Some types of ventricular tachycardia(VT), so called verapamil-sensitive ventricular tachycardia, occur in healthy young people without organic heart disease. The mechanism of the above VT is not established yet. The most possible mechanism is a triggered activity but reentry is also possible mechanism. We studied the possible mechanism and the eletrophysiologic properties of the verapamil-sensitive VT in 6 patients.

The patients included in this study were patients with documented ventricular tachycardia response to intravenous verapamil and complete RBBB morpholgy. As noninvasive tests, treadmill test, echocardiography and MUGA scan were performed and endomyocardial biopsy was perfomed in all patients in all patients and in patients with inducible VT, the electrophysiologic study was repeated on next day. The response to various antiarrhythmic agents was also studied.

Total studied patients were 6(M : F=5 : 1, mean age=22). The noninvasive tests were normal in all patients and the VT was not induecd during treadmill test. The average cycle length of VT was 370msec and the 12-lead ECG during VT showed complete RBBB. The endomyocardial biopsy showed a mild focal infiltration of inflammatory cell in one patient and moderate small vessel vasculosclerosis in one patient. The clinical VT was induced in 5 patients by programmed electrical stimulation(PES). VT was induced in 5 by ventricular stimulation and in 1 by atrial stimulation. The induction and termination modes changed in 4 of 5 on next day. The cycle length dependency of PVC could be measured in 3 patients and the relationship was same direction in 2 patients and inverse direction in another patient. Intravenous procainamide was effective in 2 of 4 patients and IV adenosine was effective in 1 of 5 patients and IV propranolol was not effective in all 3 patients.

The verapamil-sensitive ventricular tachycardia is a unique VT showing characteristics of both reentry and triggered activity but in one patient of our study, the most possible mechanism is triggered activity. A further cellular electrophysiologic study is needed for the genesis of verapamil-sensitive ventricular tachycardia.