Prognostic significance of late ventricular potentials after acute myocardial infarction.

Abstract

The prognostic significance of late ventricular potentials recorded from the body surface using high-gain amplification and signal averaging was assessed prospectively in 160 patients (mean age 56±8.3 years) after recent acute myocardial infarction (median day of study 25.5). Late potentials were recorded in 81 out of 160 patients (50.6%); a duration of less than 20 ms was observed in 33 patients (20.6%), whereas late potentials of 20 ms duration or more were present in 48 patients (30%). The mean duration of late potentials was 27 ± 16.5 ms. There was no significant correlation with the frequency and type of spontaneous ventricular arrhythmias during 10–24 h Holter monitoring. The follow-up period was 7.5±3.2 months (mean ±s.D.; maximum 15.8 months). In 136 patients (85%) the course after discharge was uneventful. Sudden cardiac death occurred in seven patients (4.4%) after 3.7± 3.4 months (range 0.7–8.3 months). Sustained ventricular tachycardia was documented in four cases 2.9± 1.3 months after myocardial infarction, all having late potentials. The overall incidence of ventricular tachycardia in patients with late potentials of 20 ms duration and more was four out of 48 patients (8.3%) increasing to 16.6% (three out of 18 patients) if only patients with late potentials greater than 40 ms were considered. Sudden cardiac death occurred in three of 79 patients (3.8%) without late potentials. In patients with late potentials less than 40 ms duration, the incidence of sudden death was 3.2% (two out of 63 patients), but it increased to 11.1% (two out of 18 patients) with late potentials of 40 ms duration or more. Ventricular tachycardia or sudden death occurred in 21.7% of patients with late potentials and anterior wall infarction compared to 5.4% in patients with late potentials and inferior wall infarction (P<0.05). Only one of 79 patients (1.3%) without late potentials died non-suddenly from a cardiac cause (reinfarction) compared to three of 81 patients (3.7%) with late potentials irrespective of duration. Thus, this prospective multicentre pilot study suggests that averaging might be a promising non- invasive technique for the identification of patients prone to ventricular tachycardia or possibly even sudden death after recent acute myocardial infarction.