Survival and Appropriate Device Interventions in Recipients of Cardioverter Defibrillators Implanted for the Primary Versus Secondary Prevention of Sudden Cardiac Death

Background: Implantable cardioverter-defibrillators (ICD) implanted after an episode of ventricular tachyarrhythmia (VTA) or in patients at high risk of VTA lower the long-term mortality. Comparisons of the clinical outcomes of the two indications are scarce. Methods: The study enrolled 360 consecutive ICD recipients. The device was implanted for secondary prevention in 150 patients, whose mean age was 60 ± 14 years, and mean left ventricular ejection fraction (LVEF) was 40 ± 16%, and for primary prevention in 210 patients, whose mean age was 61 ± 11 years, and mean LVEF was 31 ± 13%. All-cause mortality and time to first appropriate ICD therapy were measured. Results: The two study groups were similar with respect to age and prevalence of coronary artery disease. Mean LVEF was higher in the secondary prevention group (P = 0.001). Cox regression analysis revealed a significantly shorter time to first appropriate ICD therapy in the secondary prevention group (HR = 0.51, 95% CI = 0.30 – 0.87, P = 0.01). Over a mean follow-up of 37 ± 19 months, the all-cause mortality in the overall population was 12.7%, and was similar in both subgroups (HR = 0.99, 95% CI = 0.55–1.77, P = 0.97). Conclusions: The long-term mortality in this unselected population of ICD recipients was low. Patients treated for secondary prevention received earlier appropriate ICD therapy than patients treated for primary prevention. Long-term mortality was similar in both groups. The higher VT incidence of VTA was effectively treated by the ICD and was not associated with a higher mortality.