of PVCs, particularly in the long term.With the advent of ambulatory monitoring, it was recognized early that PVC burden could be highly variable, leading to measurement error when using a 24-hour monitor. This error is highest when performing before-and-after studies of the effect of intervention on PVC burden, using single monitoring periods of 24 hours prior to and after intervention. In particular, spontaneous reductions in PVC burden can overestimate treatment effects. This error can be minimized in two ways, through serial monitoring (repeated measures) or longer-term monitoring (>48h). Indeed, an elegant study by Dr. Mullis and colleagues, using 14 day patch monitors, showed a median absolute day-to-day fluctuation in PVC burden of almost 10% among patients with a high burden of PVC.(2) Thus, an apparent “pro-arrhythmic” effect of a medication may simply reflect inefficacy and expected variation in PVC burden.In our prior work,(3) published in this journal and referenced by Drs. Hasdemir and Payzin, we were also limited by using only 24-hour ambulatory monitors to assess PVC burden. However, we did include a control group on no medical therapy, to mitigate the effect of measurement error, by obtaining an estimate of variation in PVC burden in the absence of therapy. In our study, we observed a “pro-arrhythmic effect” (>50% increase in PVC burden), in 2.5% (1/40) of patients on no medical therapy, 7.5% (4/53) on beta blockers/calcium channel blockers and 11.1%% (3/27) on class I/III antiarrhythmic therapy. Despite the trend, these were not significantly different (p=0.28 and p=0.14 for beta blocker/calcium channel blocker and class I/III antiarrhythmics versus no therapy).This does not negate a potential pro-arrhythmic effect of medical therapy in a minority of patients. However, more definitive proof of a pro-arrhythmic effect, distinguishing this from spontaneous variation in PVC burden, would require demonstration of a decrease in PVC burden with cessation of therapy. This would best be accomplished with a blinded, cross-over trial design.Drs. Hasdemir and Payzin remind us to always critically assess, and reassess, our therapies for patients with frequent PVCs. We must always evaluate whether treatment is warranted (in the majority of cases it is not), and whether patients are at risk for adverse events, particularly from class I and III antiarrhythmics. Frequent PVCs make physicians uncomfortable but we should not rush to treatment and expose patients to unnecessary harm.References:1. Turan OE, Aydin M, Odabasi AY, Inc M, Payzin S, Hasdemir C. Therapeutic Inefficacy and Proarrhythmic Nature of Metoprolol Succinate and Carvedilol Therapy in Patients With Idiopathic, Frequent, Monomorphic Premature Ventricular Contractions. Am J Ther 2021;29:e34-e42.2. Mullis AH, Ayoub K, Shah J et al. Fluctuations in premature ventricular contraction burden can affect medical assessment and management. Heart Rhythm 2019;16:1570-1574.3. Tang JKK, Andrade JG, Hawkins NM et al. Effectiveness of medical therapy for treatment of idiopathic frequent premature ventricular complexes. Journal of Cardiovascular Electrophysiology 2021;32:2246-2253.

Leadless Pacing with Mechanical Atrial Sensing and Variable AV ConductionJason Cook, MDTravis D. Richardson, MDFrom Vanderbilt University Medical Center. Nashville, TennesseeCorresponding author:Travis D. Richardson, MDAssistant Professor Cardiac ElectrophysiologyVanderbilt Heart and Vascular Institute1215 21st Ave S. Nashville, TNMedical Center East, South Tower, Suite 5209ph (615) 936-7537fax (615) 936-5064travis.d.richardson@vanderbilt.eduWord Count:1331Disclosures: The authors report no relevant financial disclosures.Funding: NoneThe MicraTM leadless transcatheter pacing system (Medtronic Inc., Mounds View, MN) has been shown to be an effective alternative to transvenous pacing with excellent implantation success rates and durable long-term performance.1–3 The first generation device provided single chamber right ventricular pacing with rate responsiveness enabled by a 3-axis accelerometer.Recently, the MARVEL 2 study (Micra Atrial tRacking using a Ventricular accELerometer 2) reported the ability of software enhancements to allow a leadless pacemaker to deliver single chamber atrioventricular (AV) synchronized pacing.4 In contrast to dual-chamber transvenous pacemakers which sense atrial electrograms, the MARVEL 2 algorithm adjudicates atrial events using mechanically sensed atrial activity from the 3-axis accelerometer. During initial programming, the relative timing of mechanical events to the ventricular electrogram allows for identification of A3 (passive ventricular filling) and A4 (atrial