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The Free Internal Mammary Artery Bypass Graft
The Free Internal Mammary Artery Bypass Graft Use of the I M A in the Aorta-to-Coronary Artery Position Floyd D. Loop, M.D., Nick Spampinato, M.D., Chalit Cheanvechai, M.D., and Donald B. EWer, M.D. ABSTRACT Transposition of the internal mammary artery (IMA) into the aorta-to-coronaryartery position is described, and 4 patients who underwent this operation are reported. Currently, this type of bypass graft is reserved for those patients who have unsuitable or stripped saphenous veins. The free IMA grafts can be connected to any of the major coronary vessels, and in most instances optical assistance is not necessary. There was no significant difference in recorded blood flow between these free grafts and a large group of in situ IMAto-coronary artery bypass grafts.
T
he internal mammary artery (IMA) graft is the most recently confirmed method of direct myocardial revascularization. Construction of internal mammary artery-to-coronary artery anastomoses has been greatly facilitated by refinements in microsurgical technique and, in some centers, by the use of high-power optics [l]. Although the technical details differ among surgical groups, the overall results from this revascularization procedure are most encouraging. T h e size of the IMA, which at first seemed to be a major obstacle, has become one of the artery’s most attractive features, because it closely corresponds to the diameter of the major coronary vessels. T h e artery-toartery anastomosis is impressive from a physiological standpoint, especially since obstructive atherosclerosis rarely affects the IMA. During the past year, more than 200 patients have undergone IMA graft procedures at the Cleveland Clinic. Our enthusiasm for the operation continues, and we use it increasingly as a primary procedure. T h e left IMA has been used extensively for grafts to the anterior descending and diagonal branches of the left coronary artery: however, its length and the course of the lateral coronary arteries limit the use of the left IMA to these anterolateral wall vessels. Likewise, the in situ right IMA is confined by length to the upper right coronary artery. Fortunately, these technical problems of distance and position can be overcome by removing the IMA for transposition to the aorta-to-coronary artery position. From the Department o f Thoracic and Cardiovascular Surgery, T h e Cleveland Clinic Foundation and T h e Cleveland Clinic Educational Foundation, Cleveland, Ohio. Accepted for publication May 22, 1972. Address reprint requests t o I)r. Loop, Department of Thoracic and Cardiovascular Surgery, T h e Cleveland Clinic Foundation, 9500 Euclicl Ave., Cleveland, Ohio 44106.
50
THE ANNALS OF THORACIC SURGERY
Free Internal Mammary Artery ByPass Graft
In August, 1971, we encountered a patient who had severe lesions in both anteriw descending and right coronary arteries and in whom the saphenous veins had been surgically removed previously. Faced with the problem that the right IMA would not extend around the margin of the right ventricle, we removed the right IMA and interposed it between the aorta and the distal right coronary artery. The patient’s history, including the postoperative arteriograms, was later reported [2]. Since that time, 3 other patients with right coronary, anterior descending, and circumflex arterial lesions have received IMA bypass grafts in the aorta-to-coronary artery position. Our surgical experience with these free grafts is described, and the results of the early follow-up coronary catheterization studies are included in this report.
