1Universitätsklinikum Münster Klinik für Kardiologie II - Rhythmologie Münster, Deutschland
Background: The totally subcutaneous implantable defibrillator (S-ICD) is established as an alternative to transvenous implantable defibrillators. However, extended follow-up data is rare. The present analysis presents real-world data from patients with S-ICD and a follow-up duration of 10 years or more from a large prospective single center cohort.
Methods and Results: Between July 2010 and November 2013 76 S-ICD systems were implanted at our institution. 40 patients (52.6%) were implanted for primary prevention of sudden cardiac death. After a follow-up duration of 10 years data from 67 patients (88.1%) was available. Mean follow-up duration was 10.7±1.3 years.
44 patients (65.7%) were still alive with active S-ICD therapy. 8 patients (11.9%) died during follow-up. Three of these were patients with a severe state of cyanotic congenital heart disease while 2 died after a longer period of support by a left ventricular assist device (LVAD). One further patient died from a sepsis under immunosuppression while in two individuals the cause of death remains unknown. In 8 patients (11.9%), conversion to a transvenous ICD system was necessary. This was either due to heart failure with indication for biventricular pacing (n=2), significant episodes of bradycardia (n=3), oversensing that could not be solved (n=2), or a pocket infection (n=1). In four patients (6%), the S-ICD system was explanted without replacement for different individual reasons.
16 patients already underwent two generator replacements while one generator replacement was performed in the rest of the cohort. Generator longevity therefore was documented to be within the predicted values of the 1st and 2nd generation S-ICDs. In 10 patients (14.9%), appropriate therapy delivery for ventricular arrhythmias was delivered. In 12 patients (17.9%), inappropriate shock delivery due to oversensing occurred. Of note, this could be resolved in all but two patients. Furthermore, the majority of these episodes occurred in the early years before implementation of the SMART Pass algorithm.
Conclusion: The S-ICD has demonstrated to be a reliable defibrillator system over a period of more than ten years. S-ICD therapy can be successfully maintained over a long time. Incidence of oversensing significantly decreased with implementation of novel algorithms and the new S-ICD generation. However, the present data clearly indicates that in selected individuals conversion to transvenous systems must be considered.