Efficacy of the automatic implantable cardioverter-defibrillator in prolonging survival in patients with severe underlying cardiac disease.

The ability of the automatic implantable cardioverter-defibrillator to prolong overall survival, particularly in patients with significantly depressed cardiac function, has not been well documented. Of 119 patients who received the implantable defibrillator in this institution, 40 had a left ventricular ejection fraction less than 30% (Group A) and 79 had an ejection fraction greater than or equal to 30% (Group B). For each group, cumulative survival was compared with the projected survival if the implantable defibrillator had not been used. Projected survival was based on the assumption that the first appropriate shock would have resulted in death without the defibrillator. For Group A, the 3 year cumulative survival rate was 67 +/- 12% versus a projected survival rate of 6 +/- 15% (p less than 0.001). For Group B, the 3 year cumulative survival rate was 96 +/- 3% versus a projected survival rate of 46 +/- 8% (p less than 0.001). Both the cumulative and projected survival rates for patients in Group A were significantly worse than for patients in Group B (p less than 0.01). The projected survival rates for both Groups A and B were comparable with the observed survival rate in similar patients treated without the implantable defibrillator. In summary, the implantable cardioverter-defibrillator significantly prolonged overall survival, even in patients with poor cardiac function. The technique of estimating projected survival appears to allow a realistic estimate of the reduction in mortality achieved by the defibrillator.