Stability of atrial sensing and pacing after dual chamber pulse generator implantation

The continued efficacy of dual chamber pacing is predicated on the stability of both atrial and ventricular electrodes. The introduction of the tined atrial J lead has decreased the incidence of atrial lead dislodgment, allowing for continued effective sensing and pacing. To study the evolution of atrial pacing and sensing threshold, 54 patients with identical pulse generators and atrial electrodes were evaluated for 58 +/- 29 weeks (mean +/- SD). Immediately after pacemaker implantation in 39 patients, the amplitude of the atrial signal was measured by programming the pulse generator to the lowest sensitivity that assured pacing in the atrial synchronous mode. Three levels of atrial sensing were possible: high (0.5 mV), intermediate (1.3 mV) and low (2.5 mV) sensitivity. Three patients had a high, 16 patients had a medium and 20 patients had a low atrial sensitivity. The P wave amplitude and slew rate measured on a physiologic recorder did not differ significantly between the latter two groups. The atrial charge threshold increased from 1.8 +/- 1.3 microcoulombs (microC) to a maximal value of 2.5 +/- 1.3 microC, 3 days to 1 week after implantation (p = 0.02). This remained elevated for 1 to 3 months (p = 0.05) and then decreased, remaining stable over the ensuing year. The atrial sensitivity for the group with noninvasive measurement did not change significantly, although there was considerable patient variation. For 54% of the patients, atrial sensing remained stable or improved. In 26% of the patients, further programming to higher sensitivity settings ws required. In the remaining 20% of the patients, the atrial sensitivity setting fluctuated.(ABSTRACT TRUNCATED AT 250 WORDS)