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Patency of internal mammary artery grafts in no-flow situations
J
THoRAc CARDIOVASC SURG
1987;93:62-4
Patency of internal mammary artery grafts in no-flow situations We report two cases in which an internal mammary artery graft was found to be OOnflDlCtiOnal in the early postoperative period, but repeat catheterization at 6 months revealed the graft to be patent. These two cases substantiate that closure of an internal mammary artery graft may be reversible.
Alejandro Aris, M.D., Xavier Borras, M.D., and Joaquim Ramie, M.D., Barcelona, Spain
Myocardial revascularization by means of the internal mammary artery has regained support because long-term patency and patient survival have been shown to be superior to that with coronary bypass using the saphenous vein.':' These results have been explained by the more physiologic characteristics of the artery compared with the vein. We present two cases in which an internal mammary artery graft failed to show any flow shortly after operation but was patent at 6 months. The physiologic basis for this phenomenon is discussed.
Case reports CASE 1. A 58-year-old male truck driver had a history of progressive angina. Medical therapy was ineffective. Coronary angiography showed an 80% stenosis of the left main trunk and critical stenosis of the circumflex and first diagonal arteries. Myocardial revascularization was performed, with an internal mammary artery graft to the anterior descending coronary artery and a sequential graft of the saphenous vein to the circumflex and first diagonal arteries. His recovery was uneventful, and before discharge he underwent angiography as a part of a protocol to study the effects of antiplatelet drugs on graft patency. The vein graft was patent, but the internal mammary artery showedinterruption of dye flow at the midportion (Fig. 1, A). Despite this finding, the patient had no symptoms, and because of his emotional status, and in agreement with his cardiologist,it was decided not to recommend another operation at that time. Postoperative progress was closely observed, and he resumed work after 2 months. A repeat angiographic study was performed 6 months after the operation. The lesion in the left
From the Cardiac Surgery and Hemodynamic Units, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain. Received for publication Jan. 14, 1986. Accepted for publication Feb. 18, 1986. Address for reprints: Alejandro Aris, M.D., Cardiac Surgery Unit, Hospital de la SantaCreu i Sant Pau,Av. San Antonio M. Claret 167,08025 Barcelona, Spain.
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main trunk had progressed and the internal mammary artery graft was patent (Fig. I, B). The patient has had no symptoms over the last 20 months despite his heavy work. CASE 2. A 52-year-old man with a history of myocardial infarction underwent cardiac catheterization because of intractable angina. The anterior descending coronary artery was completely occluded at its proximal third, and the circumflex artery had a critical stenosis at its origin. He underwent double coronary artery bypass: an internal mammary artery graft to the left anterior descending artery and a saphenous vein graft to the first marginal branch of the circumflex artery. The anterior descending artery was irregular, with a I mm diameter distal to the anastomosis. Recovery was uneventful, and the patient underwent repeat catheterization before discharge. Both grafts were occluded (Fig. 2, A). The patient refused a second operation, and was discharged taking nifedipine plus topical nitroglycerin. Repeat angiographic study 6 months later (part of the same protocol as in Case 1) showed that the internal mammary artery had regained patency (Fig. 2, B), although progression of the diseasein the grafted artery was evident.The patient is limited by exertional angina, but the extent of his atheromatosis precludes further operation.
Discussion The special characteristics of the internal mammary artery as a conduit for myocardial revascularization have been reported.v ' A decrease in flow may result from the steal phenomenon." spasm, or competitive flow. Dincer and Barner? reported a case similar to ours but with a longer interval. The internal mammary artery was open 1 week after operation, lost its patency at I year, but was open again, in association with progression of proximal coronary disease, at 5 years. They pointed out the possibility of competitive flow as the cause of the temporary closure of the graft. Our case reports support this contention. Close examination of the early postoperative film in Case 1 (Fig. 1, A) showed the end of the dye column to be pulsatile in a fashion that suggested retrograde flow in the internal mammary artery. The
Volume 93 Number 1 January 1987
Patency of internal mammary artery graft
63
Fig. 1. A, Selective angiogram of the left internal mammary artery shows interruption of flow at its rnidportion. B, Six months later the internalmammaryartery has regained patency, filling the leftanterior descending coronary artery (arrow).
