Long-Term Follow-Up of the S-ICD: A 10-Years Follow-Up Study of a Large Single Center Cohort

The subcutaneous implantable defibrillator (S-ICD) is an alternative to transvenous implantable defibrillators. The present analysis presents real-world data from patients with S-ICD and a follow-up duration of 10 years or more.

Between July 2010 and November 2013 76 S-ICD systems were implanted. 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. Forty-seven patients (70.2%) were still alive with active S-ICD therapy. Eight patients (11.9%) died during follow-up. In eight 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), bradycardia (n = 3), oversensing that could not be solved (n = 2), or pocket infection (n = 1). In four patients (6%), the S-ICD system was explanted without replacement for individual reasons. Sixteen patients already underwent two generator replacements, while one generator replacement was performed in the rest of the cohort. Therefore, generator longevity was documented to be within the predicted values. 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 the implementation of the Smart Pass algorithm.

S-ICD therapy can be successfully maintained over a long time. Incidence of oversensing significantly decreased with the implementation of novel algorithms and the new S-ICD generation. However, the present data also points out that in selected individuals conversion to transvenous systems is required.