EDITORIALS
Coronary Controversy
S
ome controversies about coronary bypass operations have been resolved: the feasibility of operating at low risk is established, the potential of operation to eliminate the distress of angina pectoris is generally accepted, and the probability of operation prolonging life in selected patients is increasingly being documented and applied in clinical practice. Controversy now seems to be centering about which surgical techniques give the best results. Among different techniques, preferential use of an internal mammary artery pedicle rather than a saphenous vein segment is conspicuous. Two papers in this issue reflect a peak of interest in this question of choice of techniques. Grondin and his colleagues (p 605, this issue) report on two groups of patients evaluated angiographically early and one year after operation, one of which had saphenous vein grafts studied (83/100 patients) and the other, internal mammary artery pedicle grafts (37/40 patients, 38 grafts). Little difference in late patency or late narrowing of grafts was found between the two groups. However, it was noted that the early study of internal mammary anastomoses showed one graft to be closed, nine to be stenotic at the anastomosis, and three coronary arteries to be occluded just beyond the anastomosis -i.e., in 13 of 38 grafts the technique was imperfect. Many aspects of operation (preparation of grafts, choice of site for arteriotomy, exposure, illumination, magnification) are so important that deficiencies in their execution can mask differences in biological suitability of bypass conduits. Grondin’s analysis of data is careful; he comments on the importance of the mammary artery being larger than the coronary segment to which it is sewn. Yet in only 13 of 38 grafts was the mammary artery larger than the coronary segment to which it was anastomosed. It is unlikely that the anatomy of the mammary artery is different in Montreal and New York; it is more likely that technique of mobilization accounts for the small size of the mammary arteries used in the Montreal series. The artery should always be mobilized to the top of the first rib to assure that all side-branches have been divided and to facilitate use of the most proximal possible site for anastomosis. Deliberate mobilization is required to obtain an arterial graft wider than 2 mm and of greater diameter than the coronary artery to which it is anastomosed. Maximum exposure, careful selection of site for ar-
7 16
THE ANNALS OF THORACIC SURGERY
Editorial teriotomy, and optimal illumination and magnification are necessary to prevent occlusion of coronary arteries distal to anastomoses; such occlusions were seen in postoperative angiograms of 3 of the 37 patients. Three other failures of arterial anastomoses were suspected in the operating room because of inadequate heart action. They were corrected by reconstruction with saphenous vein grafts and may also have been due to faulty technique rather than inadequacy of the mammary artery. Mobilization of the mammary artery is more difficult than removal of a saphenous vein segment, and because of greater friability, suture technique requires more facility with mammary arteries than with saphenous vein grafts. One benefit of the arterial graft is minimizing of biological change after operation. All vein grafts thicken in response to arterial pressure. This resulted in stricture being recognized in 13% of Grondin’s series. Graft stricture can be minimized by sewing artery to artery. Also, in most series, overall late patency has been higher following arterial anastomosis than after saphenous vein grafting. The paper by Flemma and his colleagues (p 619, this issue) comments that late patency is not a sufficient criterion of success and attempts to compare hemodynamic differences between mammary artery and saphenous vein grafts by studying pressures and flows in 14 patients who underwent “vein-mammary additive graft” procedures. The hemodynamic values reported represent a new low in flow following mammary artery anastomosis. It seems likely that flow through the mammary artery was depressed as a result of anastomosis to a saphenous vein segment which, being larger than the mammary artery, caused outflow turbulence and thereby resistance to flow. Similar reservations must be observed in considering Flemma’spressure data. Pressure measured in a large reservoir interposed between the end of a mammary artery and the inlet to a coronary segment cannot be considered a valid representation of “driving pressure” for flow through an internal mammary artery graft. Flemma’s interpretation of these data prompts him to advise against mammary anastomoses to coronary arteries with high flow capacity. His advice, based on a small series of observations of dubious relevance, is in contrast to my own protracted clinical experience [2] and that of others such as Geha and colleagues [ l ] and Kay and associates [3]. I have now performed internal mammary anastomosis to the left anterior descending coronary artery in 800 patients, most of whom had saphenous vein grafts to other coronary arteries. Postoperative status (frequently including treadmill testing) has been evaluated annually. Most patients who encountered clinical difficulty have undergone repeat angiography. Review of annual clinical reports and of more than 100 postoperative angiograms has indicated that mammary-coronary anastomosis was the most reliable of coronary bypass procedures. It is important to acknowledge that the performance of coronary bypass operations is as much art as science. The choice of artery or vein graft is not sufficient to produce excellent results. This choice must be accompanied by optimal coordination and execution of all aspects of the operation. The mammary
VOL. 20, NO. 6, DECEMBER, 1975
717
Editorial
artery graft is more demanding than the saphenous vein graft. Each surgeon’s answer to the question of which is the best method of operation will be helpful to his patients only as it is resolved by him. GEORGE E.
GREEN,
M.D.
1090 Amsterdam Ave. New York, N.Y. 10025
References 1. Geha, A. S., Krone, R. J., McCormick, J. R., and Baue, A. E. Selection of coronary bypass: Anatomic, physiologic and angiographic considerations of vein and mammary artery grafts. J Thorac Cardaovasc Surg 70:414, 1975. 2. Green, G. E. Internal mammary artery-to-coronary artery anastomosis. Ann Thorac Surg 14:260, 1972. 3. Kay, E. B., Naraghipour, H., Beg, A., DeManey, M., Tambe, A., and Zimmerman, H. A. Internal mammary artery bypass graft -long-term patency rate and follow-up. Ann Thorac Surg 18:269, 1974.
