Clinical Outcomes of Single- versus Dual-Chamber Implantable Cardioverter Defibrillators: Lessons from the Israeli ICD Registry.

Objective: To compare the clinical outcomes of a single- versus dual-chamber ICD for primary prevention of sudden cardiac death in a large, national ICD registry.

Methods: Data were collected from the prospective Israeli ICD Registry. Baseline characteristics and clinical outcomes including mortality, admissions for heart failure (HF), and ICD therapy were compared between the two groups.

Results: A total of 1,125 subjects, 37% with a single-chamber and 63% with a dual-chamber ICD, constructed the baseline cohort. Approximately 80% had ischemic heart disease (IHD). Mean follow-up was 22 months, mean ejection fraction was 30%, and mean QRS width was 103 milliseconds in both groups. During follow-up, there were no significant differences in the rate of mortality, admissions for HF, appropriate or inappropriate therapy, or in time to any of the clinical outcomes. Using multivariate analysis, single-chamber ICD was not associated with increased risk of death or admission for HF. In a subgroup of patients with IHD, single-chamber ICD was associated with a higher rate of inappropriate therapy.

Conclusions: In this large retrospective population-based cohort, dual-chamber ICD showed no benefit in reducing the incidence of death or HF admissions, whereas in a subgroup of patients with IHD, single-chamber ICD was associated with increased inappropriate therapy. Further prospective studies are necessary to assess the benefit of dual-chamber ICD in reducing the rate of inappropriate therapy.