Long-term assessment of unipolar and bipolar stimulation and sensing thresholds using a lead configuration programmable pacemaker.

Acute and long-term pacing thresholds were measured prospectively in 74 patients with a unipolar/bipolar multiprogrammable pacemaker. At implantation, mean current threshold was 0.48 +/- 0.16 mA with unipolar mode and 0.55 +/- 0.16 mA bipolar mode (p less than 0.01). R wave amplitude at implantation was 7.78 +/- 2.4 mV with unipolar and 7.67 +/- 2.1 mV in bipolar mode (p = NS). During long-term follow-up (mean 9.3 months; range 3 to 24), no clinically significant differences in pacing or sensing thresholds were observed between bipolar and unipolar configurations. Lead configuration was changed 23 times in 11 patients. Symptomatic myopotential inhibition was corrected in two patients by reprogramming to the bipolar pacing mode. High thresholds and loss of capture were corrected in two patients by reprogramming to the unipolar pacing mode. The remaining configurational changes were made for improved sensing or pacing thresholds. This study documents, in a large group of patients, the equivalence of long-term unipolar and bipolar pacing and sensing thresholds and, in addition, demonstrates that lead configuration programmability offered some advantage in a subgroup of patients and may have prevented reoperation in five patients.