contraction). Atrial-sensed events are then defined by the A4 signal, and tracking may occur. MARVEL 2 reported VDD pacing was achieved at rest in an impressive 89.2% of patients.The Micra AVTM system’s unique programming includes three basic pacing modes: VDD, VVI and VDIR (Figure 1). Additionally, two mode switch algorithms are available and by default programmed on: the AV conduction mode switch and the activity mode switch. Unlike mode switch algorithms in dual chamber pacing systems, which are intended to avoid inappropriate tracking of atrial arrhythmias, these algorithms are intended to 1) minimize ventricular pacing, and 2) to improve rate support during patient activity respectively.When the AV conduction mode switch algorithm is enabled, the device periodically switches from VDD to VVI at 40 bpm to allow for intrinsic AV conduction. If ventricular sensing occurs above a rate of 40 bpm, in order to reduce right ventricular pacing, VVI 40 programming will continue regardless of the programmed lower rate limit. However, if two of any window of four beats are paced at VVI 40, the device reverts to VDD. Thereafter, reassessments of AV conduction are performed at increasing intervals starting at 2 minutes until either AV conduction is detected or 8 hours is reached at which point subsequent testing occurs at regular 8 hour intervals.The activity mode switch algorithm utilizes the sensor indicated rate in an attempt to ensure adequate ventricular rate support during patient activity regardless of AV conduction. The sensor in the MicraTM is always running. If at any time 1) the sensor indicated rate is above the device programmed ADL rate, and 2) the current ventricular rate is >20 BPM below the sensor rate, the activity mode switch will change the device to VDIR mode with heart rates determined by the sensor. This switch may occur from either the VDD mode or VVI in the setting of AV conduction. The device will revert to VDD mode when the sensor rate drops below the ADL rate.With the added functionality of atrial sensing and the incorporation of the MARVEL 2 algorithms described above, in this issue of the Journal of Cardiovascular Electrophysiology, Garweg et al. examined the pacing behavior of the Micra AVTM in the presence of variable AV conduction, atrial arrhythmias, sinus bradycardia (< 40 bpm), sinus arrhythmia, and periods of atrial and ventricular ectopy (Reference). During the data collection period in MARVEL 2, ECG, electrogram, accelerometer waveforms, and device marker data were obtained; this was collected either after initial implant and follow-up or, for patients with previously placed devices, during a single encounter. The average monitoring period was 153 minutes. The study included 73 patients with normal sinus node function and varying degrees of AV block.While the number of patients with variable AV conduction was small (5), the investigators found that the rhythm checks allowed for appropriate mode adjustments during the study period. During periods of AV block, as expected, 99.9% ventricular pacing was observed while during 1:1 AV conduction only 0.2% pacing was observed. Ventricular pacing was monitored in patients with 1:1 AV conduction using conventional VVI pacing and MARVEL 2 programming. MARVEL 2 programming using the AV conduction mode switch algorithm resulted in a reduction in ventricular pacing from 22.8% to 0.2% (n=18). Reducing the burden of ventricular pacing is an important enhancement to the system with the potential to minimize pacing-induced cardiomyopathy.5One potential pitfall of atrial sensing addressed by this study is tracking of atrial arrhythmias. While the sample size was small (n=7), tracking of atrial fibrillation resulting in pacing at the upper tracking rate was not observed in any of the patients. In one patient with atrial flutter, intermittent atrial tracking did occur but did not result in tachycardia. In contrast to atrial rate based mode switching used in conventional dual-chamber pacemakers, the behavior of the MARVEL 2 algorithm during atrial fibrillation is dictated by the sensed ventricular rate. With the AV conduction mode switch enabled, if the ventricular rate is above 40 bpm, the pacing mode will be VVI at 40 bpm. If rates are less than 40 bpm, the pacing mode will be VDD. In the context of atrial fibrillation, reduced atrial contractility results in lack of mechanical sensing, and pacing at the lower rate is observed. In this small sample size, atrial arrhythmias did not result in device tracking resulting in tachycardia. Further investigation in a larger number of patients is warranted to better characterize these findings and to assess pacing behavior during more organized