Six-year follow-up of the initial Dutch subcutaneous implantable cardioverter-defibrillator cohort: Long-term complications, replacements, and battery longevity.

INTRODUCTION: Experience with the subcutaneous implantable cardioverter-defibrillator (S-ICD) is expanding rapidly. However, data on long-term performance or complications related to elective generator replacement are lacking.

METHODS: Follow-up (FU) data of all patients implanted between December 2008 and April 2011 were collected. Complications were defined as those requiring surgical intervention. Kaplan-Meier estimates for complication and shock rates, with corresponding 95% confidence intervals (CI), were calculated.

RESULTS: One hundred and eighteen patients were included. Median FU was 6.1 years (IQR 5.6-6.5 years). Short-term complication rate (0-30 days) was 3% (CI 0-6%). Long-term complication rate at 6 years was 19% (CI 12-26%), corresponding with an annual complication rate of 3%. One patient in this cohort developed a need for a transvenous ICD (TV-ICD) in order to provide pacing for bradycardia (1%). Six patients were implanted with a TV-ICD after experiencing an S-ICD complication for which extraction was necessary. In total, 10 S-ICDs were extracted; none resulted in a complication. Eight patients had a nonsystemic ICD-related infection and no lead failures were observed. The majority, 68 (58%) patients, received an elective generator replacement. Two patients had a complication related to generator replacement (3%). Battery longevity was 5.6 years (IQR 5.2-6.1). Appropriate and inappropriate shock rates of 6-year estimates were 17% (CI 9-25%) and 21% (CI 15-27%), respectively.

CONCLUSIONS: This cohort represents the longest follow-up to date and shows a low annual complication rate without lead failures or systemic infections. Battery longevity of the first S-ICD generation results in relative early generator replacement procedures.