Clinical Material and Case Reports Four patients have received aorta-to-coronary artery IMA grafts in the six months ending February 1, 1972. The distal anastomoses were centered, respectively, on the right coronary artery in 2 patients, the anterior descending coronary artery in the third patient, and the posterolateral branch of the circumflex coronary artery in the fourth patient. This type of procedure was indicated primarily because of extensive varicosities or because previously the saphenous veins had been removed bilaterally. Patient 1. A 57-year-old man who had a history of myocardial infarction one year previously was admitted for evaluation. He experienced angina pectoris with even mild exertion (New York Heart Association Functional Class III-IV) . The physical examination was unremarkable except for bilateral large varicosities in both lower extremities. The electrocardiogram recorded evidence of a remote anterior wall infarct. Cine coronary arteriography showed 90% proximal narrowing in a dominant right coronary artery, subtotal occlusion of the anterior descending coronary artery distal to the origin of the first septa1 perforator, and mild disease in the circumflex distribution. The anterolateral wall of the left ventricle was moderately impaired, and the left ventricular end-diastolic pressure was 15 mm. Hg. At operation, both internal mammary arteries were mobilized from the chest wall, and the left IMA was grafted to the middle segment of the anterior descending coronary artery. The right IMA was removed and used as a free aorta-to-coronary artery graft to the bifurcation of the right coronary artery. Coronary arteriography was repeated on the tenth postoperative day, and both grafts were widely patent. Now, six months postoperatively, the patient is without pain and has returned to work. Patient 2. A 47-year-old man had been briefly hospitalized one year previously for coronary insufficiency and on admission had atypical angina VOL.
15,
NO.
1,
JANUARY,
1973
51
LOOP E T AL.
pectoris. Physical examination showed large varicosities in both lower extremities. The electrocardiogram was interpreted as normal. Cine coronary arteriography demonstrated total occlusion of a small left anterior descending coronary artery above the first septa1 perforator. T h e other two major coronary arteries and the ventriculogram were interpreted as normal. Considering that the patient had varicose veins bilaterally and a relatively small coronary artery, we decided to perform a left IMA graft to the anterior descending coronary artery. T h e left IMA was inadvertently injured during mobilization and was therefore not suitable for use as a direct graft. T h e right IMA was then detached and removed for use as an aorta-toanterior descending coronary artery bypass graft. T h e postoperative course was uncomplicated, and he was discharged on the ninth postoperative day. A second arteriogram performed two months after operation showed a patent IMA graft that perfused the anterior descending coronary artery and its diagonal branches (Fig. 1 ) . Now, four months postoperatively, the patient is completely asymptomatic and working full time. Patient 3 . A 57-year-old man underwent cine coronary arteriography after complaints of increasingly severe angina pectoris (Functional Class III-IV) . T h e arteriogram showed complete occlusion of the proximal right coronary artery with an adequate runoff. The ventriculogram demonstrated good contraction in all segments of the left ventricle. A.t operation in January, 1972, the saphenous veins were considered too large for grafting to the right coronary artery. As an alternate procedure, an aorta-to-coronary artery graft was performed using a transposed right IMA as a free graft from the aorta. T h e patient had an uncomplicated postoperative
A
B
FIG. i'. Patient 1 . ( A ) Right anterior oblique projection showing total occlusion of the anterior descending coronary artery (arrow), which is filled by collaterals from the right coronary artery. ( B ) A patent aorta-to-anteribr descending ZMA graft in the left anterior oblique view. T h e second arteriogram was performed two months after operation.
52
THE ANNALS OF THORACIC SURGERY
Free Internal Mammary Artery Bypass Graft
A
B
FIG. 2. Patient 4 . ( A ) Coronary arteriography demonstrates subtotal occlusion in both anterior descending and lateral Circumflex branches of the left coronary artery. ( B ) Postoperative arteriogram shows a free ZMA gmft from,the aorta to the obstructed circumfEex coronary artery. A n in situ left ZMA graft (not shown) centered on the anterior descending coronary artery was also widely patent.
course and was discharged after repeat coronary arteriograms showed a widely patent IMA-to-right coronary artery graft. Patient 4. Coronary arteriography was performed on a 56-year-old man who had a short history of mild angina pectoris (Functional Class 11) . There were no myocardial infarctions in the history, and his electrocardiogram was interpreted as normal. T h e cine coronary arteriographic study revealed an 80% obstruction in the proximal anterior descending coronary artery and a 90% occlusion in the posterolateral branch of the circumflex artery. Moderate impairment of the diaphragmatic wall was noted on left ventr iculograph y. T h e patient had previously undergone bilateral ligation and stripping of the saphenous veins. T h e surgical procedure consisted of a free right IMA graft to the circumflex coronary artery, while the left IMA was directly anastomosed to the middle one-third of the anterior descending coronary artery. He had an uneventful hospital convalescence, and a second catheterization study demonstrated patency of both grafts (Fig. 2) .
