Prognostic significance of late ventricular potentials after acute myocardial infarction

The prognostic significance of late ventricular potentials recordedfrom the body surface using high-gain amplification and signalaveraging was assessed prospectively in 160 patients (mean age56±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 presentin 48 patients (30%). The mean duration of late potentials was27 ± 16.5 ms. There was no significant correlation withthe frequency and type of spontaneous ventricular arrhythmiasduring 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 afterdischarge was uneventful. Sudden cardiac death occurred in sevenpatients (4.4%) after 3.7± 3.4 months (range 0.7–8.3months). Sustained ventricular tachycardia was documented infour cases 2.9± 1.3 months after myocardial infarction,all having late potentials. The overall incidence of ventriculartachycardia in patients with late potentials of 20 ms durationand more was four out of 48 patients (8.3%) increasing to 16.6%(three out of 18 patients) if only patients with late potentialsgreater than 40 ms were considered. Sudden cardiac death occurredin three of 79 patients (3.8%) without late potentials. In patientswith late potentials less than 40 ms duration, the incidenceof sudden death was 3.2% (two out of 63 patients), but it increasedto 11.1% (two out of 18 patients) with late potentials of 40ms duration or more. Ventricular tachycardia or sudden deathoccurred in 21.7% of patients with late potentials and anteriorwall infarction compared to 5.4% in patients with late potentialsand inferior wall infarction (P<0.05). Only one of 79 patients(1.3%) without late potentials died non-suddenly from a cardiaccause (reinfarction) compared to three of 81 patients (3.7%)with late potentials irrespective of duration. Thus, this prospective multicentre pilot study suggests thataveraging might be a promising non- invasive technique for theidentification of patients prone to ventricular tachycardiaor possibly even sudden death after recent acute myocardialinfarction.