Incidence of ventricular arrhythmias in first year after myocardial infarction.

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Abstract
The incidence of ventricular arrhythmias in the 1st yr after acute myocardial infarction was studied prospectively using 24 h Holter ECG tape monitoring. Of 108 patients beginning the trial, 74 completed the 12 mo. of study. Patients were initially studied at 2 wk after infarction then at 3 mo. intervals. Ventricular premature beats were observed in 80% of studies, with these arrhythmias occurring in 57% of the total hours studied. Significant ventricular arrhythmias defined as ventricular premature beats greater than 1 in 10 beats, multifocal ventricular premature beats, bigeminy or trigeminy, salvos (2 or 3 consecutive ventricular premature beats), R on T or ventricular tachycardia (4 or more ventricular premature beats), occurred in 54% of studies, with these arrhythmias occurring in 40% of the total hours studied. The incidence of ventricular arrhythmias remained fairly constant for each 3 mo. period. The percentage of total studied hours for which ventricular arrhythmias occurred was significantly higher after the entry study at 2 wk. The incidence of ventricular arrhythmias was significantly higher in patients with inferior or posterior infarction after the entry study compared with those with anterior infarction (P < 0.005). Patients who had cardiac failure in the coronary care unit or a peak serum aspartate aminotransferase > 200 IU/1 had a higher long-term incidence of ventricular arrhythmias (P < 0.01). Four deaths occurred during the study. In all cases ventricular premature beats were observed on at least 1 study period with significant ventricular premature beats in 2 of the 3 patients who died suddenly. A control group of 21 normal subjects had a random 24 h Holter study and had a significantly lower incidence of ventricular arrhythmias when compared with the post-infarction group. Ventricular premature beats were observed in 48% of cases (P < 0.005) for 28% of the total hours studied (P < 0.025) and significant ventricular arrhythmias in 19% of cases (P < 0.005) for 35% of the total hours studied. The standard ECG was a poor indicator of the true incidence of ventricular premature beats found on 24 h Holter monitoring, with 75% of patients having ventricular arrhythmias and 43% showing significant ventricular arrhythmias when all standard ECG showed no ventricular premature beats.