Abstract
We investigated the correlation of atrial dipole position and the ability to pace the atrium. We performed electron beam tomography (EBT) in ten patients implanted with a single-pass lead for permanent VDD pacing (Medico Phymos 830-s lead). The distance from the proximal electrode to the atrial free wall was measured. Simultaneous with the EBT, we evaluated atrial pacing thresholds. The mean atrial thresholds at 12months of follow-up were 0.3±0.2 ms at 5 V in 4 patients (low threshold group; LTH) and 1. 3±0.5ms at 5 V in the remaining patients (high threshold group; HTH). In the LTG, the mean distance to the free wall of the right atrium from the proximal electrode was 3.8±0.7mm and that of the HTH was 7.4±2.6mm. In conclusion, single-pass lead DDD pacing by a Medico 830-s lead enabled effective and reliable atrial pacing clinically if the proximal electrode was positioned within 4mm of the atrial free wall. Thus, atrial pacing was achieved when the proximal electrode was in direct contact or very close proximally to the free wall of the right atrium, while single-pass lead DDD pacing was extremely difficult under the condition that the proximal electrode was free floating.
