Periodic pacemaker spike attenuation with preservation of capture: an unusual electrocardiographic manifestation of partial pacing electrode fracture.

This report describes the electrocardiograms of a patient with an intermittent electrode fracture presenting with periodic attenuation of the pacemaker spike without loss of ventricular capture. There was infrequent prolongation of the spike-to-spike interval probably because the pulse generator interpreted random false signals as interference and reverted to its fixed-rate mode. These observations add to the spectrum of electrocardiographic abnormalities of electrode malfunction.