Of the 733 patients with implantable cardioverter-defibrillators (ICDs) from 1982 to 1995 in our center, 20 died suddenly while the ICD was activated. This number included 16 men and four women with a mean age of 60 +/- 8 years and ejection fractions of 24.2% +/- 8.6%. ICDs were implanted for drug refractory ventricular tachycardia (VT) in 13 patients and for resucitated cardiac arrest in seven patients. The clinical VT was associated with syncope in 7 of 13 patients. VT was induced in 18 patients and was hemodynamically unstable in 12 patients. Shock therapies associated with syncope were delivered in 7 of 15 patients during the follow-up. This subgroup of patients survived a median of only 18 months after ICD implant. Ventricular fibrillation-defibrillation was found to surround death in nine patients.
Conclusions: (1) Sudden death victims of the ICD population are characterized by poor left ventricular function and hemodynamically unstable ventricular tachyarrhythmias. (2) Ventricular tachyarrhythmias are the major cause of sudden death in ICD patients.