Determinants of late potentials in myocardial infarction.

To clarify factors which have an influence on late potentials (LPs), signal averaged electrocardiogram, echocardiogram, cardiac catheterization and Holter monitoring were studied in 86 patients with previous myocardial infarction (MI). Group 1 consisted of 27 patients with LPs (LP duration greater than or equal to 20 msec) and Group 2 consisted of 59 patients without them. Twelve percent of anterior MI and 35% of inferior MI had LPs. Left ventricular (LV) diastolic dimension was larger and % fractional shortening was lower in group 1 than those in group 2. LV end-diastolic volume index and LV end-systolic volume index were larger and LV ejection fraction was lower in group 1 than those in group 2. Aneurysm was noted in 37% in group 1 and 17% in group 2 (p less than 0.05), and mean number of involved coronary vessels was 2.3 +/- 0.8 in group 1 and 1.7 +/- 0.8 in group 2 (p less than 0.05). No significant difference was found in other clinical and hemodynamic parameters. The incidence of patients with 100 or more ventricular premature contractions per hours and that with ventricular tachycardia (VT) were significantly higher in group 1 than in group 2 (26% vs 7%, p less than 0.05, 33% vs 7%, p less than 0.01, respectively). Multiple regression analysis and the method of quantification demonstrated that ventricular arrhythmia was most strongly associated with LP duration.