[Clinical and electrophysiologic findings in patients with syncope following myocardial infarct].

34 patients with syncope (median number of episodes 2) which remained unexplained after thorough medical and neurological evaluation underwent an intracardiac electrophysiological study with atrial and ventricular programmed stimulation. All patients had a history of well-documented myocardial infarction 24 months (median, 3-120) prior to the electrophysiological study. During programmed ventricular stimulation 6 patients had inducible ventricular fibrillation or flutter, and 10 patients had sustained ventricular tachycardia. In 14 patients non-sustained ventricular tachycardia was induced, whereas in only 4 patients 1 to 3 repetitive ventricular responses were induced. Therapy was instituted on the basis of electrophysiologic testing. During the follow-up of 8 months (median, 1-37) 27 patients had no recurrence of syncope. Syncope persisted and remained unexplained by the electrophysiological study in 3 patients. One patient had ventricular fibrillation and two died suddenly, two of these patients after having discontinued antiarrhythmic medication 2 weeks before. Another patient died of non-cardiac cause. It is concluded that 1) the results indicate a high ventricular vulnerability (88%) in patients with unexplained syncope after myocardial infarction, 2) the evaluation by electrophysiological studies may identify the potential mechanism for syncopes, 3) electrophysiological testing offers a rationale for specific prophylactic therapy.