The effect of atrial contraction on left ventricular performance in valvular aortic stenosis.

SUMMARY The instantaneous response of the left ventricle to loss or recoverv of effective atrial contraction was studied in 12 patients with valvular aortic stenosis by producing A-V dissociation by electrical pacing of the ventricles so that some ventricular contractions were preceded by an effective atrial contraction while others were not. A conventional hydraulic formula relatinig size of the aortic valve orifice, pressure gradient, and flow was used to estimate beat to beat stroke volume. A properly timed atrial contraction augmented left ventricuilar performance in all patients, increasing stroke volume index from 14 to 55% (mean, 27%) anid stroke work from 17 to 85% (mean, 453%).