anterior descending coronary artery was probably being perfused in part by the other grafts, and mostly through the left main trunk, which showed a significant but not critical lesion. With progression of the disease in the left main trunk, the internal mammary artery regained functional patency (it is safe to assume that it never lost its anatomic patency). In Case 2, the poor distal coronary bed was probably responsible for cessation of flow through the internal mammary artery. Development of collateral circulation or the vasoactive medication could decrease resistance, with reestablishment of flow at a later time. Early patency of the internal mammary artery reflects its ability to remain open in low-flow situa-
tions,!" an advantage not to be found with other kinds of conduits used for coronary bypass. The internal mammary artery is the graft of choice for myocardial revascularization. Care must be exercised to avoid any situation in which competitive flow may occur. Our two cases support the finding of Dincer and Barner" that "occlusion" of an internal mammary artery graft may be reversible. REFERENCES Tector AJ, Schmal TM, Janson B, Kallies JR, JohnsonG: The internal mammary artery graft. Its longevity after coronary bypass. JAMA 246:2181-2183, 1981 2 Grondin CM, Campeau L, Lesperance J, Enjalbert M,
The Journal of
64
Aris, Borras, Ramib
Thoracic and Cardiovascular Surgery
Fig. 2. A, Occlusion of the left internal mammary artery graft. B, Repeat angiogram at 6 months reveals a patent internal mammary artery that fills a diffusely diseased left anterior descending coronary artery (arrows).
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Bourassa MG: Comparison of late changes in internal mammary artery and saphenous vein grafts in two consecutive series of patients 10 years after operation. Circulation 70:Suppl 1:208-212, 1984 Okies JE, Page US, Bigelow JC, Krause AH, Salomon NW: The left internal mammary artery. The graft of choice. Circulation 70:Suppl 1:213-221, 1984 Kay HR, Korns ME, F1emma RJ, Tector AJ, Lepley D Jr: Atherosclerosis of the internal mammary artery. Ann Thorac Surg 21:504-507, 1976 Singh RN, Sosa JA: Internal mammary artery. A "live" conduit for coronary bypass. J THORAC CARDIOVASC SURG 87:936-938, 1984 Singh RN, Sosa JA: Internal mammary artery-coronary artery anastomosis. Influence of the side branches on
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surgical result. J THORAC CARDIOVASC SURG 82:909-914, 1981 Singh RN, Magovern GJ: Internal mammary graft. Improved flow resulting from correction of steal phenomenon. J THORAC CARDIOVASC SURG 84:146-149, 1982 Pelias AJ, Del Rossi AJ, Tacy L, Wolpowitz A: A case of postoperative internal mammary steal. J THORAC CARDIOVASC SURG 90:794-795, 1985 Dincer B, Barner HB: The "occluded" internal mammary artery graft. Restoration of patency after apparent occlusion associated with progression of coronary disease. J THORAC CARDIOVASC SURG 85:318-320, 1983 Barner HB, Swartz MT, Mudd JG, Tyras DH: Late patency of the internal mammary artery as a coronary conduit. Ann Thorac Surg 34:408-412, 1982
THoRAc CARDIOVASC SURG
1987;93:62-4
Patency of internal mammary artery grafts in no-flow situations We report two cases in which an internal mammary artery graft was found to be OOnflDlCtiOnal in the early postoperative period, but repeat catheterization at 6 months revealed the graft to be patent. These two cases substantiate that closure of an internal mammary artery graft may be reversible.
Alejandro Aris, M.D., Xavier Borras, M.D., and Joaquim Ramie, M.D., Barcelona, Spain
Myocardial revascularization by means of the internal mammary artery has regained support because long-term patency and patient survival have been shown to be superior to that with coronary bypass using the saphenous vein.':' These results have been explained by the more physiologic characteristics of the artery compared with the vein. We present two cases in which an internal mammary artery graft failed to show any flow shortly after operation but was patent at 6 months. The physiologic basis for this phenomenon is discussed.
Case reports CASE 1. A 58-year-old male truck driver had a history of progressive angina. Medical therapy was ineffective. Coronary angiography showed an 80% stenosis of the left main trunk and critical stenosis of the circumflex and first diagonal arteries. Myocardial revascularization was performed, with an internal mammary artery graft to the anterior descending coronary artery and a sequential graft of the saphenous vein to the circumflex and first diagonal arteries. His recovery was uneventful, and before discharge he underwent angiography as a part of a protocol to study the effects of antiplatelet drugs on graft patency. The vein graft was patent, but the internal mammary artery showedinterruption of dye flow at the midportion (Fig. 1, A). Despite this finding, the patient had no symptoms, and because of his emotional status, and in agreement with his cardiologist,it was decided not to recommend another operation at that time. Postoperative progress was closely observed, and he resumed work after 2 months. A repeat angiographic study was performed 6 months after the operation. The lesion in the left
From the Cardiac Surgery and Hemodynamic Units, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain. Received for publication Jan. 14, 1986. Accepted for publication Feb. 18, 1986. Address for reprints: Alejandro Aris, M.D., Cardiac Surgery Unit, Hospital de la SantaCreu i Sant Pau,Av. San Antonio M. Claret 167,08025 Barcelona, Spain.