atrial arrhythmias which could result in mechanical sensing (atrial tachycardia and atrial flutter, for example).While the MARVEL 2 programming seems to perform well in the setting of atrial fibrillation or intermittent complete AV block, there are some potential pitfalls. AV conduction mode switch behavior is based on sensed ventricular rates with a threshold of 40 bpm; this cutoff is not currently programmable. Any ventricular sensed rhythm with a rate greater than 40 bpm will result in the device continuing at VVI 40. For example, in a patient with sinus rhythm at 90 bpm and 2:1 AV conduction, the device would not track the atrium and pace at 90 bpm, but rather remain VVI 40 because the ventricular sensed rate is above 40 bpm. The same would be observed in patients with junctional or ventricular escape rhythms >40 bpm. In this sense, pacing could be inappropriately inhibited during a potentially hemodynamically significant rhythm. For this reason, in our opinion, the AV conduction mode switch algorithm should be disabled in the majority of patients with AV block as this physiology is dynamic and sudden loss of rate support can have deleterious consequences. While the activity mode switch algorithm may address some of these concerns real world data are needed for validation.There is no question that the functionality and indications for leadless pacemakers will continue to expand. In current guidelines, which predate the development of the Micra AVTM, single chamber ventricular pacing is only recommended in patients with AV block and permanent atrial fibrillation, a low burden of anticipated pacing, or substantial comorbidities.6 Given the potential for lower complication rates compared with transvenous systems, Micra AV may be a superior option in some patients with complete heart block and preserved ventricular function. However, with the advent of conduction system pacing, the decreased risks of a leadless system have to be balanced with the relative risk of long term right ventricular pacing. Although the results will need to be validated with larger, longer-term studies, which are underway (Clinical trials.gov NCT04245345), these data indicate that Micra AVTM is likely to perform well in the setting of atrial arrhythmias. In patients with variable AV conduction, there are certainly pitfalls to the AV conduction mode switch algorithm, many of which could be avoided by the ability to program the mode switch VVI rate. While leadless pacing is often considered in patients with multiple comorbidities at high risk of complications from a transvenous system, we may be on the cusp of a dramatic paradigm shift. The technological developments and success of leadless pacing to date prompt the question of when, and not if, leadless dual chamber pacing and potentially even cardiac resynchronization will be available.References:1. Reynolds D, Duray GZ, Omar R, et al. A Leadless Intracardiac Transcatheter Pacing System. https://doi.org/10.1056/NEJMoa1511643. doi:10.1056/NEJMoa15116432. El-Chami MF, Al-Samadi F, Clementy N, et al. Updated performance of the Micra transcatheter pacemaker in the real-world setting: A comparison to the investigational study and a transvenous historical control. Heart Rhythm . 2018;15(12):1800-1807. doi:10.1016/j.hrthm.2018.08.0053. Duray GZ, Ritter P, El-Chami M, et al. Long-term performance of a transcatheter pacing system: 12-Month results from the Micra Transcatheter Pacing Study. Heart Rhythm . 2017;14(5):702-709. doi:10.1016/j.hrthm.2017.01.0354. Steinwender C, Khelae SK, Garweg C, et al. Atrioventricular Synchronous Pacing Using a Leadless Ventricular Pacemaker: Results From the MARVEL 2 Study. JACC Clin Electrophysiol . 2020;6(1):94-106. doi:10.1016/j.jacep.2019.10.0175. Merchant FM, Mittal S. Pacing induced cardiomyopathy. J Cardiovasc Electrophysiol . 2020;31(1):286-292. doi:10.1111/jce.142776. Kusumoto Fred M., Schoenfeld Mark H., Barrett Coletta, et al. 2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Circulation . 2019;140(8):e382-e482. doi:10.1161/CIR.0000000000000628