Comment T h e free IMA graft is an alternate method of coronary revascularization for patients who have absent or otherwise unsuitable saphenous veins. T h e diameter of the IMA is relatively large, between 2 and 3 mm. down to its sixth intercostal branch. Thereafter, the artery becomes smaller and, accordingly, the blood flow is reduced. T h e larger segment of the left IMA easily reaches the anterior descending and diagonal coronary arteries, but angulation over the pericardial brim and the posterior location of the major circumflex branches virtually restrict a wider application of the left in situ VOL.
15,
NO.
1,
JANUARY,
1973
53
LOOP E T AL.
graft. T h e peripheral distribution of atherosclerotic disease in the right coronary artery often requires that the bypass graft be placed near or on the bifurcation and sometimes farther out onto the posterior descending or the atrioventricular arteries-far too distal for an in situ right IMA graft. T h e IMA transposed to the aorta-to-coronary artery position represents an ideal conduit in size and will reach any of the major coronary arterial branches. Since the superior portion of the IMA measures 3 mm. or more in diameter, the proximal anastomosis is completed first to utilize the vessel at its greatest width. A small triangle is excised from the aorta, and the proximal anastomosis is constructed with interrupted 7-0 silk sutures. T h e pedicle is then measured to the anastomotic site on the involved coronary artery. All these procedures are completed before cardiopulmonary bypass is begun. When a coronary artery receiving an IMA graft is more than 1 mm. in diameter, high-power magnification is not required. Such was the case in these 4 patients, and no optical aids were used to connect any of the free IMA grafts. Both anastomoses were performed using an interrupted 7-0 silk suture technique. It has been suggested that the higher prolonged diastolic flow in grafts originating from the ascending aorta provides a greater coronary filling than the in situ left IMA grafts [3]. This observation is probably more of a theoretical than a practical advantage, since the main determinants of graft flow are the demand or perfusion deficit and the adequacy of coronary arterial runoff. The IMA flow measurements in the operating room depend directly on the above factors and also on the amount of arterial spasm present under the conditions of the recording. If no vasodilator is applied to the IMA, mean flow for a typical left IMA-to-anterior descending coronary artery graft is approximately 20 ml. per minute. This flow can be doubled and even tripled if the pedicle is sprayed with a 3 : l papaverine solution or wrapped in moist gauze containing the diluted amount of papaverine. FIG. ?. Comparison of flow patterns of in situ ( A ) and aorta-to-coronary artery ( B ) ZMA grafts. T h e diastolic filling periods are essentially equal. Differences in mean flow are mainly a result of arterial spasm in the grafts. T h e free ZMA graft was not treated with topical papaverine.
54
T H E ANNALS OF THORACIC SURGERY
Free Internal Mammary Artery Bypass Graft
After completion of both in situ and free IMA grafts, we find no striking difference in the mean flow rates, and the diastolic filling times differ by only a few milliseconds (Fig. 3) . T h e IMA is capable of delivering a flow of well over 100 ml. per minute, and these lower flows constitute an isolated recording in the operating room, frequently under unstable conditions. The velocity of contrast material often seen in the postoperative arteriogram suggests that much higher flows can be obtained, but as yet there is no reliable method to determine late postoperative flow during the follow-up cardiac catheterization study.
References 1. Green, G. E., Stertzer, S. H., Gordon, R. B., and Tice, D. A. Anastomosis of the internal mammary artery to the distal left anterior descending coronary artery. Circulation 41 (Suppl. II):79, 1970. 2. Loop, F. D., Effler, D. B., Spampinato, N., Groves, L. K., and Cheanvechai, C. Myocardial revascularization by internal mammary artery graft: A technique without optical assistance. ]. Thorac. Cardiovasc. Surg. 63:674, 1972. 3. Wakabayashi, A., Beron, E., Lou, M. A., Mino, J. Y.,da Costa, I. A., and Connolly, J. E. Physiological basis for the systemic-to-coronaryartery bypass graft. Arch. Surg. 100:17, 1970.
