A unique pulse generator safety feature for bipolar lead fracture.

In this report, we describe two pacemaker dependent patients with outer-coil fractures in their bipolar ventricular leads who averted potentially catastrophic consequences because of a new safety feature incorporated into their pulse generators (Intermedics Cosmos II, model 284-05). Both patients were asymptomatic; the malfunctions were discovered at routine pacemaker evaluation. Magnet application resulted in symptomatic loss of ventricular capture. In each instance, the pulse generator detected an outer-coil fracture and reprogrammed itself from bipolar DDD to unipolar DOO pacing to prevent loss of capture. Subsequent lead replacement resulted in resumption of normal function. We suggest that this feature be incorporated into all devices with programmable polarity.