Parasystole associated with fixed coupling ventricular ectopic activity.

In 5 patients ventricular parasystole and fixed coupling ectopic beats were recorded. In two cases ventricular parasystole and bigeminism acted intermittently. In one case the spontaneous transition from ventricular parasystole into parasystolic tachycardia with "reverse coupling" and finally to ventricular bigeminy could be illustrated. In all these cases ventricular parasystole and fixed coupling extrasystolic activity seems to be a close related mechanism. In other two cases there was a mathematical relationship between the sinus and parasystolic discharge rate which explained the periodic fixed coupling of ectopic beats. In one of these cases His bundle electrography was helpful in documenting the ventricular origin of ectopic beats.