Insulation failure with bipolar polyurethane pacing leads

Between October, 1981, and April, 1983, 200 pacemakers were inserted at Rhode Island Hospital. Forty-five bipolar polyurethane leads (Medtronic 6972) were positioned in the right ventricle. Three (6.6%) of these leads presented 15 to 18 months post-implant with insulation failure. The manifestation was inappropriate inhibition of the pacemaker. No obvious cracking was visible on X-ray or during surgery. All the leads had low impedance, indicative of insulation failure.