LATE POTENTIALS, QTC PROLONGATION, AND PREDICTION OF ARRHYTHMIC EVENTS AFTER MYOCARDIAL-INFARCTION

In a series of 171 consecutive survivors of acute myocardial infarctio n, the predictive value of late potentials and QTc prolongation was pr ospectively assessed. QT intervals were measured in lead V-2, correcte d QT (QTc) was calculated using Bazett's equation (cut-off value 440 m s). Late potentials were considered to be present when all of the thre e signal-averaged electrocardiographic variables were abnormal (i.e. Q RS > 114 ms, D-40 > 38 ms, and V-40 < 20 mu V). Complete follow-up was obtained (mean 13 +/- 6 months, range 6-24 months). Six percent of th e patients had an arrhythmic event (i.e. sustained ventricular tachyca rdia or sudden death). The relative risk of late potentials for arrhyt hmic events was 7.7 (P < 0.02). The relative risk of QTc > 440 ms was 1.1 (NS). In a multivariate analysis, the addition of QTc prolongation did not significantly improve the prognostic value of late potentials alone. It is concluded that late potentials are predictive of arrhyth mic events after myocardial infarction, but the presence of concomitan t QTc prolongation does not worsen the prognosis.