Incidence and Pattern of Ventricular Late Potentials in the First Ten Days Following Acute Myocardial Infarction

In contrast to studies of late potentials (LP) during the chronic stage of myocardial infarction (MI), little has been published about signal averaged LP during the acute phase of MI. We therefore investigated the occurrence of LP during the first 10 days following acute MI in daily measurements of the signal averaged ECG. Thirty‐three patients with acute MI defined by clinical, history, diagnostic electrocardiographic changes, and enzymatic evaluation were prospectively included in the study. Thirty‐three percent suffered from anterior MI, 43% from inferior MI, and 24% had MI in both regions. Using the method of Simson, an LP was defined as a mean voltage of < 25 ±V in the last 40 msec of the filtered QRS complex. The incidence of LP ranged between 24% on the first day and 39% on day 6. There was no significant difference comparing the incidence of LP between consecutive days. Looking at the individual patient, only 3 patients exhibited a constant LP, 15 patients remained without LP, and 15 patients showed a variable incidence over the course of 10 days. There was no correlation between the incidence of LP and the localization of MI or the maximum level of the CK‐MB isoenzyme.