Mechanisms of Slow Ventricular Tachycardias in Acute Myocardial Infarction

Unifocal ventricular rhythms with rates between 60 and 100 per minute were classified as slow ventricular tachycardias when occurring in patients with acute myocardial infarction. Analysis of selected electrocardiograms showed that the paroxysms were usually automatic, nonparasystolic and intermittent However, in one case, the arrhythmia resulted from the exit block of a faster, parasystolic, ventricular tachycardia. The first ectopic beat in each series appeared either as an escape or as a late extrasystole. Variations in rate attributed to a disturbance of automaticity and/or conductivity were frequently observed. The erratic and unpredictable behavior of this arrhythmia probably reflected the unstable condition of the injured cells during the early stages of myocardial infarction.