The effect of aortocoronary bypass grafts on myocardial blood flow reserve and treadmill exercise tolerance.

Twenty-five patients had myocardial blood flow reserve determinations (percentage increase in myocardial blood flow with stress), treadmill exercise tests and coronary and bypass cineangiography preand postaortocoronary bypass surgery. Twenty of the patients had the postoperative studies performed three months after operation, three at two months and two at five and six months, respectively. Eleven of the 25 patients had all significant coronary artery obstructions (75%1 or greater) bypassed and all grafts were open at the time of restudy. Preoperatively, blood flow reserve had been abnormal in nine and all had positive treadmill tests. Postoperatively, all eleven patients had normal myocardial blood flow response to stress and treadmill tests were negative in ten (one patient was not restudied on the treadmill). In six patients, no patent grafts could be demonstrated. These patients continued to show abnormal blood flow reserve and positive treadmill studies. Eight of the 25 patients had partial revascularization in that some grafts were open, some closed, and