Introduction: Radiofrequency ablation (RFA) slow pathway modification for catheter ablation of AV nodal reentrant tachycardia (AVNRT) is traditionally performed using a 4mm, non-irrigated (NI) RF ablation catheter. Slow pathway modification using irrigated, contact-force sensing (ICFS) RFA catheters has been described in case reports, but outcomes have not been systematically evaluated. Methods: Acute procedural outcomes of 200 consecutive patients undergoing slow pathway modification for AVNRT were analyzed. An ICFS 3.5mm RFA catheter (ThermoCool SmartTouch STSF, Biosense Webster, Inc.) was utilized in 134 patients, and a 4mm NI RFA catheter (EZ Steer, Biosense Webster, Inc.) was utilized in 66 patients. Electroanatomic maps were retrospectively analyzed in a blinded fashion to determine proximity of ablation lesions to the His region. Results: Baseline characteristics of patients in both groups were similar. Total RF time was significantly lower in the ICFS group compared to the NI group (5.53±4.6 vs. 6.24±4.9 min, p=0.03). Median procedure time was similar in both groups, ICFS 108.0 (87.5-131.5) vs. NI 100.0 (85.0-125.0) min, p=0.2). Ablation was required in closer proximity to the His region in the NI group compared to the ICFS group (14.4 ± 5.9 mm vs, 16.7 ± 6.4 mm, respectively, p=0.01). AVNRT was rendered non-inducible in all patients, and there was no arrhythmia recurrence during follow-up in both groups. Catheter ablation was complicated by AV block in one patient in the NI group. Conclusion: Slow pathway modification for catheter ablation of AVNRT using an irrigated, contact-force sensing RFA catheter is feasible, safe, and may facilitate shorter duration ablation while avoiding ablation in close proximity to the His region.

Incident atrial fibrillation (AF) is common after cavotricuspid isthmus (CTI) dependent atrial flutter (AFL) ablation. Risk factors for development of AF post ablation are not well understood. To identify patients undergoing CTI ablation for AFL most likely to develop AF. We identified 114 patients without history of AF who underwent CTI AFL ablation. We evaluated baseline characteristics, electrophysiology study (EPS) data and echocardiographic data for incidence of AF within 3 years. Incident AF was identified in 46 patients (40%) during 600 + 405 days follow-up. Left atrial volume index (LAVI) was significantly greater in patients who developed AF compared to those that did not (37  12.2 ml/m2 vs 30  13.4 ml/m2, p=.004). EPS data was similar between groups. Area under the receiver operator characteristic curve based on the LAVI for prediction of AF was 0.7 (p = 0.004). Kaplan-Meier estimated incidence of AF was significantly greater in patients with LAVI ≥ 30 ml/m2 than LAVI < 30 ml/m2 (66% vs 27%, p=0.004). Risk of incident AF in patients with LAVI > 40 mL/m2 was similar to that of LAVI 30-40 ml/m2 (67% vs 63%, respectively, p=0.97). In multivariate analysis LAVI remained the sole independent predictor of incidence AF after CTI AFL ablation. LAVI ≥ 30 ml/m2 is associated with significantly increased risk of incident AF following CTI ablation for typical AFL. The utility of elevated LAVI for identifying patients that may benefit from intensified arrhythmia monitoring, or prophylactic AF ablation requires further evaluation.

Symphony to Leadless pacing – An Ode to JoyHassan Khan1, Larry A Chinitz1*1Leon H. Charney Division of Cardiology. New York University Langone Health. New York, NY, USA*Larry A Chinitz MD, FACC, FACP Benjamin and Coyle Family Professor of Medicine and Cardiac Electrophysiology Director, Cardiac Electrophysiology and the NYU Heart Rhythm CenterClinical Director, Leon H Charney Division of CardiologyNYU School of Medicine 212-263-7149 (O)[email protected] count, text: 1222 (excluding references) Number of tables/figures: 1COI; L.Chinitz- Speakers Honoraria; Medtronic,AbbottCoi; H. Khan- NoneLudwig van Beethoven’s 9th Symphony is regarded by many musicologists as one of the finest works in the history of music. It is notable for several reasons, particularly being the first example of a composer using voices, with words sung by a chorus and vocal soloist in the final movement. These words were adapted from the poem ”Ode to Joy”, written by Friedrich Schiller, and to date symbolize the celebration of music, making all who hear it feel better about life.Leadless pacing has also made a transformational effect on the lives of patients with bradyarrhythmias. Introduced to overcome the complications and adverse effects associated with conventional transvenous pacemakers, leadless pacing is observed to be safe, with a low risk of both short and long-term adverse events and high rates of successful implantation1, 2. To further the role of leadless pacing, the MARVEL (Micra Atrial TRacking Using a Ventricular AccELerometer) 23 prospective non-randomized multicenter clinical trial, tested the ability of an enhanced AV synchronous pacing algorithm utilizing the device’s three axis accelerometer, to attain mechanical sensing of atrial contractility. The MICRA AV TPS (Medtronic, MN) was released in 2020 with a ventricular pacing and atrial tracking mode (VDD), and achieved mechanical atrial sensing resulting in AV-synchronous pacing of >70% at rest in 95% participants (38 of the 40 with complete heart block) within the trial. Significant benefits to AV synchrony include avoidance of pacemaker syndrome, improvement of quality of life and as seen in these patients, improvement in left ventricle stroke volume and function3-5.The study observed that AV synchrony varied with physical activity and posture, with best results achieved at rest. Patient selection