62
main trunk had progressed and the internal mammary artery graft was patent (Fig. I, B). The patient has had no symptoms over the last 20 months despite his heavy work. CASE 2. A 52-year-old man with a history of myocardial infarction underwent cardiac catheterization because of intractable angina. The anterior descending coronary artery was completely occluded at its proximal third, and the circumflex artery had a critical stenosis at its origin. He underwent double coronary artery bypass: an internal mammary artery graft to the left anterior descending artery and a saphenous vein graft to the first marginal branch of the circumflex artery. The anterior descending artery was irregular, with a I mm diameter distal to the anastomosis. Recovery was uneventful, and the patient underwent repeat catheterization before discharge. Both grafts were occluded (Fig. 2, A). The patient refused a second operation, and was discharged taking nifedipine plus topical nitroglycerin. Repeat angiographic study 6 months later (part of the same protocol as in Case 1) showed that the internal mammary artery had regained patency (Fig. 2, B), although progression of the diseasein the grafted artery was evident.The patient is limited by exertional angina, but the extent of his atheromatosis precludes further operation.
Discussion The special characteristics of the internal mammary artery as a conduit for myocardial revascularization have been reported.v ' A decrease in flow may result from the steal phenomenon." spasm, or competitive flow. Dincer and Barner? reported a case similar to ours but with a longer interval. The internal mammary artery was open 1 week after operation, lost its patency at I year, but was open again, in association with progression of proximal coronary disease, at 5 years. They pointed out the possibility of competitive flow as the cause of the temporary closure of the graft. Our case reports support this contention. Close examination of the early postoperative film in Case 1 (Fig. 1, A) showed the end of the dye column to be pulsatile in a fashion that suggested retrograde flow in the internal mammary artery. The
Volume 93 Number 1 January 1987
Patency of internal mammary artery graft
63
Fig. 1. A, Selective angiogram of the left internal mammary artery shows interruption of flow at its rnidportion. B, Six months later the internalmammaryartery has regained patency, filling the leftanterior descending coronary artery (arrow).
anterior descending coronary artery was probably being perfused in part by the other grafts, and mostly through the left main trunk, which showed a significant but not critical lesion. With progression of the disease in the left main trunk, the internal mammary artery regained functional patency (it is safe to assume that it never lost its anatomic patency). In Case 2, the poor distal coronary bed was probably responsible for cessation of flow through the internal mammary artery. Development of collateral circulation or the vasoactive medication could decrease resistance, with reestablishment of flow at a later time. Early patency of the internal mammary artery reflects its ability to remain open in low-flow situa-
tions,!" an advantage not to be found with other kinds of conduits used for coronary bypass. The internal mammary artery is the graft of choice for myocardial revascularization. Care must be exercised to avoid any situation in which competitive flow may occur. Our two cases support the finding of Dincer and Barner" that "occlusion" of an internal mammary artery graft may be reversible. REFERENCES Tector AJ, Schmal TM, Janson B, Kallies JR, JohnsonG: The internal mammary artery graft. Its longevity after coronary bypass. JAMA 246:2181-2183, 1981 2 Grondin CM, Campeau L, Lesperance J, Enjalbert M,
The Journal of
64
Aris, Borras, Ramib
Thoracic and Cardiovascular Surgery
Fig. 2. A, Occlusion of the left internal mammary artery graft. B, Repeat angiogram at 6 months reveals a patent internal mammary artery that fills a diffusely diseased left anterior descending coronary artery (arrows).
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Bourassa MG: Comparison of late changes in internal mammary artery and saphenous vein grafts in two consecutive series of patients 10 years after operation. Circulation 70:Suppl 1:208-212, 1984 Okies JE, Page US, Bigelow JC, Krause AH, Salomon NW: The left internal mammary artery. The graft of choice. Circulation 70:Suppl 1:213-221, 1984 Kay HR, Korns ME, F1emma RJ, Tector AJ, Lepley D Jr: Atherosclerosis of the internal mammary artery. Ann Thorac Surg 21:504-507, 1976 Singh RN, Sosa JA: Internal mammary artery. A "live" conduit for coronary bypass. J THORAC CARDIOVASC SURG 87:936-938, 1984 Singh RN, Sosa JA: Internal mammary artery-coronary artery anastomosis. Influence of the side branches on
7
8
9
10
surgical result. J THORAC CARDIOVASC SURG 82:909-914, 1981 Singh RN, Magovern GJ: Internal mammary graft. Improved flow resulting from correction of steal phenomenon. J THORAC CARDIOVASC SURG 84:146-149, 1982 Pelias AJ, Del Rossi AJ, Tacy L, Wolpowitz A: A case of postoperative internal mammary steal. J THORAC CARDIOVASC SURG 90:794-795, 1985 Dincer B, Barner HB: The "occluded" internal mammary artery graft. Restoration of patency after apparent occlusion associated with progression of coronary disease. J THORAC CARDIOVASC SURG 85:318-320, 1983 Barner HB, Swartz MT, Mudd JG, Tyras DH: Late patency of the internal mammary artery as a coronary conduit. Ann Thorac Surg 34:408-412, 1982