Unexpected loss of bipolar lead function associated with lead connection design in dual chamber pacemakers.

Unexpected loss of bipolar pacing function can occur in Guidant VIGOR dual chamber pacemakers with QC2 (Quick Connect) headers. In a retrospective review of 305 implanted patients, 23 exhibited unexpected loss of bipolar pacing lead function from < 1 to 51 months postimplant. Atrial lead problems were seen in 17 patients and ventricular lead problems in 6 (P < 0.05 atrial vs ventricular). Significant symptoms developed in six patients including two with syncope as a result of noncapture. No significant change in bipolar sensing function was seen. Reprogramming devices to the unipolar mode restored appropriate pacing thresholds and lead impedance. The changes in bipolar lead function are likely caused by failure of the QC2 header lead connection system over time.