is crucial for optimal use of this algorithm as it is difficult to track atrial rates >105 bpm. At higher sinus rates, i.e. during exercise, the A3 and A4 signals fuse, along with encroachment of A4 on PVAB as the sinus rate increases further. Patient characteristics remain crucial and as seen in a subsidiary analysis of the MARVEL 2, individuals with markers of diastolic dysfunction (higher E/A ratios) and /or atrial myopathy (atrial strain) were found to be at higher risk of reduced mechanical atrial sensing of A46. Moreover, those with weak atrial contractions may not provide adequate A4 signals to the accelerometer. Therefore, performances of the algorithm in a real-world setting may not mirror those seen in the clinical trial arena. Further complicating the issue remains the ideal threshold for AV synchrony, which is assigned to >70% in research studies. In practice however, the AV synchrony cut-off required to achieve meaningful clinical benefit, avoid pacemaker syndrome and improve quality of life remains uncertain, though is certainly not 100%Recognizing that optimal AV synchrony in routine clinical practice may be challenging, Kowgli et al. in this issue of the Journal of Cardiovascular Electrophysiology , describe their multicenter institutional experience of outpatient programming optimization of the AV-synchronous MICRA leadless pacing system7. They included 43 patients with MICRA AV following exclusion of those with persistent atrial fibrillation or reduced follow-up. They describe the frequency of AV synchrony (defined as the ratio of atrial mechanically sensed (AM)-ventricular pacing to total ventricular paced percentage) at device interrogation done at 3 months of follow up. They report an overall mean AV synchronous pacing (AsVP) of 62.9%. In 65% of the patients adequate AV synchrony with AsVP >70% was found. Those with inadequate AsVP (<70%) had a higher body mass index, higher prevalence of congestive heart failure and prior history of cardiac surgery. Authors note that a small A4-wave amplitude, high ventricular pacing burden, and inadequate device reprogramming (over-use of auto A4 threshold, or lack of initiation of VDD mode at initialization) were main considerations for suboptimal AV synchronous pacing.Most importantly, their data confirms and is in line with recent reports,8, 9 that the success in achieving AV synchrony in a real-world setting may be lower than the MARVEL 2 clinical trial. The results also emphasize the importance of active programming changes which can significantly improve AV synchrony following an optimization post implantation. As identified in this report, MICRA AV optimization may require a learning curve, noted by an improvement in AsVP from 55% earlier, to 68% later in the study. Critical programming changes made by performing a manual atrial mechanical (MAM) test while disabling the features that automatically affect these, include adjusting the post ventricular atrial blanking (PVAB), A3/A4 windows and A3/A4 thresholds, and turning off the AV conduction mode (VVI +) in those with complete heart block and escape >40 bpm. The authors and others8, 9 have identified helpful examples of troubleshooting these interval timings and thresholds for optimizing AV synchrony, which an implanter must be familiar with in order to successfully manage patients with leadless AV synchronous devices. Critically, while performing a MAM test, a key prerequisite for successful interpretation of device tracings is the inclusion of an optimal ECG tracing. In cases where standard leads do not show a discernable P wave, the Lewis lead method can be helpful10. Several key steps towards successful optimization of AV synchrony are summarized in Figure 1.Kowgli et al. evaluated AV synchrony at device interrogation 3 months post implant whereas MARVEL 2 limited the analysis duration to about 30 minutes immediately after pacemaker optimization. This is a somewhat artificial setting and would be expected to be different from observations made at 3 months and longer periods of follow-up. Real world settings are also associated with changes in heart rate, patient movement, atrial or ventricular arrhythmias, as well as changes in lifestyle and medications. Therefore, an optimization session both at post-op (prior to discharge) and in the clinic at follow-up, with prior Holter monitoring and exercise testing in younger patients, may help detect AV dysynchrony earlier and allow recognition and correction of atrial mechanical under or oversensing.The current study acknowledges the complexity of leadless pacing and the need for optimization at follow-up to achieve higher levels of AV synchrony. It also reflects on patient selection being crucial to reap the full benefits of leadless technology. In patients with fast baseline sinus rates, in younger and physically active patients, or those who may have a greater reliance on AV synchrony at peak heart rates, this device may not be optimal. In addition, P wave amplitude, frequent atrial and ventricular arrhythmias, and sinus bradycardia will adversely affect the ability to achieve AV Synchrony. With appropriate patient selection, monitoring and best practices of device programming, leadless pacemakers will undoubtedly achieve clinically relevant AV synchrony. The true marvel of leadless technology can be seen as an impressive reduction in complication rates and better patient satisfaction compared to current transvenous devices. Further improvements in design, technology and best practices will deliver symphony to pacing and afford those who use it an experience that is safe and reminiscent of normal cardiovascular physiology.

