Direct recording of concealed ventricular extrasystoles producing pacer inhibition

Abstract

We report a case of concealed extrasystoles recorded from a pacing lead. The concealed extrasystoles were observed with right ventricular pacing, biventricular unipolar, and biventricular bipolar pacing. The simultaneous surface EKG did not show manifest ventricular extrasystoles with the concealed intracardiac potentials. This case highlights a cause of oversensing that has been theoretically reported in the literature but never directly observed.