We read with great interest the recent study by Rogers, et al. describing lesion formation with continuous versus intermittent radiofrequency ablation.1 The authors applied 50 (ex-vivo) or 10 (in-vivo) watts with either intermittent (15-seconds x4, 30-seconds x2, or 60-seconds x1) or continuous (1, 2, 3, or 5 minutes) radiofrequency applications and examined lesion size with each strategy. Continuous lesions resulted in significantly larger lesion size with possibly increased risk of steam pops at high power. In the ex-vivo model, they saw rapid lesion formation in the first minute of ablation with substantial drop-off in expansion of lesion size over time especially after 3 minutes (down to 0.35mm/min at 5 minutes), and suggest that there is only minimal incremental benefit of prolonging ablation lesion duration beyond 3 minutes in normal tissue.They have, however, appropriately recognized the limitation of their model which lacks significant fibrosis, limiting the generalizability of their findings to ablation in patients with scar. It is important to recognize that lesion formation in scar-related ventricular tachycardia (VT) is likely to differ dramatically compared to normal myocardial tissue. Barkargan, et al. have shown in an in-vivo porcine model of anterior myocardial infarction that lesion formation in normal versus scar tissue can be substantially different.2Specifically, ablation lesions in scar tissue were histologically quite heterogeneous, and connective tissue tended to be more resistant to thermal injury than normal myocardium.We have seen many cases where after identifying critical VT circuit components with activation and entrainment mapping, VT slowing and termination could only be achieved very late (4-5 minutes) into radiofrequency application, suggesting continued lesion expansion due to delayed effect of conductive heating in scar tissue can persist well beyond 3 minutes. Historical data from Nath, et al. have demonstrated that tissue temperature of >50°C must be reached in order to achieve nonreversible cellular damage.3 In the setting of dense scar, as in patients with healed myocardial infarction or dense basal septal scar in nonischemic cardiomyopathy, dynamics of tissue heating and lesion formation are likely quite different than in normal tissue. Especially in intramural substrates which are “protected” by dense subendocardial (or subepicardial if ablating from the epicardium) scar, ablation with very long (>3 minute) lesions may have a more pronounced effect than in normal tissue. While in our experience, steam pops seem to occur less frequently when ablating in dense scar- even with long, high power lesions, close monitoring of ablation parameters including catheter tip temperature and impedance remain necessary during ablation to assure continued safety to avoid char formation and steam pops.We enthusiastically applaud the authors for their valuable contribution to the literature. While chronic cardiomyopathy models are technically difficult to create and costly to maintain, additional studies examining lesion formation in dense scar would be extremely helpful to delineate optimal ablation strategies in patient with cardiomyopathy and difficult VT substrates. Our clinical experience with late VT termination and prevention of inducibility after 4-5 minute radiofrequency ablation lesions in areas of marked fibrosis would support such additional study.References:1. Rogers AJ, Borne RT, Ho G, Sauer WH, Wang PJ, Narayan SM, Zheng L, Nguyen DT. Continuous Ablation Improves Lesion Maturation Compared with Intermittent Ablation Strategies. J Cardiovasc Electrophysiol 2020.2. Barkagan M, Leshem E, Shapira-Daniels A, Sroubek J, Buxton AE, Saffitz JE, Anter E. Histopathological Characterization of Radiofrequency Ablation in Ventricular Scar Tissue. JACC Clin Electrophysiol 2019;5:920-931.3. Nath S, DiMarco JP, Gallop RG, McRury ID, Haines DE. Effects of dispersive electrode position and surface area on electrical parameters and temperature during radiofrequency catheter ablation. Am J Cardiol 1996;77:765-767.