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Title: Making the Cut for Generator ReplacementsAuthors: Venkatesh Ravi, MD1; Jeremiah Wasserlauf, MD, MS1;1: Section of electrophysiology, Division of Cardiology, Department of Medicine, Rush University Medical Center, Chicago, USACorresponding author:Jeremiah Wasserlauf, MD, MSAssistant Professor of Medicine,Cardiac Electrophysiology, Department of Internal Medicine/Division of Cardiology,Rush University Medical Center.1717 W. Congress Parkway, Suite 345, Chicago, IL 60612Email: Jeremiah_wasserlauf@rush.eduFunding: NoneDisclosure: Dr. Jeremiah Wasserlauf has received consulting fees from Stryker. No other conflicts of interest to disclose.EditorialCardiac implantable electronic devices (CIED) have become a common treatment modality for cardiac arrhythmia with over 300,000 new implants every year in the United States. A growing number of patients will require device replacement procedures throughout their lifetime.1 In a registry of 1744 patients undergoing CIED replacement procedures, lead damage or dislodgement requiring revision was found to occur in 1% of patients without previously planned addition of leads.2 The resulting lead addition and extraction procedures give rise to added procedural time, risk of complications, prolonged hospitalization, and increased health care costs.2 Polyurethane and copolymer insulation materials are more susceptible to thermal damage when compared to silicone.3,4 Avoidance of lead damage during CIED replacement procedures has been a topic of increasing investigation, with studies evaluating differences between electrosurgical modes, power settings, blade orientation, and equipment manufacturers. Operators have the option to choose between standard electrocautery with non-insulated blades, and cautery with insulated blades (PEAK PlasmaBlade, Medtronic Inc., Minneapolis, MN, or Photonblade, Stryker, Kalamazoo, MI).Electrocautery operates by generating a high current density which results in resistive heating and thereby cuts or coagulates tissue. PlasmaBlade uses a proprietary power output waveform to deliver energy along the exposed edge of a thin, insulated electrode powered by a proprietary electrosurgical generator. Photonblade is an alternative insulated electrocautery blade that is compatible with a standard electrosurgical generator. In a retrospective study by Kypta et al, PlasmaBlade was associated with a lesser risk of lead damage and shorter procedure duration and hospital stay when compared with electrocautery and scissors.3 In an ex vivo animal tissue model using Photonblade, coagulation mode during cautery was associated with more damage than cut, and this effect was greatest when contact occurred using the active edge as opposed to the insulated flat side of the cautery blade, and when the lead insulation consisted of polyurethane or copolymer. Visible lead damage was found to be more common with PlasmaBlade when compared to Photonblade. 4In this edition of the Journal of Cardiovascular Electrophysiology , Ananwattanasuk et al performed a retrospective analysis of traditional electrocautery vs PlasmaBlade on lead parameters and complications following CIED generator replacement procedures.5 The study included 410 consecutive patients (840 leads) who underwent CIED replacement using conventional electrocautery (EC group) and 410 patients (824 leads) who underwent CIED replacement using PlasmaBlade (PK group). The power settings for the PK group were 6 in CUT mode and 8 in COAG mode. In the EC group, power output was set to 40 Watts for both CUT and COAG mode. CUT mode was used for tissue dissection and COAG was only used for hemostasis. The two groups had similar device systems and baseline characteristics. In comparison to the PK group, the EC group had a slightly lower proportion of silicone leads (78% vs 83%, p < 0.01) and a slightly higher proportion of polyurethane leads (19% vs 13%, p < 0.01). The study found no statistically significant difference in lead damage requiring lead revision between the EC group and PK group (0.6% vs 0.4%, p=0.5). There was no difference in procedural complications between the two groups (2.2% vs 1.2%, p = 0.28). There was no difference in lead sensing. There was a higher number of patients with a decrease in lead impedance in the PK group compared to the EC group (61.5% vs 52.1%, p < 0.01), and perhaps unexpectedly, more patients with an increase in lead impedance in the EC group compared to the PK group (46.8% vs 34.2%, p<0.01).On average, the change in pacing impedance changed less than 10% in both groups. A majority of leads in both groups were comprised of silicone which may have been a primary contributor to the low rate of lead damage observed. These findings contrast with the older retrospective study that found a lower risk of lead damage with PlasmaBlade compared to a historical control group where titanium scissors were used with conventional electrocautery for hemostasis. The difference observed in the prior study between groups, and the overall higher rates of lead damage in that study may have been related to the use of scissors or perhaps a greater proportion of leads with non-silicone insulation (lead insulation material was not reported). The present study by Ananwattanasuk et al contributes to the literature