Abstract

Objectives: To assess the incidence and electrophysiological characteristics of spontaneous ventricular tachyarrhythmias after implantable cardioverter-defibrillator (ICD) implantation for primary prevention.

Design: Prospective observational study.

Patients: 41 consecutive patients, who fulfilled MADIT (multicenter automatic defibrillator implantation trial) I criteria, except for suppressibility by procainamide, and who received a prophylactic ICD.

Interventions: Subpectoral implantation of an ICD.

Main outcome measures: Incidence of ventricular tachyarrhythmias and their electrophysiological characteristics with respect to timing of the arrhythmia, tachyarrhythmia cycle length, mode of termination, and clinical relevance.

Results: During a mean (SD) follow up of 30 (21) months 18 of 41 (43.9%) patients experienced 142 appropriate ICD treatments. The mean (SD) time to first event was 9.6 (15.1) months. One patient had ventricular fibrillation (VF), 12 patients ventricular tachycardia (VT), and five both VT and VF. The mean (SD) cycle length of monomorphic VT was 306 (42) ms. Of 142 episodes, 117 (82.3%) were terminated by antitachycardia pacing and another 25 (17.6%) by ICD discharges. Cumulative survival of hypothetical death, defined as treated VT with a cycle length < 260 ms or VF, was 83.2% after one year and 78.4% after two years.

Conclusions: Patients with a left ventricular ejection fraction < 35%, a history of myocardial infarction, non-sustained VT, and inducible VT/VF are at high risk of VT/VF early after implantation. Therefore, implantation of a tiered treatment defibrillator seems to be justified.