An automatic implantable cardioverter-defibrillator with pacemaker was implanted in Cuba, in ten patients with malignant ventricular arrhythmias, sudden cardiac collapse, and ventricular tachycardia with syncope, after a previous electrophysiological study for analysis of the arrhythmia and pharmacological evaluation. The patients were 9 males, ranging in age from 23 a 70 years, with a mean of 48 years, and an ejection fraction of 32% (18-62%). The etiologies were: an old myocardial infarction (7 cases) and dilated cardiomyopathy (3 cases). During the follow-up, mean from 2 to 25 months, four patients received effective shocks for rapid palpitations and presyncope. Two patients died, one due to incessant ventricular tachycardia and one of a cause unrelated to device. We concluded that the GUARDIAN 4201 and 4202 device are useful to prevent sudden cardiac death in high risk patients who experienced a life threatening arrhythmia.