Further Observations on Ventricular Tachycardia As Studied by Electrical Stimulation of the Heart

Initiation and termination of tachycardia was studied by electrical stimulation of the heart in 14 patients with ventricular tachycardia (VT) not related to acute myocardial infarction (group A) and in six patients in whom the tachycardia occurred within 24 hours after the onset of acute myocardial infarction (group B). Results favor re-entry as the mechanism of tachycardia in group A patients. In group B abnormal automaticity seems more likely. In one patient with chronic recurrent VT the arrhythmia could be terminated by a single atrial premature beat. In a patient with Wolff-Parkinson-White syndrome and old myocardial infarction, VT could be initiated by a single atrial premature beat. One patient was studied while having VT during acute myocardial infarction and again five weeks later. In the acute phase of myocardial infarction no evidence for re-entry could be obtained; during the second study, however, ventricular tachycardias could be initiated and terminated by a single ventricular premature beat fulfilling the criteria of re-entry.