The hemodynamic effects of ventricular pacing with and without atrioventricular synchrony in patients with normal and diminished left ventricular function.

The relative hemodynamic effects of heart rate, inotropic state, and atrioventricular (AV) synchrony during ventricular pacing were evaluated in 10 patients with normal left ventricular ejection fraction (LVEF) (0.66 +/- 0.07, mean S.D.) and in eight patients with a diminished LVEF (0.34 +/- 0.18). Hemodynamics were measured at AV intervals of 130, 0, and -130 msec during ventricular pacing at a baseline rate that was 10 pulses/min greater than the resting heart rate, at 130 pulses/min alone, and at 130 pulses/min during continuous intravenous infusion of dobutamine. During baseline ventricular pacing and during ventricular pacing at 130 pulses/min with and without dobutamine, both groups of patients had a significant decrease in cardiac index, stroke volume index, and stroke work index when the AV pacing interval was decreased from 130 to 0 msec. The observed decrease in these three hemodynamic variables was similar when patients with diminished LVEF were compared to patients with normal LVEF. No further significant decrease in cardiac index, stroke volume index, and stroke work index occurred in either group when the AV interval was changed from 0 to -130 msec during baseline ventricular pacing or during ventricular pacing at 130 with and without dobutamine. Beneficial hemodynamic effects occur during ventricular pacing when AV synchrony is maintained at resting heart rates and during increases in heart rate and inotropic state in patients with normal and diminished LVEF.