Single-chamber ICD, single-zone therapy in primary and secondary prevention patients: the simpler the better?

It is now well established that implantable cardioverter defibrillator (ICD) implantation reduces mortality in patients at increased risk of sudden cardiac death. However, the best programming parameters remain controversial. Our traditional policy has followed a simple approach in the vast majority of patients. In accordance with ICD programming in the major randomized clinical trials, we programmed a single high-rate, shock-only therapy zone. We aimed to demonstrate in this observational study that simple programming is not associated with higher shock rates or mortality when compared to other published studies.

Consecutive patients who underwent single-chamber ICD implantation with single-zone, high-rate programming at our institution between 1993 and 2008 were retrospectively studied. Data were collected prospectively in a database regarding details of ICD implantation, demographic data, and indication.

Three hundred thirty-two patients were included in our study, 31 % primary prevention and 68 % secondary prevention. Mean ejection fraction (EF) is 33.7 ± 15.3. Over a mean follow-up period of 62.5 ± 38.1 months, 135 patients experienced ICD shock (annualized event rate 7.7 %); 89 patients (26.8 %) appropriate shock in VT-ventricular fibrillation (VF), 68 patients (20.5 %) inappropriate shocks, and 22 patients (6.6 %) both. Twenty-nine patients (8.7 %) were reprogrammed to additional VT-ATP zones. Twenty-two (6.6 %) patients underwent heart transplantation. Sixty-two patients (18.6 %) died during follow-up, 43.6 % out of them due to cardiac cause, mainly progressive heart failure.

Our results show that simpler settings with single-zone, high-rate programming is associated with ICD shock rates and long-term mortality that does not appear to be worse when compared with contemporary studies which include multizone ICD programming with antitachycardia pacing activated.