Introduction: Brugada syndrome is associated with ventricular arrhythmia leading to sudden cardiac death. Risk stratification is challenging, as major arrhythmic events (MAE) are rare. We assessed the utility of drug challenge testing in Brugada syndrome by a systematic review and meta-analysis. Methods and results: We comprehensively searched the databases of MEDLINE and EMBASE from inception to May 2019. Included studies compared the incidence of MAE between spontaneous and drug challenge induced Type-1. Data were combined using the random-effects, generic inverse variance method, to calculate pooled incidence and odds ratio (OR). Mixed-effects Poisson regression was used to calculated incidence rate ratio (IRR). Eighteen studies from 2006 to 2018 were included (4,099 patients, mean follow-up 4.5 years). Pooled annual incidences of MAE in spontaneous, drug challenge induced (regardless of symptoms), asymptomatic drug challenge induced, and symptomatic drug challenge induced Type-1 were 23.8 (95% confidence interval [CI]: 19.8-27.8), 6.5 (95% CI: 3.9-9.1), 2.1 (95% CI: -0.3-4.4), and 19.6 (95% CI: 9.9-29.3) per 1,000 person-years respectively. The incidence of MAE between symptomatic drug challenge induced and asymptomatic spontaneous Type-1 was not statistically different (IRR=1.0, 95%CI: 0.6-1.7). The presence of ventricular tachyarrhythmia during drug challenge testing was a predictor of MAE (OR=3.73, 95% CI: 1.77-7.86, p=0.001). Conclusions: The incidence of MAE in drug challenge induced Type-1 in asymptomatic patients is low. The incidence of MAE between symptomatic drug challenge induced and asymptomatic spontaneous Type-1 was similar. Ventricular tachyarrhythmia during drug challenge testing could be a useful risk marker for MAE in Brugada syndrome.

