DDD and single-lead VDD pacing: Evaluation of atrial signal dynamic changes

Background: Single-lead VDD pacing systems are an alternative to convention al DDD pacemakers in patients with atrioventricular (AV) block and normal s inus function. Hypothesis: The aim of this study was to assess changes of P-wave amplitude occurring in dynamic conditions in two groups of patients with a single-le ad VDD and with a DDD pacing system, respectively. Methods: Twenty-eight patients with second- or third-degree AV block and no rmal sinus function were enrolled prospectively into the study. Seventeen p atients were implanted with a single-lead VDD pacing system and 11 with a D DD pacemaker. Patients were evaluated at 3 months tall patients) and at 6 m onths (26 patients) at supine and in dynamic conditions (postural changes, hyperventilation, and during exercise). Results: Mean P-wave values at supine were 1.92 +/- 1.10 mV at 3 months and 1.76 +/- 1.01 mV at 6 months for VDD systems, and 4.63 +/- 2.18 mV at 3 mo nths and 4.58 +/- 2.80 mV at 6 months for DDD pacemakers. In dynamic condit ions, P-wave amplitude changes compared with supine condition ranged betwee n -74 and +226% in VDD, and between -53 and +138% in DDD; however P-wave am plitudes showed no significant changes compared with baseline. Moreover, ch anges in atrial signal amplitudes did not occur randomly, and in both syste ms P-wave amplitudes remained significantly correlated with supine values. Conclusions: A wide range of P-wave amplitude variations occurs in differen t postural conditions or during exercise, both with single-lead VDD and DDD pacing systems. However, with appropriate programming of atrial sensitivit y based on supine values, constant atrial tracking can be maintained.