Quantitative assessment of myocardial performance and graft patency following coronary bypass with the internal mammary artery.

The internal mammary artery (IMA) has failed to gain wide acceptance as a bypass conduit because of doubt as to its effectiveness for myocardial perfusion. To assess the functional capacity of the IMA, we have evaluated 95 patients, receiving only an IMA graft, followed up to 58 months. Forty-five patients had preinfarction angina, 23 had unstable angina, six had acute myocardial infarction, 10 had paroxysmal ventricular tachycardia-fibrillation, seven had congestive heart failure, II had stable angina, and four were asymptomatic. Of 140 IMA grafts, 79 were to the left anterior descending coronary artery, 30 to the right coronary artery, two to the diagonal, 28 to the circumflex, and one to a perforator. Thirty-six patients had three vessel disease, 35 had two vessel disease, and 24 had one vessel disease. Systolic ejection fractions were less than 49 percent in 26 patients. Early postoperative studies were performed in 90 patients. Of 133 grafts studied, 132 were patent. Late studies in six patients showed enlargement of the IMA. The systolic ejection fraction improved in 32 patients, including 16 of 28 with values of less than 50 percent preoperatively. Of 119 treadmill stress tests performed, 71 produced normal responses at maximal load and 41 produced normal responses at submaximal load. No late graft closure has been documented. Ninety-five percent of the patients are free of angina, and all are free of arrhythmias. There have been seven late deaths, 3 to 22 months postoperatively, all occurring in patients with preoperative ejection fractions less than 48 percent. The results of this investigation indicate that the IMA is an excellent conduit for myocardial revascularization in all positions except the distal right coronary artery.