RADIOGRAPHIC ASSESSMENT OF ATRIAL DIPOLE POSITION IN SINGLE-PASS LEADVDD AND DDD PACING

Atrial electrode position was determined by radiographic analysis in 1 60 patients paced in single-lead VDD for second- or third-degree A-V b lock, implanted > 1 year with Phymos single pass leads and Phymos 3D p acemakers. The pacing lead features an atrial dipole with a 30-mm elec trode interspace. In 44% of patients, the upper atrial electrode was p ositioned within a band of 20 mm centered at the level of the superior vena caval insertion (junctional area) and was in the inferior vena c ava or in the atrium in 35% and 21% of cases, respectively lit spite o f these different dipole locations, all patients had stable atrium-dri ven pacing at routine follow-up visits. With the electrode in the junc tional area, unipolar stimulation of up to 5 V for 1 ms resulted in st able atrial capture in 63% and 59% of the patients in supine and uprig ht positions, respectively. With the electrode in the atrium, correspo nding success rates were 45% and 54%. In the atrium, however, the prev alence of diaphragmatic stimulation was significantly lower than at th e junction (10% vs 42% in supine position; 22% vs 47% upright). Though atrial sensing function proved adequate in a wide range of positions, these results suggest that the Phymos lead atrial dipole should be po sitioned within the atrium, as close as possible to the atrial wall, t o maximize the number of VDD patients who might benefit from single-le ad DDD pacing.