Outcomes of Subcutaneous Implantable Cardioverter Defibrillators in Patients Being Considered for Heart Transplantation: A Retrospective Cohort Study

INTRODUCTION: Subcutaneous implantable cardioverter defibrillators (S-ICD) are an alternative to transvenous devices (TV-ICD) in patients not requiring bradycardia pacing, resynchronization (CRT) or anti-tachycardia pacing (ATP). At our center, S-ICDs are often preferred in patients being considered for heart transplantation (HTx) without pacing/CRT/ATP needs, as their removal post-HTx avoids retained transvenous leads which can preclude MRI surveillance for graft rejection. We assessed outcomes of S-ICDs in this population. METHODS: We retrospectively reviewed 201 S-ICD implants at our center; July 2016 - March 2025. RESULTS: We identified 33 patients (22 male; age 46 ± 13 years) who, at time of S-ICD implant, had been referred for HTx evaluation or were referred at any time thereafter. Etiologies were nonischemic cardiomyopathy (n = 18), hypertrophic cardiomyopathy (n = 5), ischemic cardiomyopathy (n = 4), congenital heart disease (n = 4), and myocarditis (n = 2). Median follow-up was 296 days [IQR = 72-798]. Two patients died, both non-arrhythmic. Four patients received appropriate S-ICD therapies and three had inappropriate shocks due to P- or T-wave oversensing (TWOS) (n = 2), or a rapidly conducted atrial arrhythmia (n = 1). Three patients, all with hypertrophic cardiomyopathy, received transvenous device upgrades: one to CRT-P for disease progression, one to TV-ICD for ATP-terminable ventricular tachycardia and one to TV-ICD due to inappropriate shocks from TWOS. Thirteen patients underwent HTx at median 257 days [IQR = 130-453] post S-ICD; three of whom were bridged with HeartMate 3 LVADs. One LVAD patient needed S-ICD deactivation due to electromagnetic interference. There were no retained device components following HTx and S-ICD extraction. CONCLUSION: In selected pre-HTx patients, S-ICDs offer arrhythmic protection while avoiding retained leads post-HTx.