718
T H E ANNALS OF THORACIC SURGERY
Coronary Controversy
S
ome controversies about coronary bypass operations have been resolved: the feasibility of operating at low risk is established, the potential of operation to eliminate the distress of angina pectoris is generally accepted, and the probability of operation prolonging life in selected patients is increasingly being documented and applied in clinical practice. Controversy now seems to be centering about which surgical techniques give the best results. Among different techniques, preferential use of an internal mammary artery pedicle rather than a saphenous vein segment is conspicuous. Two papers in this issue reflect a peak of interest in this question of choice of techniques. Grondin and his colleagues (p 605, this issue) report on two groups of patients evaluated angiographically early and one year after operation, one of which had saphenous vein grafts studied (83/100 patients) and the other, internal mammary artery pedicle grafts (37/40 patients, 38 grafts). Little difference in late patency or late narrowing of grafts was found between the two groups. However, it was noted that the early study of internal mammary anastomoses showed one graft to be closed, nine to be stenotic at the anastomosis, and three coronary arteries to be occluded just beyond the anastomosis -i.e., in 13 of 38 grafts the technique was imperfect. Many aspects of operation (preparation of grafts, choice of site for arteriotomy, exposure, illumination, magnification) are so important that deficiencies in their execution can mask differences in biological suitability of bypass conduits. Grondin’s analysis of data is careful; he comments on the importance of the mammary artery being larger than the coronary segment to which it is sewn. Yet in only 13 of 38 grafts was the mammary artery larger than the coronary segment to which it was anastomosed. It is unlikely that the anatomy of the mammary artery is different in Montreal and New York; it is more likely that technique of mobilization accounts for the small size of the mammary arteries used in the Montreal series. The artery should always be mobilized to the top of the first rib to assure that all side-branches have been divided and to facilitate use of the most proximal possible site for anastomosis. Deliberate mobilization is required to obtain an arterial graft wider than 2 mm and of greater diameter than the coronary artery to which it is anastomosed. Maximum exposure, careful selection of site for ar-
7 16
THE ANNALS OF THORACIC SURGERY
Editorial teriotomy, and optimal illumination and magnification are necessary to prevent occlusion of coronary arteries distal to anastomoses; such occlusions were seen in postoperative angiograms of 3 of the 37 patients. Three other failures of arterial anastomoses were suspected in the operating room because of inadequate heart action. They were corrected by reconstruction with saphenous vein grafts and may also have been due to faulty technique rather than inadequacy of the mammary artery. Mobilization of the mammary artery is more difficult than removal of a saphenous vein segment, and because of greater friability, suture technique requires more facility with mammary arteries than with saphenous vein grafts. One benefit of the arterial graft is minimizing of biological change after operation. All vein grafts thicken in response to arterial pressure. This resulted in stricture being recognized in 13% of Grondin’s series. Graft stricture can be minimized by sewing artery to artery. Also, in most series, overall late patency has been higher following arterial anastomosis than after saphenous vein grafting. The paper by Flemma and his colleagues (p 619, this issue) comments that late patency is not a sufficient criterion of success and attempts to compare hemodynamic differences between mammary artery and saphenous vein grafts by studying pressures and flows in 14 patients who underwent “vein-mammary additive graft” procedures. The hemodynamic values reported represent a new low in flow following mammary artery anastomosis. It seems likely that flow through the mammary artery was depressed as a result of anastomosis to a saphenous vein segment which, being larger than the mammary artery, caused outflow turbulence and thereby resistance to flow. Similar reservations must be observed in considering Flemma’spressure data. Pressure measured in a large reservoir interposed between the end of a mammary artery and the inlet to a coronary segment cannot be considered a valid representation of “driving pressure” for flow through an internal mammary artery graft. Flemma’s interpretation of these data prompts him to advise against mammary anastomoses to coronary arteries with high flow capacity. His advice, based on a small series of observations of dubious relevance, is in contrast to my own protracted clinical experience [2] and that of others such as Geha and colleagues [ l ] and Kay and associates [3]. I have now performed internal mammary anastomosis to the left anterior descending coronary artery in 800 patients, most of whom had saphenous vein grafts to other coronary arteries. Postoperative status (frequently including treadmill testing) has been evaluated annually. Most patients who encountered clinical difficulty have undergone repeat angiography. Review of annual clinical reports and of more than 100 postoperative angiograms has indicated that mammary-coronary anastomosis was the most reliable of coronary bypass procedures. It is important to acknowledge that the performance of coronary bypass operations is as much art as science. The choice of artery or vein graft is not sufficient to produce excellent results. This choice must be accompanied by optimal coordination and execution of all aspects of the operation. The mammary
VOL. 20, NO. 6, DECEMBER, 1975
717
Editorial
artery graft is more demanding than the saphenous vein graft. Each surgeon’s answer to the question of which is the best method of operation will be helpful to his patients only as it is resolved by him. GEORGE E.
GREEN,
M.D.
1090 Amsterdam Ave. New York, N.Y. 10025
References 1. Geha, A. S., Krone, R. J., McCormick, J. R., and Baue, A. E. Selection of coronary bypass: Anatomic, physiologic and angiographic considerations of vein and mammary artery grafts. J Thorac Cardaovasc Surg 70:414, 1975. 2. Green, G. E. Internal mammary artery-to-coronary artery anastomosis. Ann Thorac Surg 14:260, 1972. 3. Kay, E. B., Naraghipour, H., Beg, A., DeManey, M., Tambe, A., and Zimmerman, H. A. Internal mammary artery bypass graft -long-term patency rate and follow-up. Ann Thorac Surg 18:269, 1974.
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T H E ANNALS OF THORACIC SURGERY
