The effect of posture on the response to atrioventricular synchronous pacing in patients with underlying cardiovascular disease.

In order to determine whether the hemodynamic benefit of atrioventricular synchronous pacing is maintained in the upright position, 14 patients with dual chamber pacemakers were paced in VVI mode and DDD mode in both the supine and standing position. The hemodynamic response was assessed by measuring the velocity time integral derived from the pulsed-wave Doppler signal in the left ventricular outflow tract during VVI pacing and dual chamber pacing at three different AV delays (125, 200, 250 ms). In the supine position, the velocity time integral during VVI pacing was 14.6 +/- 3.0 cm and this increased during DDD pacing at all three AV delays (17.7 +/- 3.3, 17.9 +/- 3.0, 17.5 +/- 3.5 cm). In the upright position, the velocity time integral during VVI pacing was 12.9 +/- 3.5 cm and this increased with DDD pacing (15.5 +/- 3.3, 15.1 +/- 4.0, 15.1 +/- 3.9 cm). It was concluded that although stroke volume decreases when assuming the upright position, the beneficial response to dual chamber pacing is maintained and equals that observed in the supine position.