Gender-specific differences in S-ICD therapy: long-term follow-up of a large single-center cohort

Background: The totally subcutaneous implantable defibrillator (S-ICD) is established as an alternative to transvenous implantable defibrillators. However, long-term follow-up data is rare. The present analysis presents real-world data from patients with S-ICD and aims at characterizing gender-specific differences in a large prospective single center cohort.

Methods and Results: The present study included 241 patients with a minimal follow-up duration of 5 years. 166 patients (68.9%) were male and mean follow-up duration was 7.4±2.3 years. Of note, male patients were significantly older than female patients (44.9±16.7 vs. 38.0±12.8 years, p=0.0017).

Regarding baseline characteristics, ischemic cardiomyopathy was more prevalent in male patients (22.9% vs. 4.0%, p<0.001) while electrical heart disease was a more frequent finding in women (25.3% vs. 12.0%, p<0.001). No significant differences were found for dilated cardiomyopathy, hypertrophic cardiomyopathy and idiopathic ventricular fibrillation. In male patients, a higher proportion of primary prevention was observed (53.3% vs. 46.7% in female patients, p>0.01). Left ventricular ejection fraction did not significantly differ between male (49.4%±15.1) and female (51.8±13.3%, p=0.21) patients.

During follow-up, mortality did not significantly differ between both groups while a trend towards an increased rate of deaths in male patients (9.0% vs. 6.7%, p=ns) was observed. The rate of system change to transvenous systems was 8% in both groups. Likewise, the rate of system explantation did also not differ between both groups. No significant differences were observed for appropriate or inappropriate shock deliveries in both groups.

Conclusion: The S-ICD has demonstrated to be a reliable defibrillator system over a period of more than ten years. In the present cohort, male patients were significantly older and the prevalence of ischemic cardiomyopathy was higher. No significant differences were observed for appropriate or inappropriate shock deliveries in both groups. These results are similar to those of large studies in transvenous ICD systems and can most likely be explained by the differences in baseline characteristics.