Introduction: Left atrial posterior wall (LAPW) isolation is associated with favorable outcomes for catheter ablation of persistent atrial fibrillation (PEAF). Techniques for LAPW isolation include ablation at the periphery with or without high density ablation within the LAPW. The proportion of LA isolated by the lesion set also varies greatly. The optimal technique to achieve LAPW isolation is not clear. Objective: To assess impact of ablation lesion density within and dimensions of the LAPW isolation region on arrhythmia recurrence in catheter ablation of PEAF. Methods: LAPW lesion density and surface area relative to total LA surface area were calculated using electroanatomic maps of 110 consecutive patients undergoing LAPW isolation for PEAF (CARTO 3, Biosense Webster, Inc.). LAPW isolation was performed at the discretion of 5 experienced operators after voltage mapping. LAPW PV entrance and exit block were confirmed. Arrhythmia recurrence at two years was assessed by Kaplan-Meier analysis. Results: LAPW lesion density ranged from 0% - 99%. The proportion of LA surface area isolated ranged from 35% - 75%. There was no significant difference in arrhythmia-free survival stratified by median LAPW ablation density (31% vs. 27%, p=0.8) or median proportion of electrically-isolated LA surface area (31% vs. 27%, p=0.8%). Voltage map-guided LAPW isolation did not significantly decrease arrhythmia recurrence (29% vs. 28%, p=1). Conclusion: Neither the density of ablation within nor the dimensions of the LAPW isolated region predicted arrhythmia-free survival for catheter ablation of PEAF. Voltage map-guided LAPW isolation resulted in similar ablation efficacy regardless of LA scar burden.

Our article reported risk factors for ICD lead failure at our medical center, and we found an elevated risk of ICD lead failure in multiple lead ICD systems implanted via cephalic venous access.(1) Our analysis was prompted by recent literature related to durability of the Linox ICD lead (Biotronik, Inc., Berlin, Germany), and we found similar, elevated risk of ICD lead failure implanted in multiple lead systems via cephalic access in Linox and non-Linox ICD leads. Given the small number of total lead failures in the overall cohort (6 of 660), and the retrospective, single-center nature of our analysis, we reviewed prior Linox ICD lead durability manuscripts for evidence of increased risk of failure in multiple lead ICD systems implanted via cephalic venous access. While no prior manuscript evaluated this specific risk, we did find a trend towards increased risk of lead failure in cohorts with greater proportions of multiple lead systems, and greater proportions of systems implanted via cephalic access, however these variables were included in the analysis in a minority of prior studies.Dr. Maas and colleagues express surprise at the high failure rate when implanting multiple leads in our cohort. We would clarify that we reported ICD lead failure in 4 of the 304 patients in our cohort with multiple ICD leads, and that the frequency of lead failure in multiple lead ICD systems was not statistically significantly different compared to that of single lead ICD systems. In contrast, and surprisingly to us, 3 of 30 patients with multiple lead ICD systems implanted via cephalic access experienced ICD lead failure, and the frequency of ICD lead failure was significantly greater in this group compared to the remaining cohort in Kaplan-Meier survival analyses.Maas and colleagues question the reason for utilization of cephalic access in 18% of patients, hypothesize that suboptimal implantation technique may be responsible for the elevated lead failure rate, and request clarification of lead failure mechanism. We did not systematically collect rationale for venous access technique, and venous access techniques was at the discretion of the implanting physician. Of the 6 lead failures, 3 were related to lead noise, and 3 were related to rising pacing thresholds. Of the three lead failures amongst patients with multiple lead systems implanted via cephalic venous access, 2 were related to lead noise, and 1 was related to a rising pacing threshold. We believe that the lead noise may be related to insulation breach that may be predisposed by lead-lead interactions in the region of the cephalic vein. ICD leads were returned to the manufacturer on an ad hoc basis, and no specific feedback was received from manufacturers related to leads included in our analysis. All implanting physicians were experienced operators, and there were no significant differences in frequency of ICD lead failure by operator. We agree that implantation technique may play an important role in lead failure risk, and our analysis should prompt extra caution when implanting multiple leads via cephalic venous access.Citing the above limitations of our analysis, Dr Maas and colleagues state that it is “too early to abandon cephalic vein access, even for multiple lead systems.” They also review recent literature reporting favorable acute outcomes of ultrasound guided axillary venous access. We agree that our analysis paired with our literature review is best considered hypothesis generating, and we hope that our analysis encourages future studies to consider our findings when selecting variables of interest in ICD lead durability studies. We share Dr. Maas and colleagues’ favorable view of data supporting axillary venous access, particularly in combination with ultrasound guidance. As a result, given the available evidence of acceptable alternative techniques, our practice is to favor axillary venous access during implantation of multiple lead ICD systems, but we would not hesitate to implant via cephalic venous access in the appropriate clinical scenario.References1. Barbhaiya CR, Niazi O, Bostrom J et al. Early ICD lead failure in defibrillator systems with multiple leads via cephalic access. Journal of cardiovascular electrophysiology 2020;31:1462-1469.