Intermittent and arrhythmic "runaway" pacemaker.

An unusual case of intermittent and arrhythmic runaway pacemaker is described. The malfunction was detected during implantation, at which time it caused ventricular fibrillation in the patient in whom it was implanted. The authors wish to emphasize the necessity of accurate pacemaker testing in the factory and the operating room, and to stress the importance of manufacturing pacemakers unable to emit a high number of impulses, even in the presence of a faulty circuit component.