Despite extreme and undeniable progress in the concept of implantable cardioverter defibrillator (ICD) therapy over the last 40 years, the endocardial lead is still the weakest link of the system. Many efforts have been taken to improve the construction and consequently the durability of the lead. Not all of them were successful and some of the lead models proved to be technically imperfect, resulting in formal recalls. Similarly, patient- and procedure-related factors may strongly affect the lead reliability. The implantation of cardiac electronic devices (CIED) is considered to be a quite common vascular intervention. Also, there are strongly established opinions of best procedural manners, including the most optimal methods of vascular access during the CIED implantations.In this issue of the Journal of Cardiovascular Electrophysiology, Barbhaiya et al. present an interesting retrospective analysis of 660 patients who underwent the ICD implantations in one center from 2011-2017. The goal of the study was to determine the risk factors for premature lead failure. Four implanted leads models were assessed: Biotronik Linox, Sprint Quattro, Durata and Endotak.The main findings include:The ICD lead implantation via cephalic access in multi-lead ICD systems may be a risk factor for premature ICD lead failure (p<0.001).The overall risk of premature ICD lead failure was similar for all the analyzed lead models.Concerns regarding the durability of Biotronik Linox were discussed and the study showed its equal reliability compared to the other leads.Neither age nor gender were the risk factors for premature lead failure.An optimal vascular access for the endocardial lead implantation was investigated in many studies.1-4 So far, cephalic vein cutdown (CVC) was considered to be the method of choice, with the lowest rate of possible complications.2,4,5 Meta-analysis performed by Benz et al. (30 000 patients, more than 50 000 leads) compared CVC and subclavian puncture (SP) and demonstrated lower risk of lead failure when CVC was adopted.2 Axillary vein puncture (AP), especially when ultrasonography-guided, is a feasible technique and significantly reduces the probability of subclavian crush syndrome.6-8 Unfortunately this method is not used by many operators. EHRA survey from 2013 showed that in more than 80% of participating centers, the preferred method for venous access was either CVC or SP.9 What is worth emphasizing, in the study of Barbhaiya et al., axillary access was most often used for lead insertion – 76.8% (61-88%, dependently on the lead model). This fact may potentially explain the main study finding. It is also consistent with the interesting results of the PAIDLESS study presented in the paper of Shaikh et al.3 They showed that experienced operators preferably choose subclavian and/or axillary access (62% of implants), whereas low-volume implanters generally use cephalic vein approach (63%). High-volume operators are also less likely to experience lead failure.An important issue to discuss is the number of leads inserted via cephalic vein. The routine practice, also applied by Barbhaiya and colleagues, includes the placing of atrial and right ventricular leads via cephalic access, if possible. Inserting one or two leads is usually not a problem. There are many inventive ways for doing this, described in literature. Some operators go even further – they use cephalic vein to implant all three leads of cardiac resynchronization therapy (CRT) systems with the success rate of 87.7% - 91.7%.10,11The question of long-term reliability of the leads implanted in such a way is still open. They are tightly packed in one small vessel and possible lead - lead interaction may contribute to their failure. Especially the ICD leads, by definition more complex and sensitive, are prone to damage in these circumstances.Another possible locus minoris resistentiae is the site of cephalic vein ligation after the lead insertion. The line between an adequate and too strong suture tightening is quite narrow. The effort to stop the bleeding from the vein may cause ligation-induced lead insulation damage. Recently, Kajiyama et al. proposed a novel technique for the ligation of the cephalic vein during a two-in-one insertion of the leads.12 It reduces hemorrhaging without decreasing the lead safety.The discussion about the benefits of different vascular access should include the potential disadvantages of future lead extraction, especially in the multi-lead systems. Inserting more than one lead via cephalic vein may determine more problematic transvenous lead extraction procedure (TLE). It may also necessitate the extraction of the functioning lead because of its periprocedural damage during the TLE of the initially targeted lead.The reliability of ICD leads is certainly the most important feature. During the last decades several lead models produced by different manufacturers were recalled because of their serious technical defects. Numerous concerns and divergent literature data regarding the durability of the Linox lead were the premise for the authors to conduct the discussed study. An important observation is that all analyzed lead models, including Linox, were similar in terms of performance (p=0.769).Young and physically active patients were traditionally believed to have a higher risk of lead damage because of the intensive mechanical interaction between the lead and anatomical structures of costoclavicular space. This observation was not confirmed by the authors of the commented paper.The study has several limitations and they are all listed by the authors. The lack of multivariate risk factors analysis is the most important drawback. It could not be performed due to the low overall event rate. All interesting study findings require validation and further investigation.As the ICD lead failure is still a serious problem, the study investigating possible risk factors is always of great importance. With all the limitations, the paper presented by Barbhaiya et al. may be an important guide in dealing with the vascular access during CIED implantations. It sheds new light on the dogma of superiority of cephalic access. What is particularly important in the study outcome and what I personally find a very strong recommendation – is the conclusion that the multiple lead systems should be avoided, if not indicated, especially when combined with cephalic venous access. One possible solution is to use cephalic vein for one lead only. Prospective randomized studies directly comparing axillary and cephalic access would be highly desirable in order to come closer to the idea of the best vascular approach for the endocardial lead implantation.1. Knight BP, Curlett K, Oral H, Pelosi F, Morady F, Strickberger SA. Clinical predictors of successful cephalic vein access for implantation of endocardial leads. J Interv Card Electrophysiol.2002;7(2):177-180.2. Benz AP, Vamos M, Erath JW, Hohnloser SH. Cephalic vs. subclavian lead implantation in cardiac implantable electronic devices: a systematic review and meta-analysis. Europace.2019;21(1):121-129.3. Shaikh ZA, Chung JA, Kersten DJ, et al. Differences in Approaches and Outcomes of Defibrillator Lead Implants Between High-Volume and Low-Volume Operators: Results From the Pacemaker and Implantable Defibrillator Leads Survival Study (”PAIDLESS”). J Invasive Cardiol. 2017;29(12):E184-E189.4. Chan NY, Kwong NP, Cheong AP. Venous access and long-term pacemaker lead failure: comparing contrast-guided axillary vein puncture with subclavian puncture and cephalic cutdown. Europace.2017;19(7):1193-1197.5. Gallik DM, Ben-Zur UM, Gross JN, Furman S. Lead fracture in cephalic versus subclavian approach with transvenous implantable cardioverter defibrillator systems. Pacing Clin Electrophysiol.1996;19(7):1089-1094.6. Belott P. How to access the axillary vein. Heart Rhythm.2006;3(3):366-369.7. Liccardo M, Nocerino P, Gaia S, Ciardiello C. Efficacy of ultrasound-guided axillary/subclavian venous approaches for pacemaker and defibrillator lead implantation: a randomized study. J Interv Card Electrophysiol. 2018;51(2):153-160.8. Squara F, Tomi J, Scarlatti D, Theodore G, Moceri P, Ferrari E. Self-taught axillary vein access without venography for pacemaker implantation: prospective randomized comparison with the cephalic vein access. Europace. 2017;19(12):2001-2006.9. Bongiorni MG, Proclemer A, Dobreanu D, et al. Preferred tools and techniques for implantation of cardiac electronic devices in Europe: results of the European Heart Rhythm Association survey.Europace. 2013;15(11):1664-1668.10. Vogler J, Geisler A, Gosau N, et al. Triple lead cephalic versus subclavian vein approach in cardiac resynchronization therapy device implantation. Sci Rep. 2018;8(1):17709.11. Hadjis A, Proietti R, Essebag V. Implantation of cardiac resynchronization therapy devices using three leads by cephalic vein dissection approach. Europace. 2017;19(9):1514-1520.12. Kajiyama T, Ueda M, Ishimura M, et al. A novel technique for ligation of the cephalic vein reduces hemorrhaging during a two-in-one insertion of dual cardiac device leads. Indian Pacing Electrophysiol J. 2018;18(4):152-154.

