Occurrence of ICD shocks and patient survival.

Fifty-six consecutive patients who underwent initial implantation of an implantable cardioverter defibrillator (AICD) between May 1982 and January 1990 were analyzed. During a mean follow-up of 31.5 +/- 25 months, 32 (60%) patients experienced a spontaneous shock from their device. Their clinical characteristics and survival were compared to those of 21 patients without shocks. No statistically significant difference was found in the distribution between the two groups in age, sex, cardiac diagnosis, New York Heart Association Class, presenting arrhythmia, or mean follow-up (F/U). The group with shocks had a higher incidence of previous MI (P = 0.021) a lower mean ejection fraction (P = 0.023) and had been tried on a greater number of medical regimens (P = 0.003). The 1-, 3-, and 5-year cumulative survivals were 84%, 69%, and 37% in the group with shocks and 93%, 93%, and 93% for the group without shocks. Our data suggests that the occurrence of a shock is a negative prognostic indicator and that the excellent prognosis of patients without shocks contributes in large part to the favorable outcome of AICD patients.