with a larger cohort of patients and contemporary operative technique.It is never too late to scrutinize the benefit of tools that have added costs as our procedural techniques evolve. The authors should be commended for rigorously collecting not only clinical outcomes but also electrical device parameters to assess for subclinical lead damage. Although generator replacements are short and less complex when compared to other EP procedures, the total cost of generator replacement procedures is estimated at several billion dollars yearly in the US alone.6 Leadless pacemakers and the evolution of modular systems are attractive and may solve some problems related to lead damage during generator replacements, or perhaps one day eliminate generator replacements altogether. However, with the current number of CIEDs in operation and the aging population, a growing number of patients will continue to require generator replacement procedures over the next several decades. The overall safety of generator replacement procedures has improved though advances such as avoidance of routine capsulectomy, antibiotic-impregnated pouches for appropriate candidates, and prolonged replacement intervals due to improved battery longevity. Through an unremitting focus on safety and cost-effectiveness, we will stay on the cutting edge of straightforward and complex procedures in the EP lab.References1. Greenspon AJ, Patel JD, Lau E, et al. 16-year trends in the infection burden for pacemakers and implantable cardioverter-defibrillators in the United States 1993 to 2008. J Am Coll Cardiol. 2011;58:1001-1006.2. Poole JE, Gleva MJ, Mela T, et al. Complication rates associated with pacemaker or implantable cardioverter-defibrillator generator replacements and upgrade procedures: results from the REPLACE registry.Circulation. 2010;122:1553-1561.3. Kypta A, Blessberger H, Saleh K, et al. An electrical plasma surgery tool for device replacement–retrospective evaluation of complications and economic evaluation of costs and resource use. Pacing Clin Electrophysiol. 2015;38:28-34.4. Wasserlauf J, Esheim T, Jarett NM, et al. Avoiding damage to transvenous leads-A comparison of electrocautery techniques and two insulated electrocautery blades. Pacing Clin Electrophysiol.2018;41:1593-1599.5. Ananwattanasuk T, Jame S, Bogun F, et al. Journal of Cardiovascular Electrophysiology. 2021.6. Hauser RG. The growing mismatch between patient longevity and the service life of implantable cardioverter-defibrillators. J Am Coll Cardiol. 2005;45:2022-2025.

Introduction: The advancement of artificial intelligence (AI) has aided clinicians in the interpretation of electrocardiograms (ECGs) serving as an essential tool to provide rapid triage and care. However, in some cases, AI can misinterpret an ECG and may mislead the interpreting physician. Therefore, we aimed to describe the rate of ECG misinterpretation and its potential clinical impact in patient’s management. Methods: We performed a retrospective descriptive analysis of misinterpreted ECGs and its clinical impact from May 28, 2020 to May 9, 2021. An electrophysiologist screened ECGs with confirmed diagnosis of atrial fibrillation (AF), sinus tachycardia (ST), sinus bradycardia (SB), intraventricular conduction delay (IVCD), and premature atrial contraction (PAC) that were performed in the emergency department. We then classified the misinterpreted ECGs as pseudo-AF, ST, SB, IVCD, or PAC into the correct diagnosis and reviewed the misinterpreted ECGs and medical records to evaluate inappropriate use of antiarrhythmic drugs (AAD), beta-blockers (BB), calcium channel blockers (CCB), anticoagulation, or resource utilization of cardiology and/or electrophysiology (EP) consultation. Results: A total of 4,969 ECGs were screened with diagnoses of AF (2,282), IVCD (296), PAC (972), SB (895), and ST (638). Among these, 101 ECGs (2.0%) were misinterpreted. Pseudo-AF (58.4%) was the most common followed by pseudo-PAC (14.9%), pseudo-ST (12.9%), pseudo-IVCD (7.9%) and pseudo-SB (6.0%). Patients with misinterpreted ECGs were aged 76.6±11.6yr with male (52.5%) predominance and hypertension being the most prevalent (83.2%) comorbid condition. The misinterpretation of ECGs led to the inappropriate use of BB (19.8%), CCB (5.0%), AAD therapy (7.9%), anticoagulation (6.9%) in patients with pseudo-AF, as well as inappropriate resource utilization including cardiology (41.6%) and EP (8.9%) consultations. Conclusions: Misinterpretation of ECGs may lead to inappropriate medical therapies and increased resource utilization. Therefore, it is essential to encourage physicians to carefully examine AI interpreted ECG’s, especially those interpreted as having AF.

