Thomas A. Boyle

BACKGROUND: The subcutaneous implantable cardioverter defibrillator (S-ICD) offers protection from sudden cardiac death without transvenous leads. Although contemporary techniques and programming have reduced inappropriate shocks, high rates persist in certain populations. The objective of this study was to evaluate the impact of a novel quantitative vector screening (QVS) protocol on the incidence of sensing-related complications and inappropriate shocks in patients undergoing S-ICD implantation. METHODS: We analyzed 223 consecutive patients who underwent S-ICD implantation at the Hospital of the University of Pennsylvania from December 2018 to July 2025. Traditional vector screening was used before 2023. In 2023, we implemented QVS, which incorporated quantitative sensing scores for each candidate and raised the threshold for S-ICD implantation. The primary end point was time to first inappropriate shock or under-sensed ventricular arrhythmia. Secondary outcomes included SMART Pass deactivation and need for device revision. Outcomes were reported as survival analyses. RESULTS: During preimplant screening, the QVS protocol reduced patient eligibility from 96% to 83%. The median follow-up after implant was 42 months (interquartile range, 48) in the traditional vector screening arm and 18 months (interquartile range, 15) in the QVS arm. The primary end point of time to first inappropriate shock or under-sensed ventricular arrhythmia was longer in the QVS arm (log-rank, P =0.02). There were 23 primary end point events among 145 patients in the traditional vector screening arm (5.2 per 100 patient-years [95% CI, 3.1–7.4]) and 2 primary end point events among 78 patients in the QVS arm (1.8 per 100 patient-years [95% CI, 0.01–4.38]). CONCLUSIONS: Implementation of a novel S-ICD screening protocol with stricter eligibility thresholds reduced sensing-related complications, particularly inappropriate shocks.

Background: Data related to electrophysiologic characteristics of atypical atrial flutter (AFL) following atrial fibrillation (AF) ablation and its prognostic value on repeat ablation success are limited.Methods: We studied consecutive patients who underwent a repeat left atrial (LA) ablation procedure for either recurrent AF or atypical AFL, at least 3 months after index AF ablation, between January 2012 and July 2019. The demographics, clinical history, procedural data, complications, and 1‐year arrhythmia‐free survival rates were recorded for each subject after the first repeat ablation.Results: A total of 336 patients were included in our study. Among these 336 patients, 102 underwent a repeat ablation procedure for atypical AFL and 234 underwent a repeat ablation procedure for recurrent AF. The mean age was 63.7 ± 10.7 years, and 72.6% of patients were men. The atypical AFL cohort had significantly higher LA diameters (4.6 vs. 4.4 cm, p = .04) and LA volume indices (LAVi; 85.1 vs. 75.4 ml/m², p = .03) compared to AF patients at repeat ablation. Atypical AFL patients were more likely to have had index radiofrequency (RF) ablation (as opposed to cryoballoon) than recurrent AF patients (98% vs. 81%, p = .01). Atypical AFLs were roof‐dependent in 35.6% and peri‐mitral in 23.8% of cases. Major complications at repeat ablation occurred in 0.9% of the total cohort. Arrhythmia‐free survival at one year was significantly higher in the recurrent atypical AFL compared to the recurrent AF cohort (75.5 vs. 65.0%, p = .04).Conclusion: In our series, roof‐dependent flutter is the most common form of atypical atrial flutter post AF ablation. Patients developing atypical AFL after index AF ablation have greater LA dimensions than patients with recurrent AF. The success rate of first repeat ablation is significantly higher among patients with recurrent atypical AFL as compared to recurrent AF after index AF ablation.