[Late potentials in patients during the hospitalization period following acute myocardial infarction]

Serial signal-averaged electrocardiograms were recorded every 72 hours in 60 patients admitted to the coronary care unit with acute myocardial infarction. The prevalence of late potentials was 61.6% (37 patients) during hospitalization. Of these 37 patients, late potentials appeared transiently in 20 (54%), while in 9 patients (24%), once late potentials had appeared, they tended to persist. No specific clinical characteristics were related to the development of late potentials (site of infarction, peak creatine kinasa activity, Killip class, thrombolytic therapy). The presence of late potentials did not identify patients who developed clinically significant ventricular tachyarrhythmias (primary ventricular fibrillation, ventricular tachycardia). The abnormal late potentials were modified by the administration of lidocaine. This lack of correlations suggests that the abnormal signal averaged electrocardiogram and complex ventricular arrhythmias during acute myocardial infarction have different electrophysiological bases. Late potentials could be only a bystander electrophysiological phenomenon without clinical correlation in this clinical phase.