Delayed ventricular depolarization--correlation with ventricular activation and relevance to ventricular fibrillation in acute myocardial infarction.

Signal averaging to detect abnormalities in the terminal phase of ventricular depolarization has been performed in several groups of patients with various manifestations of ischaemic heart disease. Late potentials were common in patients with VT and in a group of patients having cardiac surgery. Findings in the surgical group highlighted the close correlation of late potentials with delayed, fragmented epicardial activation supporting the hypothesis that late potentials reflect a myocardial substrate which would support re-entrant VT. The findings in the surgical group allowed a definition of late potentials which could be applied to other patients in the study, and also demonstrated a spectrum of late depolarization abnormalities. Signal averaging is technically feasible in the noisy CCU environment but late potentials were detected in few patients early in AMI. Late potentials were also rarely seen in patients with VF and therefore cannot be construed as a predictive index of this arrhythmia.