Very High Power Short Duration Ablation: It Takes Two to Make a Thing Go Right? Samuel D. Maidman, M.D. & Chirag R. Barbhaiya, M.D.From the Leon H. Charney Division of Cardiology, NYU Grossman School of Medicine, NYU Langone Health, New York, New York, USA

Introduction: Novel ablation catheters equipped with mini-electrodes (ME) offer high resolution mapping for target tissue. This study aimed to evaluate the mapping performance and efficacy of ME catheters in radiofrequency ablation of paroxysmal supraventricular tachycardias (PSVTs). Methods: We prospectively enrolled 136 patients who were undergoing catheter ablation of PSVT including 76 patients with atrioventricular nodal reentrant tachycardia (AVNRT) and 60 patients with atrioventricular reentrant tachycardia (AVRT) or Wolff-Parkinson-White (WPW) syndrome. Patients were randomized to the ME group (ablation using a 4.5mm tip ME catheter) or the control group (ablation using a conventional 4mm tip catheter). The number of ablation attempt and cumulative ablation time to ablation endpoints, which was defined as an emergence of junctional rhythm in AVNRT or accessory pathway (AP) block in AVRT/WPW syndrome were compared. Results: During ablation procedures, discrete SP or AP electrograms were found in 27 (39.7%) patients in the ME group and 13 (19.1%) patients in the control group. The primary study outcomes were significantly lower in the ME group (ablation attempt number: 2.0 [1–4] vs. 3.0 [2–7] in the ME and control group, p=0.032; ablation time: 23.5 [5.0–111.5] vs. 64.5 [16.0–185.0] seconds, p=0.013). According to the PSVT diagnosis, ablation time to junctional rhythm was significantly shorter in the ME group in AVNRT. In AVRT/WPW syndrome, both ablation attempt number and ablation time to AP block showed trends favoring the ME group. Conclusion: The novel ME catheter was advantageous for identifying pathway potentials and reducing initial ablation attempt number and time in PSVT ablation. (ClinicalTrials.gov number, NCT04215640)

Catheter ablation for treatment of symptomatic non-paroxysmal atrial fibrillation remains challenging. Clinical failure and need for continued medical therapy or repeat ablation is common, especially in more advanced forms of atrial fibrillation. Hybrid ablation has emerged as a more effective and safe therapy than endocardial-only ablation particularly for longstanding persistent atrial fibrillation as demonstrated by the randomized controlled CONVERGE trial. Hybrid ablation requires collaboration of electrophysiologists and cardiac surgeons to develop specific workflows. This review describes the Hybrid Convergent approach in the context of available ablation options and offers guidance for workflow development and patient selection.

Dealing with RV-oversensing; separate sensitivity settings for brady and tachy sensingPranav Bhagirath MD PhD1, Kyle Beunder BSc1, Vokko van Halm MD PhD11Department of Cardiology, Amsterdam University Medical Center, Amsterdam, the NetherlandsFunding: (None)Disclosures: (None)

Catheter ablation of atrial fibrillation (AF) in patients with heart failure associated with a reduced EF (HFrEF) was associated with a significantly lower rate of a composite endpoint of death from any cause or hospitalization for worsening heart failure (HF) than medical therapy in the CASTLE-AF trial. In patients with HF and also with a preserved EF (HFpEF), AF is known to be associated with increased mortality. Although the particular benefit in patients with an EF >35% may suggest the need for prospective randomized control trial data in patients with HF to assess the role of ablation as a first-line therapy as Sessions AJ, et al. stated, we believe at present that 1) whether there is structural heart disease detected by cardiac images and 2) whether the left atrial voltage is generally low, should be assessed “before ablation” in each patient with HF to achieve a successful ablation.

We present a case report of severed epicardial atrial lead salvage using an IS-1 lead extender. A 37-year-old male with single ventricle physiology, Fontan palliation, sinus node dysfunction, recurrent atrial tachycardias and atrial fibrillation resulting in failing Fontan physiology presented with failure of the atrial pacing lead. The patient was initially paced with an epicardial system that had to be removed due to pocket infection, and the epicardial leads were cut and abandoned. Given his significant sinus node dysfunction he required atrial pacing to allow for rhythm control. The failing Fontan physiology of the patient precluded him from undergoing surgery for epicardial lead placement or a complex intravascular lead placement procedure (although anatomically feasible). We considered the option of salvaging the existing epicardial atrial leads to provide atrial pacing, allowing for rhythm control and improvement of his failing Fontan physiology as a bridge to a more permanent pacing solution. This case report is important because it demonstrates how a lead extender can be used to salvage a severed pacemaker lead. This may be useful for patients in whom implantation of new leads is not promptly feasible due to patient anatomy and/or clinical status.

Is Otsu Thresholding the Answer to Reproducible Quantification of Left Atrial Scar from Late Gadolinium-Enhancement MRI?Suvai Gunasekaran, PhDa, Daniel Kim, PhDa,ba Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, IL, United Statesb Department of Biomedical Engineering, Northwestern University, Evanston, IL, United StatesPlease send correspondence to:Daniel Kim, PhDDepartment of RadiologyNorthwestern University737 N. Michigan Avenue Suite 1600Chicago, IL 60611 daniel.kim3@northwestern.edu O:312.926.1733 F:312.926.5991