Editorial commentary for “Electrogram Morphology Discriminators in Implantable Cardioverter Defibrillators: a comparative evaluation”.

The pandemic caused by SARS-CoV-2 has affected communities throughout the world. The global nature of health care disparities is exacerbated by COVID-19. Patients in Low-and Middle-Income Countries have limited health care resources and marginal support for the evaluation and treatment of cardiac rhythm disorders. Heart Rhythm Societies and their members need to advocate for increased subsidies and assistance for these patients.

Introduction: The clinical efficacy and safety of hot balloon ablation (HBA) for treatment of persistent AF (PerAF) remain unclear. We aimed to evaluate the clinical efficacy and safety of HBA vs. cryoballoon ablation (CBA) as treatment for PerAF. Methods: Of 195 consecutive patients who underwent initial catheter ablation for PerAF (AF lasting >7 days but <12 months), 158 propensity score-matched (79 HBA and 79 CBA) patients were included in our study. All patients who underwent HBA received applications of energy to the upper posterior LA wall with a larger balloon in addition to single shots to each pulmonary vein (PV) ostium, whereas those who underwent CBA received simple single-shot applications. The electrically isolated surface area (ISA), including the PV antrum and part of the posterior LA wall, was assessed by high-resolution mapping. Results: Success of the PV isolation with balloon shots alone did not differ between HBA and CBA (81% vs. 85%; P = 0.52). The ISA was generally wide in both groups and significantly larger in the HBA group than in the CBA group (61 ± 16% vs. 51 ± 12%, P < 0.001). The incidence of procedure-related complications did not differ significantly (HBA 4% vs. CBA 1%; P = 0.62) nor did the arrhythmia recurrence rate (HBA 11% vs. CBA 18% at 18 months; P = 0.26). Conclusion: Despite the difference in protocols, HBA and CBA performed for PerAF appear comparable in terms of wide antral lesion creation, clinical efficacy, and safety.

Background: Atrial conduction velocity may represent atrial fibrillation (AF) substrate after pulmonary vein isolation (PVI). To elucidate the association between whole left atrial conduction velocity (LACV) and AF recurrence after PVI. Methods and Results: This observational study enrolled 279 patients who underwent PVI alone as an initial AF ablation procedure. After PVI, the left atrium was mapped with a 20-pole multielectrode in conjunction with the CARTO3 system during 100-ppm right atrial pacing. Left atrial conduction distance and conduction time were calculated from the start to the end of the propagation wave front in the left atrium. LACVs on the anterior and posterior routes were calculated as conduction distance divided by conduction time. Anterior and posterior LACVs were slower in patients with AF recurrence than in those without (anterior, 0.79 [0.71, 0.86] vs. 0.96 [0.90, 1.06], p < 0.001; posterior, 0.99 [0.89, 1.14] vs. 1.10 [1.00, 1.29], p < 0.001). AF recurrence was best predicted by anterior LACV with a cut-off value of 0.87 m/s (sensitivity 87%, specificity 81%, and predictive accuracy 84%). Multivariate analysis demonstrated that a slow anterior LACV < 0.87 m/s was an independent predictor of AF recurrence with an adjusted hazard ratio of 11.8 (6.36 – 22.0). Patients with anterior low-voltage areas demonstrated slower anterior LACV than those without low-voltage areas (0.89 [0.71, 1.00] vs. 0.94 [0.87, 1.05], p < 0.001). Conclusion: A slow LACV in the entire left atrium was an excellent predictor of AF recurrence after PVI, suggesting the necessity of additional ablations.

