Automatic implantable cardioverter defibrillators delivered appropriate shocks to 64% of patients by 4 years, while the cumulative incidence of spurious shocks plateaued at about 12 months.
Cohort (n=65)
What is the incidence and pattern of shocks in patients following implantation of an automatic implantable cardioverter defibrillator?
The majority of patients with an implantable defibrillator receive appropriate shocks during long-term follow-up, with the cumulative incidence of appropriate shocks increasing steadily for at least 4 years.
The actuarial incidence and pattern of occurrence of shocks were analyzed in 65 patients after implantation of the automatic implantable cardioverter defibrillator. During a mean follow-up of 25 +/- 21 months only one patient died suddenly, and this patient had a nonfunctioning device at the time of death. The long-term actuarial risk of death from any cause in the patients who received appropriate shocks was not significantly different than for the entire group. The 1- and 4-year cumulative risk of receiving any shock was 51 +/- 7% and 81 +/- 11%; of receiving an appropriate shock was 33 +/- 7% and 64 +/- 10%; of receiving a spurious shock was 17 +/- 5% and 21 +/- 6%; and of receiving an "indeterminate" shock was 19 +/- 6% and 52 +/- 10%. In 14 patients who were followed for 24 months without receiving an appropriate shock, the actuarial risk of receiving an appropriate shock was 29 +/- 14% during the next 24 months. The mean number of shocks delivered during appropriate episodes was 1.6 +/- 0.9, which was significantly lower than the mean of 4.0 +/- 2.0 shocks during spurious episodes (P less than 0.02). The mean number of shocks during indeterminate episodes was 1.7 +/- 1.5. Our data confirms the efficacy of the implantable defibrillator in preventing sudden death. The majority of patients with this device receive appropriate shocks during long-term follow-up, and the cumulative incidence of appropriate shocks increases steadily for at least 4 years. In contrast, the cumulative incidence of spurious shocks plateaus at about 12 months. Our data suggests that many "indeterminate" shocks actually appear to be appropriate.
Fogoros et al. (1989) conducted a cohort in Patients after implantation of the automatic implantable cardioverter defibrillator (n=65). Automatic implantable cardioverter defibrillator was evaluated on Actuarial incidence and pattern of occurrence of shocks. Automatic implantable cardioverter defibrillators delivered appropriate shocks to 64% of patients by 4 years, while the cumulative incidence of spurious shocks plateaued at about 12 months.