VOL.
15,
NO.
1, JANUARY,
1973
55
T
he internal mammary artery (IMA) graft is the most recently confirmed method of direct myocardial revascularization. Construction of internal mammary artery-to-coronary artery anastomoses has been greatly facilitated by refinements in microsurgical technique and, in some centers, by the use of high-power optics [l]. Although the technical details differ among surgical groups, the overall results from this revascularization procedure are most encouraging. T h e size of the IMA, which at first seemed to be a major obstacle, has become one of the artery’s most attractive features, because it closely corresponds to the diameter of the major coronary vessels. T h e artery-toartery anastomosis is impressive from a physiological standpoint, especially since obstructive atherosclerosis rarely affects the IMA. During the past year, more than 200 patients have undergone IMA graft procedures at the Cleveland Clinic. Our enthusiasm for the operation continues, and we use it increasingly as a primary procedure. T h e left IMA has been used extensively for grafts to the anterior descending and diagonal branches of the left coronary artery: however, its length and the course of the lateral coronary arteries limit the use of the left IMA to these anterolateral wall vessels. Likewise, the in situ right IMA is confined by length to the upper right coronary artery. Fortunately, these technical problems of distance and position can be overcome by removing the IMA for transposition to the aorta-to-coronary artery position. From the Department o f Thoracic and Cardiovascular Surgery, T h e Cleveland Clinic Foundation and T h e Cleveland Clinic Educational Foundation, Cleveland, Ohio. Accepted for publication May 22, 1972. Address reprint requests t o I)r. Loop, Department of Thoracic and Cardiovascular Surgery, T h e Cleveland Clinic Foundation, 9500 Euclicl Ave., Cleveland, Ohio 44106.
50
THE ANNALS OF THORACIC SURGERY
Free Internal Mammary Artery ByPass Graft
In August, 1971, we encountered a patient who had severe lesions in both anteriw descending and right coronary arteries and in whom the saphenous veins had been surgically removed previously. Faced with the problem that the right IMA would not extend around the margin of the right ventricle, we removed the right IMA and interposed it between the aorta and the distal right coronary artery. The patient’s history, including the postoperative arteriograms, was later reported [2]. Since that time, 3 other patients with right coronary, anterior descending, and circumflex arterial lesions have received IMA bypass grafts in the aorta-to-coronary artery position. Our surgical experience with these free grafts is described, and the results of the early follow-up coronary catheterization studies are included in this report.
Clinical Material and Case Reports Four patients have received aorta-to-coronary artery IMA grafts in the six months ending February 1, 1972. The distal anastomoses were centered, respectively, on the right coronary artery in 2 patients, the anterior descending coronary artery in the third patient, and the posterolateral branch of the circumflex coronary artery in the fourth patient. This type of procedure was indicated primarily because of extensive varicosities or because previously the saphenous veins had been removed bilaterally. Patient 1. A 57-year-old man who had a history of myocardial infarction one year previously was admitted for evaluation. He experienced angina pectoris with even mild exertion (New York Heart Association Functional Class III-IV) . The physical examination was unremarkable except for bilateral large varicosities in both lower extremities. The electrocardiogram recorded evidence of a remote anterior wall infarct. Cine coronary arteriography showed 90% proximal narrowing in a dominant right coronary artery, subtotal occlusion of the anterior descending coronary artery distal to the origin of the first septa1 perforator, and mild disease in the circumflex distribution. The anterolateral wall of the left ventricle was moderately impaired, and the left ventricular end-diastolic pressure was 15 mm. Hg. At operation, both internal mammary arteries were mobilized from the chest wall, and the left IMA was grafted to the middle segment of the anterior descending coronary artery. The right IMA was removed and used as a free aorta-to-coronary artery graft to the bifurcation of the right coronary artery. Coronary arteriography was repeated on the tenth postoperative day, and both grafts were widely patent. Now, six months postoperatively, the patient is without pain and has returned to work. Patient 2. A 47-year-old man had been briefly hospitalized one year previously for coronary insufficiency and on admission had atypical angina VOL.
