The implantable automatic defibrillator

The stringent criteria required for a clinically applicable automatic ventricular defibrillator have now been satisfied. The hermetically sealed unit is encased in titanium, weighs 250 g, and occupies a volume of 145 cc. Continously monitoring cardiac electrical activity, the device detects ventricular fibrillation when isoelectric potential segments disappear and restore normal rhythm with a truncated exponential pulse of 30 joules delivered 15 seconds after onset of the dysrhythmia. The operational status of the defibrillator can be tested noninvasively in vivo with an external analyzer. Functional performance of the device has been evaluated in nonanesthetized, active animals by inducing ventricular fibrillation with a specially designed implanted fibrillator. The resulting syncope mimics the clinical entity of sudden death, but in contrast to stricken patients, the animals are automatically defibrillated and resuscitated with the implanted defibrillator. Pilot clinical studies of this approach to prevention of sudden death from ventricular fibrillation are scheduled to begin in the near future.