LATE POTENTIALS AND VENTRICULAR ENLARGEMENT AFTER MYOCARDIAL-INFARCTION - A NEW ROLE FOR HIGH-RESOLUTION ELECTROCARDIOGRAPHY

Background. Arrhythmias are common in patients who have developed ventricular enlargement after myocardial infarction. Methods and Results. A prospective study was undertaken to assess the relation between ventricular dilatation and the development of late potentials after myocardial infarction. Echocardiograms and signal-averaged ECGs were recorded on days 1, 3, 7, and 42 in 52 patients with a first anterior myocardial infarction. Twenty-nine percent of patients were late potential-positive on their initial signal-averaged ECG recorded on the day of admission. The incidence of late potentials rose during the next week to a peak of 42% at day 7, declining to 13% by day 42. The presence of late potentials on the day of admission was associated with an increase in end-diastolic volume index of 16.1+/-6.0 mL/m2 (mean+/-SEM), compared with a decrease of 4.7+/-2.7 mL/m2 among late potential-negative patients (P<.006). Qualitatively similar results were evident for late potentials on day 3 and day 7. By contrast, there was no association between late potentials on day 42 and ventricular dilatation. Marked dynamic changes in late potentials were evident during the first week. Patients with persistent late potentials (n=9) on all three recordings in the first week showed a marked increase in end-diastolic volume index of 21.3+/-8.1 mL/m2 (P<.005 in comparison with patients who were persistently negative [n=20]). Patients demonstrating dynamic positivity (n=15) not present on all three recordings in the first week showed no significant increase in end-diastolic volume index. Conclusions. It is concluded that late potentials during the first week after infarction are associated with subsequent ventricular dilatation. These early-phase late potentials may be a manifestation of cell slippage. They arise before gross topographical enlargement and may serve as a predictor of ventricular dilatation.