Short-term hemodynamic effects of DDD pacing from ventricular apex, right ventricular outflow tract and proximal septum.

Recently, short-term hemodynamic benefits of right ventricular outflow tract (RVOT) or proximal septum (His bundle area) pacing have been reported in comparison with traditional apical stimulation in preliminary investigations. The purpose of the present study was to compare the hemodynamics obtained during DDD pacing from ventricular apex, RVOT and proximal septum in patients with normal left ventricular function. A simultaneous hemodynamic and Doppler-echocardiographic study was performed in 21 patients (age 67 +/- 7 years) with sick-sinus syndrome (8 pts) or 2nd-3rd degree atrioventricular (AV) block (13 pts). The three stimulation sites were randomized and pacing was applied at an identical rate (84 +/- 5 beats/min) and at a constant AV delay (150 ms). Electrocardiographic, hemodynamic and Doppler-echocardiographic investigations were performed during stimulation from each site. The QRS duration did not show significant differences during DDD pacing from ventricular apex, RVOT and proximal septum. The hemodynamic measurements (systemic pressures, mean pulmonary wedge pressure, pulmonary pressures, right ventricular end-diastolic pressure, mean right atrial pressure, cardiac index, systemic vascular resistance and arteriovenous O2 difference) did not show significant differences during pacing from the three sites. Moreover, no significant differences were observed for the Doppler-echocardiographic measurements of systolic function (aortic stroke distance, left ventricular ejection fraction) and diastolic function (isovolumetric relaxion time, mitral E/A ratio, deceleration rate of the E wave). The results suggest that in patients with normal left ventricular function DDD pacing from RVOT or proximal septum does not improve cardiac function with regard to apical pacing.