His bundle pacing (HBP) offers physiologic pacing by placing the pacing lead directly to the His bundle. We present a case in which a HBP lead, implanted at the fragile membranous septum, resulted in a persistent restrictive peri-membranous ventricular septal defect (VSD). This complication of HBP has not been reported before but brings new insights in the discussion regarding the optimal position of a pacing lead in the ventricular septum. The fragility of the membranous septum and low rate of spontaneous closure of membranous VSD, might favor lead placement in the muscular septum when aiming for physiologic pacing.

Introduction: Silent cerebral events (SCEs) are related to the potential thromboembolic risk in atrial fibrillation (AF) ablation. Peri-procedural uninterrupted oral anticoagulation (OAC) reportedly reduced the risk of SCEs, but the incidence still remains. Methods and Results: AF patients undergoing catheter ablation were eligible. All patients took non-vitamin K antagonist oral anticoagulants (NOACs, n=248) or vitamin K antagonist (VKA, n=37) for peri-procedural OAC (>4 weeks) without interruption during the procedure. Brain magnetic resonance imaging was performed within 2 days after the procedure to detect SCEs. Clinical characteristics and procedure-related parameters were compared between patients with and without SCEs. SCEs were detected in 66 patients (23.1%, SCE[+]) but were not detected in 219 patients (SCE[-]). Average age was higher in SCE[+] than in SCE[-] (66±10 years vs. 62±12 years, p<0.05). Persistent AF prevalence, CHADS2/CHA2DS2-VASc scores, serum NT-ProBNP levels, left-atrial dimension (LAD), and spontaneous echo contrast prevalence in transesophageal echocardiography significantly increased in SCE[+] vs. SCE[-]. SCE[+] had lower baseline activated clotting time (ACT) before heparin injection and longer time to reach optimal ACT (>300 sec) than SCE [-] (146±27 sec vs. 156±29 sec and 44±30 sec vs. 35±25 sec, p<0.05, respectively). In multivariate analysis, LAD, baseline ACT, and time to reach the optimal ACT were predictors for SCEs. The average values of the ACT parameters were significantly different among NOACs/VKA. Conclusion: LAD and intra-procedural ACT kinetics significantly affect SCEs during AF ablation. Different anticoagulants have different impacts on ACT during the procedure, which should be considered when estimating the risk of SCEs.

A global coronavirus (COVID-19) pandemic occurred at the start of 2020 and is already responsible for more than 74,000 deaths worldwide, just over 100 years after the influenza pandemic of 1918. At the center of the crisis is the highly infectious and deadly SARS-CoV-2, which has altered everything from individual daily lives to the global economy and our collective consciousness. Aside from the pulmonary manifestations of disease, there are likely to be several electrophysiologic (EP) sequelae of COVID-19 infection and its treatment, due to consequences of myocarditis and the use of QT-prolonging drugs. Most crucially, the surge in COVID-19 positive patients that have already overwhelmed the New York City hospital system requires conservation of hospital resources including personal protective equipment (PPE), reassignment of personnel, and reorganization of institutions, including the EP laboratory. In this proposal, we detail the specific protocol changes that our EP department has adopted during the COVID-19 pandemic, including performance of only urgent/emergent procedures, afterhours/7-day per week laboratory operation, single attending-only cases to preserve PPE, appropriate use of PPE, telemedicine and video chat follow-up appointments, and daily conferences to collectively manage the clinical and ethical dilemmas to come. We discuss also discuss how we perform EP procedures on presumed COVID positive and COVID tested positive patients in order to highlight issues that others in the EP community may soon face in their own institution as the virus continues to spread nationally and internationally.