SUMMARY Changes in myocardial perfusion and left ventricular function were evaluated pre-and postoperatively (3-6 months) in 14 patients with unstable angina who underwent coronary artery bypass surgery. Perfusion was studied with intracoronary and intragraft injections of radiolabeled macroaggregated albumin particles. Of 20 abnormal perfusion areas identified preoperatively, 13 demonstrated improved perfusion postoperatively. Segmental analysis of the left ventriculogram demonstrated improved wall motion in 29 abnormally contracting segments; 18 normalized. Areas which showed improvement of left ventricular perfusion were invariably associated with improvement of left ventricular wall motion. Five patients showed improvement in perfusion and contraction in areas of apparent old myocardial infarction.Thirteen of the 14 patients had significantly less angina whether or not there was evidence of improved perfusion. However, only those patients who demonstrated improved perfusion had a significant improvement in their treadmill exercise tolerance postoperatively. Thus, patients with unstable angina have perfusion defects which may be reversed as a result of saphenous vein graft surgery. Reversal of these perfusion abnormalities results in improved left ventricular performance and better exercise tolerance postoperatively.CORONARY ARTERY BYPASS SURGERY has an important and widespread role in the treatment of coronary artery disease.1'3 Of particular significance to many investigators is the preoperative detection of ischemic, but viable, myocardium and the ultimate effects of revascularization upon improvement of left ventricular perfusion and function.4-5 Perhaps this problem is best exemplified in those patients with unstable angina who have poorly contracting areas of the ventricle which are being supplied by vessels with highly stenotic lesions. The recent reports of resting perfusion abnormalities in this group of patients6' 7 further raises the question whether these areas represent viable (reversibly damaged) myocardium or nonviable (irreversibly damaged) myocardium.Various techniques using intervention ventriculography have been used to identify potentially viable myocardium.8320 Another method used to differentiate between viable and nonviable myocardial tissue is the use of direct intracoronary instillation of radiolabeled, macroaggregated albumin particles.7 21-26Since these particles lodge in the coronary microcirculation, the presence of radioactivity throughout the myocardium has been equated with tissue viability. ticularly, the relationship of perfusion defects to segmental left ventricular contraction abnormalities and their potential for reversibility after coronary artery bypass surgery has not been demonstrated. If such perfusion defects do not always imply infarction, myocardial revascularization would be expected to correct the ischemia by improving blood flow, resulting in concomitant relief of angina and improvement of left ventricular performance. There have been relatively few studies exam...

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