Left ventricular volumes and function during atrial pacing in coronary artery disease: A radionuclide angiographic study

This study set out to determine the pathophysiologic changes in the left ventricle during atrial pacing in 22 patients with coronary artery disease. Graduated right atrial pacing to a rate of 160 beats/min, or the induction of angina pectoris or significant ST depression was undertaken. Ventricular volumes were measured at rest and at rates of 100, 120, 140 and 160 beats/min using radionuclide angiography. The volumes at a pacing rate of 100 beats/min were used as a reference standard (100%). In the 22 patients with coronary artery disease, left ventricular end-diastolic volume decreased from 118 ± 3% at rest to 80 ± 5% at a rate of 160 beats/min; stroke volume from 121 ± 3% to 54 ± 5%; and ejection fraction (EF) from 49 ± 3% to 37 ±5%. End-systolic volume decreased from 118 ± 4% at rest, reached its minimal value of 94 ± 5% at a rate of 120 beats/min and then increased slightly to 106 ± 9% at 160 beats/min. Cardiac output and blood pressure did not change significantly. Compared to the control group of 10 normal subjects, the patients had a significantly smaller decrease in end-diastolic volume and end-systolic volume than in normal control subjects. EF in the normal subjects did not change. Blood pressure, cardiac output and stroke volume were similar in both groups. Atrial pacing tachycardia induced reversible ventricular dysfunction with a decrease in EF. Stroke volume was maintained because of relative ventricular dilatation.