Ventricular parasystole in acute myocardial infarction.

The clinical and electrocardiographic features of 11 patients with ventricular parasystole in acute myocardial infarction are described. This arrhythmia always appeared within the first 24 hours after the beginning of the pain, and lasted usually a few hours. Only one patient received digitalis before the appearance of the arrhythmia; the others did not receive any drug of known arrhythmic potential. The treatment was mainly with lignocaine intravenously, the response to which was usually very good. There was no relation between this arrhythmia and the plasma potassium levels. The electrocardiographic finding of fusion beats, coupling, retrograde conduction, interectopic interval, ectopic cycle length, and exit block were analysed. Two of the cases were examples of intermittent parasystole. The relation between this arrhythmia and the slow idioventricular rhythm was discussed. It appears that this is a benign arrhythmia, easily controlled by treatment, produced perhaps by the same mechanisms as ventricular tachycardia, but with the existence of exit block.