Silent left ventricular dysfunction during exercise after coronary artery bypass surgery

Serial changes in left ventricular function during exercise were assessed by radionuclide continuous ventricular function monitoring in 80 patients undergoing coronary artery bypass surgery before and after operation. This monitor records serial beat by beat radionuclide and electrocardiographic data and calculates the left ventricular ejection fraction every 20s. The profiles of ejection fractions during graded bicycle exercise were divided into 4 types. In type A, the ejection fraction continued to increase. In type B, the ejection fraction initially increased but decreased in late exercise. In type C, the ejection fraction did not change. In type D, the ejection fraction continued to decrease. Type A is considered to be the normal response to exercise and types B, C and, D are considered to be abnormal responses. Before operation, 8 patients showed type A, 21 type B, 13 type C, and 38 type D. After operation, 53 patients showed type A, 16 type B, 8 type C, and 3 type D. The mean ejection fraction decreased with exercise from 53% +/- 11% to 47% +/- 11% before surgery, but increased with exercise from 55% +/- 10% to 64% +/- 14% after surgery. During postoperative exercise, no patient developed chest pain but 19 patients showed a decrease in the ejection fraction in early or late exercise. A decrease in the ejection fraction is an earlier indicator of myocardial ischaemia than angina or electrocardiographic changes. Silent left ventricular dysfunction during postoperative exercise was considered to reflect myocardial ischaemia resulting from occluded grafts, ungrafted coronary arteries, or inadequate perfusion by arterial grafts. The radionuclide continuous ventricular function monitor can detect silent left ventricular dysfunction after coronary artery bypass surgery.