15,
NO.
1,
JANUARY,
1973
51
LOOP E T AL.
pectoris. Physical examination showed large varicosities in both lower extremities. The electrocardiogram was interpreted as normal. Cine coronary arteriography demonstrated total occlusion of a small left anterior descending coronary artery above the first septa1 perforator. T h e other two major coronary arteries and the ventriculogram were interpreted as normal. Considering that the patient had varicose veins bilaterally and a relatively small coronary artery, we decided to perform a left IMA graft to the anterior descending coronary artery. T h e left IMA was inadvertently injured during mobilization and was therefore not suitable for use as a direct graft. T h e right IMA was then detached and removed for use as an aorta-toanterior descending coronary artery bypass graft. T h e postoperative course was uncomplicated, and he was discharged on the ninth postoperative day. A second arteriogram performed two months after operation showed a patent IMA graft that perfused the anterior descending coronary artery and its diagonal branches (Fig. 1 ) . Now, four months postoperatively, the patient is completely asymptomatic and working full time. Patient 3 . A 57-year-old man underwent cine coronary arteriography after complaints of increasingly severe angina pectoris (Functional Class III-IV) . T h e arteriogram showed complete occlusion of the proximal right coronary artery with an adequate runoff. The ventriculogram demonstrated good contraction in all segments of the left ventricle. A.t operation in January, 1972, the saphenous veins were considered too large for grafting to the right coronary artery. As an alternate procedure, an aorta-to-coronary artery graft was performed using a transposed right IMA as a free graft from the aorta. T h e patient had an uncomplicated postoperative
A
B
FIG. i'. Patient 1 . ( A ) Right anterior oblique projection showing total occlusion of the anterior descending coronary artery (arrow), which is filled by collaterals from the right coronary artery. ( B ) A patent aorta-to-anteribr descending ZMA graft in the left anterior oblique view. T h e second arteriogram was performed two months after operation.
52
THE ANNALS OF THORACIC SURGERY
Free Internal Mammary Artery Bypass Graft
A
B
FIG. 2. Patient 4 . ( A ) Coronary arteriography demonstrates subtotal occlusion in both anterior descending and lateral Circumflex branches of the left coronary artery. ( B ) Postoperative arteriogram shows a free ZMA gmft from,the aorta to the obstructed circumfEex coronary artery. A n in situ left ZMA graft (not shown) centered on the anterior descending coronary artery was also widely patent.
course and was discharged after repeat coronary arteriograms showed a widely patent IMA-to-right coronary artery graft. Patient 4. Coronary arteriography was performed on a 56-year-old man who had a short history of mild angina pectoris (Functional Class 11) . There were no myocardial infarctions in the history, and his electrocardiogram was interpreted as normal. T h e cine coronary arteriographic study revealed an 80% obstruction in the proximal anterior descending coronary artery and a 90% occlusion in the posterolateral branch of the circumflex artery. Moderate impairment of the diaphragmatic wall was noted on left ventr iculograph y. T h e patient had previously undergone bilateral ligation and stripping of the saphenous veins. T h e surgical procedure consisted of a free right IMA graft to the circumflex coronary artery, while the left IMA was directly anastomosed to the middle one-third of the anterior descending coronary artery. He had an uneventful hospital convalescence, and a second catheterization study demonstrated patency of both grafts (Fig. 2) .
