Optimal atrioventricular delay in physiological pacing determined by Doppler echocardiography.

Our study included eight patients with physiological pacemakers programmed to the VDD mode. The blood velocity in the aortic root was determined by Doppler echocardiography. Changes in the integral of maximum velocity reflect stroke volume changes. The Doppler probe was placed and held in the suprasternal position while programming the pacemakers from the VVI to all available AV delays in the VDD mode; the heart rates were nearly constant. Stroke volumes were highly dependent on changes of the AV delay; the optimum AV delay varied considerably from patient to patient. These changes were more pronounced in the patients with left ventricular strain due to aortic valve disease than in the patients with isolated conduction defects.