Automatic implantable cardioverter-defibrillator: Patient survival, battery longevity and shock delivery analysis

The automatic implantable cardioverter-defibrillator (AICD) has been shown to reduce the mortality rate of patients with malignant ventricular tachyarrhythmias. This report describes experience with implantation of 36 automatic implantable cardioverter-defibrillators (AId-B and AID-BR models) in 22 persons over a 44 month patient follow-up period (mean 19.6 months). There were five deaths: two patients died suddenly 22 and 29 months, respectively, after their second implant, one died of congestive heart failure, one died of respiratory failure and one died of catheter sepsis. Although 11 (50%) of the 22 patients never received a countershock for a ventricular tachyarrhythmia and are still alive, the other 11 received one or more spontaneous countershocks. Nine patients (41%) experienced spurious shocks during the follow-up period. Assuming that the first shock for presumed ventricular tachyarrhythmia prevented death, the hypothetical cumulative survival of patients at 42 months would have been 34 ± 14.1% in the absence of an automatic implantable cardioverter defibrillator rather than the actual survival rate of 59 ± 16.8%. The cumulative device survival of the 36 AID-B units was 92 ± 5.62% at 15 months but diminished to 37 ± 14.4% by 20 months. No unit lasted longer than 22 months. There were 12 battery depletions. The number of shocks emitted did not influence unit longevity. The manufacturer's elective replacement indicator is of uncertain validity. Six units remained active 7 to 17 months after surpassing their replacement indicator. The automatic implantable cardioverter-defibrillator prolongs the life of many patients with otherwise intractable arrhythmias. Problems remain with this early generation device including the imprecision of its arrhythmia detection system resulting in false-positive discharges, the limited longevity of its battery, lack of programmability and an inadequate device follow-up system.