[Atrial sensing by a new VDD pacemaker].

VDD stimulation is an alternative to DDD pacing due to the possibility of p-wave synchronous ventricular pacing without the need of an atrial lead. Mainly, the reliability of the system depends on the atrial sensing. In 22 patients the intraoperative atrial amplitude and, postoperatively, the atrial sensing threshold were measured. Furthermore, the stability of the atrial sensing threshold during follow-up was proven. The mean atrial amplitude was intraoperative by 2.4 +/- 1.2 (1.0-6.8) mV. The measurement of the atrial sensing threshold in the first 5 postoperative days showed a mean value of 1.02 +/- 0.49 (0.3-1.6) mV. The measurements of the mean atrial sensing threshold after 30, 90, and 180 days showed no statistical differences. Intraindividual variance was shown in 17/20 patients (0.55 +/- 0,42; 0.15-1.05 mV). Seventeen of the 22 patients were programmed with an atrial sensing threshold of 0.3 mV. In five patients the atrial sensing threshold was programmed at less than 0.3 mV in order to reach a twofold atrial sensitivity. Despite a programmed atrial sensitivity of 0.1 mV and isometric conditions no atrial oversensing occurred. The postoperative atrial sensing thresholds of the VDD system investigated were significantly lower than the intraoperatively measured atrial amplitudes. The mean atrial sensing threshold did not change during the follow-up period. The variation which did occur was within individual variation at different return visits.