Long-Term Follow-Up of Primary and Secondary Prevention Implantable Cardioverter Defibrillator Patients

Aims The beneficial effects of implantable cardioverter defibrillators (ICDs) in primary and secondary prevention patients are well established. However, data on potential differences between both groups in mortality and ICD therapy rates during long-term follow-up are scarce. The aim of the study was to assess differences in mortality and ICD therapy between secondary and primary prevention ICD recipients.Methods and results With the exception of patients with congenital monogenetic cardiac disease, all patients treated with an ICD, regardless of the underlying cardiac pathology, from 1996 to 2008 at the Leiden University Medical Center were included in the current analysis. The study population was grouped by the type of prevention (secondary or primary) for sudden cardiac death. The primary endpoint was all-cause mortality. The secondary endpoint was the occurrence of device therapy (appropriate or inappropriate). A total of 2134 (80% men, mean age 63 +/- 12 years) ICD recipients were included. Of these, 1302 (61%) patients received an ICD for primary prevention of sudden cardiac death and 832 (39%) patients for secondary prevention. During a mean follow-up of 3.4 +/- 2.8 years, 423 (20%) patients died. The 5-year cumulative incidence of mortality was 25% [95% confidence intervals (CI): 21-29%] for primary prevention patients and 23% (95% CI: 20-26%) for secondary prevention patients. Secondary prevention patients exhibited a 74% increased risk for appropriate therapy when compared with primary prevention patients [hazard ratios (HR): 1.7; P < 0.001]. A comparable risk for inappropriate shocks was observed (HR: 1.0; P = 0.9).Conclusion During long-term follow-up, primary prevention patients exhibited a lower risk of appropriate therapy, but comparable mortality rates were observed between both groups. Both groups showed similar occurrence of inappropriate shocks.