BRADYCARDIA-DEPENDENT AND TACHYCARDIA-DEPENDENT TERMINATION OF VENTRICULAR BIGEMINY - MECHANISM OF VENTRICULAR EXTRASYSTOLES WITH FIXED COUPLING

Fourteen men with intermittent ventricular bigeminy were selected for this study because coupling intervals of the extrasystoles were consid erably long and usually fixed, and bradycardia-dependent (10 cases) an d/or tachycardia-dependent (12 cases) termination of bigeminy occurred . In all cases, when the heart rate ranged between two certain values, ventricular bigeminy with fixed-coupled extrasystoles was sustained. In all cases showing bradycardia-dependent termination, bigeminy was s uddenly terminated with no changes in coupling of the preceding extras ystoles when the heart rate was decreased below a certain lower value. In all cases showing tachycardia-dependent termination except one, wh en the heart rate increased beyond a certain higher value, coupling in tervals gradually lengthened until bigeminy was terminated. These find ings strongly suggest the possibility that, in a considerably large nu mber of clinical cases, ventricular extrasystoles with fixed coupling are caused by longitudinal dissociation of conduction in the reentrant pathway of extrasystoles.