Idioventricular parasystolic rhythms

A description is given of the electrocardiograms of three subjects with artificial demand pacemakers in whom no inhibition of the idioventricular rhythms occurs, thus causing unusual relationships between the artificial and the spontaneous rhythms. The latter are protected and therefore appear to be parasystolic. In the first two cases, interpolated artificial beats are inscribed in the spontaneous rhythm. In the third case, the spontaneous parasystole is intermittent and alternates with concealed extrasystolic beats originating in the same focus.