The response of left ventricular function and size to atrial pacing, volume loading and afterload stress in patients with coronary artery disease.

Abstract

To assess the response of left ventricular function and size to volume loading, atrial pacing and afterload stress, 35 patients were studied using equilibrium radionuclide angiography. All subjects had coronary heart disease, evidenced by contrast angiography or previous myocardial infarction. Patients [15] received 500 ml of normal saline given as 2 rapid 250-ml infusions. Ejection fraction increased after the 2nd infusion (0.49 to 0.55 P < 0.05), as did end-diastolic volume (P < 0.05), but there was little change in end-systolic volume or the ratio of systolic blood pressure to end-systolic volume. Eight patients were subjected to phenylephrine afterload stress, with a mean elevation of systolic blood pressure of 44.6 .+-. 12 mm Hg (P < 0.01 vs. rest). Ejection fraction declined (0.52 .+-. 0.1 to 0.41 .+-. 0.13, P < 0.01); end-diastolic and end-systolic volumes increased (P at least < 0.01). The ratio of systolic pressure to end-systolic volume decreased (2.31 .+-. 1.64 to 1.46 .+-. 0.67 mm Hg/ml, P < 0.05). Twelve patients underwent atrial pacing (from 80-130 beats/min), resulting in a decrease in ejection fraction, a decrease in end-diastolic and end-systolic volumes (P < 0.05) and an increase in the pressure-volume ratio (2.00 .+-. 0.30 to 2.45 .+-. 1.02 mm Hg/ml, P < 0.05). Alterations in loading conditions apparently affect indexes of left ventricular performance. The ejection fraction is reduced by elevations in blood pressure and increased by volume infusion, but appeared reduced by atrial pacing, probably due to the offsetting changes in heart rate and preload. The pressure-volume ratio did not change with volume loading, decreased with afterload stress and increased with atrial pacing. Equilibrium radionuclide angiography can be used to assess noninvasively the effects of physiologic and pharmacologic interventions on left ventricular performance in patients with coronary heart disease.