ELECTROCARDIOGRAPHIC PATTERNS RELATIVE TO INITIATING MECHANISMS OF EXERCISE-INDUCED VENTRICULAR-TACHYCARDIA

The initiating mechanisms of exercise-induced ventricular tachycardia were studied in a population of 5842 patients who performed 9064 bicyc le exercise tests. Sixty (1%) patients had 194 episodes of ventricular tachycardia during the test. Forty-two percent of these occurred duri ng exercise and 58% during recovery. Two different initiating electroc ardiographic patterns were observed. In 17 (28%) patients ventricular tachycardia was initiated by a short-long-short sequence of R-R interv als (group 1). Thirty-eight (63%) patients did not have this pattern o f interval changes preceding ventricular tachycardia (group 2). Five ( 8%) other patients showed both patterns. The clinical characteristics of the groups were different for angina and cardiomyopathy but not for previous myocardial infarction. In group 1 ventricular tachycardia wa s related to recovery (76%; p < 0.05). In group 2 tachycardia occurren ce was equally divided between exercise and recovery. The electrocardi ographic differences suggest that different initiating mechanisms are involved in the development of exercise-induced ventricular tachycardi a. The present findings may enhance aimed drug therapy in ventricular tachycardia.