Atrial sensing performance of a single-lead VDD pacing system during physical activities

This study was undertaken to evaluate the atrial sensing performance of a s ingle-lead atrials synchronous-ventricular pacing system during various phy sical activities on late follow-up. Fourteen patients (mean age 55 +/- 17 y ears) with a third-degree or high-degree atrioventricular block and normal sinus node function were treated with the single-lead Thera VDD (Medtronic, Inc. Minneapolis, MN) pacemaker system. Mean P-wave amplitude at implantat ion was 3.2 +/- 1.3 mV. To assess the VDD system performance, P-wave amplit udes during various physical maneuvers (supine, sitting, deep breathing, st anding, and exercise; respectively) were measured and atrial sensing was ev aluated at a mean follow-up of 11 +/- 4 months. During deep breathing, mini mum and maximum P-wave amplitudes (0.8 +/- 0.7, 1.2 +/- 1.0 mV, respectivel y) were found to be significantly lower than the standing position (minimum , 1.1 +/- 0.9, maximum, 1.4 +/- 1.1 mV P = .02 in both). No significant dif ference was found during other physical maneuvers. During the testing maneu vers, atrial undersensing was observed in 8 patients (57%) at the nominal a trial sensitivity of 0.5 mV. After increasing the atrial sensitivity (0.25 mV), no sensing failure was observed in these patients. It has been conclud ed that Medtronic Thera VDD system is a safe and reliable device with an ea sy implantation technique providing effective atrioventricular synchronizat ion. The sensing problems, which may occur on late follow-up, can be correc ted successfully by reprogramming. To achieve an optimal atrial sensing fun ction in patients with a single-lead VDD pacing, we recommend that the atri al sensing capability should be examined in various physical maneuvers.