Comment T h e free IMA graft is an alternate method of coronary revascularization for patients who have absent or otherwise unsuitable saphenous veins. T h e diameter of the IMA is relatively large, between 2 and 3 mm. down to its sixth intercostal branch. Thereafter, the artery becomes smaller and, accordingly, the blood flow is reduced. T h e larger segment of the left IMA easily reaches the anterior descending and diagonal coronary arteries, but angulation over the pericardial brim and the posterior location of the major circumflex branches virtually restrict a wider application of the left in situ VOL.
15,
NO.
1,
JANUARY,
1973
53
LOOP E T AL.
graft. T h e peripheral distribution of atherosclerotic disease in the right coronary artery often requires that the bypass graft be placed near or on the bifurcation and sometimes farther out onto the posterior descending or the atrioventricular arteries-far too distal for an in situ right IMA graft. T h e IMA transposed to the aorta-to-coronary artery position represents an ideal conduit in size and will reach any of the major coronary arterial branches. Since the superior portion of the IMA measures 3 mm. or more in diameter, the proximal anastomosis is completed first to utilize the vessel at its greatest width. A small triangle is excised from the aorta, and the proximal anastomosis is constructed with interrupted 7-0 silk sutures. T h e pedicle is then measured to the anastomotic site on the involved coronary artery. All these procedures are completed before cardiopulmonary bypass is begun. When a coronary artery receiving an IMA graft is more than 1 mm. in diameter, high-power magnification is not required. Such was the case in these 4 patients, and no optical aids were used to connect any of the free IMA grafts. Both anastomoses were performed using an interrupted 7-0 silk suture technique. It has been suggested that the higher prolonged diastolic flow in grafts originating from the ascending aorta provides a greater coronary filling than the in situ left IMA grafts [3]. This observation is probably more of a theoretical than a practical advantage, since the main determinants of graft flow are the demand or perfusion deficit and the adequacy of coronary arterial runoff. The IMA flow measurements in the operating room depend directly on the above factors and also on the amount of arterial spasm present under the conditions of the recording. If no vasodilator is applied to the IMA, mean flow for a typical left IMA-to-anterior descending coronary artery graft is approximately 20 ml. per minute. This flow can be doubled and even tripled if the pedicle is sprayed with a 3 : l papaverine solution or wrapped in moist gauze containing the diluted amount of papaverine. FIG. ?. Comparison of flow patterns of in situ ( A ) and aorta-to-coronary artery ( B ) ZMA grafts. T h e diastolic filling periods are essentially equal. Differences in mean flow are mainly a result of arterial spasm in the grafts. T h e free ZMA graft was not treated with topical papaverine.
54
T H E ANNALS OF THORACIC SURGERY
Free Internal Mammary Artery Bypass Graft
After completion of both in situ and free IMA grafts, we find no striking difference in the mean flow rates, and the diastolic filling times differ by only a few milliseconds (Fig. 3) . T h e IMA is capable of delivering a flow of well over 100 ml. per minute, and these lower flows constitute an isolated recording in the operating room, frequently under unstable conditions. The velocity of contrast material often seen in the postoperative arteriogram suggests that much higher flows can be obtained, but as yet there is no reliable method to determine late postoperative flow during the follow-up cardiac catheterization study.
References 1. Green, G. E., Stertzer, S. H., Gordon, R. B., and Tice, D. A. Anastomosis of the internal mammary artery to the distal left anterior descending coronary artery. Circulation 41 (Suppl. II):79, 1970. 2. Loop, F. D., Effler, D. B., Spampinato, N., Groves, L. K., and Cheanvechai, C. Myocardial revascularization by internal mammary artery graft: A technique without optical assistance. ]. Thorac. Cardiovasc. Surg. 63:674, 1972. 3. Wakabayashi, A., Beron, E., Lou, M. A., Mino, J. Y.,da Costa, I. A., and Connolly, J. E. Physiological basis for the systemic-to-coronaryartery bypass graft. Arch. Surg. 100:17, 1970.
VOL.
15,
NO.
1, JANUARY,
1973
55