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Myocardial revascularization with the “horseshoe” graft
Myocardial revascularization with the "horseshoe" graft Postoperative evaluation Laurence K. Groves, M.D.,* William C. Sheldon, M.D.,** and Gary M. Silver, M.D., *** Cleveland, Ohio
The vein graft era of direct myocardial revascularization is now more than five years old. As increasing numbers of bypass grafts were performed, the senior author (L. K. G.) began using what we have called the "horseshoe" vein graft-a looped segment of vein with each end anastomosed to a coronary artery and the midportion anastomosed crosswise, side-to-side to the ascending aorta (Fig. 1). The obvious virtue of this technique is that, with three anastomoses instead of four, a vein graft can be run from the ascending aorta to two separate coronary arteries. The time thus saved was the justification for using the procedure. Also, one aortic anastomosis may be desirable if the aorta is diseased or if exposure is difficult (short ascending aorta). There were no obvious technical drawbacks to the technique as it evolved, and between Sept. 19, 1969, and Sept. 18, 1972, it was used on 294 separate patients. Angiographic evaluation of this experience suggests that From the Cleveland Clinic, Cleveland, Ohio 44106. Received for publication May 29, 1973. Address for reprints: Laurence K. Groves, M.D., Cleveland Clinic, 9500 Euclid Ave., Cleveland, Ohio 44106. 'Staff, Department of Thoracic and Cardiovascular Surgery. "Staff, Department of Cardiovascular Disease and the Cardiac Laboratory. ••• Senior Fellow, Department of Thoracic and Cardiovascular Surgery.
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there is very little difference in patency of horseshoe limbs when compared to double grafts with separate aortic anastomoses. Technical considerations It is self-evident that flow through one limb of a horseshoe graft will be opposed by any valves which may be present. For this reason, the competence of these valves was destroyed with blunt-tipped, alligator-type Stevenson neurosurgical scissors (Fig. 2). The use of this instrument seemed atraumatic, and successful destruction of valve competence was always verified by running a stream of isotonic saline down the vein against the valves. Data presented below indicate that neither limb of such grafts had a greater predilection to occlusion. During the stated time interval, this technique was used routinely by L. K. G. in cases in which a graft was performed to both the right and the left coronary arterial trees. In many instances, in addition to the horseshoe graft, a third, fourth, and in one instance a fifth coronary artery was grafted either from one of the horseshoe limbs or from another aortic anastomosis. The horsehoe technique was never used for two left coronary branches, i.e., grafts to the circumflex and anterior descending coronary arteries. The acuteness of the angle at the aortic anas-
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Myocardial revascularization
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Fig. 2. These alligator-type scissors prove very suitable for rendering valves incompetent. As the valves are divided, the vein can be easily piled up accord ion-fashion on the shaft of the scissors.
supplemental endarterectomy was used in 31 (27.7 per cent) of the RCA's, four LAD 's, and one diagonal vessel. Results
Fig. 1. This drawing depicts a typical "horseshoe" vein graft , in this case to the anterior descending and right coronary arteries. First, the competence of the valves must be destroyed. Orientation of the limbs varies from case to case, most commonly depending on the size of the coronary arteries in relat ion to the size of the two ends of the vein graft.
tomosis (the midportion of the horseshoe) precludes the use of this technique under these circumstances. All anastomoses were performed with interrupted 6-0 silk suture technique. Clinical material
As of March 1, 1973, 112 patients had been restudied angiographically from 1 to 28 months after operation. The following data refer only to the two arteries to which the horseshoe graft was primarily anastomosed. The 224 vessels grafted were divided as follows: 112 right coronary arteries (RCA); 84 left anterior descending coronary arteries (LAD); 26 circumflex coronary arteries; and two diagonal branches of the LAD. A
The operative procedure did not prove to be intrinsically hazardous. Of the 294 patients so treated, 2 died in the hospital, for a hospital mortality rate of 0.7 per cent. At recatheterization, 62 of the 224 graft limbs (30 RCA 's, 23 LAD's, and nine circumflex) were occluded (72.3 per cent patency). In 11 patients (10 per cent), both limbs had closed: 7 LAD and RCA grafts, 4 circumflex and RCA grafts. In 18 of the remaining patients with a single limb closed, the occluded limbs carried flow against the valves, whereas in 18 others the limb carried flow with the valves. In 4 cases, it could not be determined from the operative description which limb contained the valves oriented against the direction of the flow. An endarterectomy of the RCA enhanced the patency rate in this series. Of the 31 RCA's subjected to endarterectomy, 27 (87.1 per cent) were patent at restudy, as was the one diagonal branch that required endarterectomy. However, only one of the four LAD's subjected to endarterectomy was patent. These data are summarized in Tables I and II. The patency of horseshoe grafts (72.3 per cent of 224 graft limbs) was compared
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Groves, Sheldon, Silver
Thoracic and Cardiovascular Surgery
Table t. Recatheterization data on 112 horseshoe grafts Vessel
I
I
I
No. Per cent Per cent grafted Occluded patent occluded
RCA LAD Circumflex Diagonal
112 84
30 23
26 2
0
Total
224
62
9
73.2 73 64 100 72.3
26.8 27 36 27.7
Legend: RCA, Right coronary artery. LAD, Left anterior descending coronary artery.
Table II. Horseshoe plus endarterectomy: Postoperative assessment of individual limbs Vessel
Total
RCA LAD Diagonal
31 4 1
Per cent occluded
4 3 0
87.1 25 100
12.9 75
For legend, see Table J.
to graft patency in other patients who had had vein grafts to two coronary artery branches but in whom separate aortic ostia were used for each limb. A total of 474 such separate double grafts were studied at varying postoperative intervals (237 patients). Of these graft limbs, 104 were occluded (21.9 per cent); 78.1 per cent were patent. Among the patients studied, therefore, the patency rate for the individual limbs:zs; is 6 per cent lower with the horseshoe techm ue. The significance 0 t IS rat er small difference is difficult to assess. Blood flow against the valves which were rendered incompetent at surgery does not appear to be a major factor, but the related intraluminal instrumentation could be significant. Selection of patients for horseshoe grafts plus other technical factors may contribute to the slightly lower patency. Among the surgeons doing this type of surgery at the Cleveland Clinic, L. K. G. has expressed most interest in endarterectomy, and it is fair to say that some patients thought in advance to be probable candidates for endarterectomy were referred to him. However, the previously cited figures indicate
that the patency rate was higher in patients who had a right endarterectomy associated with the horseshoe graft than was the rate in the horseshoe graft group as a whole or the group with double grafts and separate aortic ostia. There are definite angiographic criteria for suitability of coronary arteries for vein graft surgery. If a patient is to have a single coronary artery graft with the saphenous vein, he will usually fulfill these criteria quite closely. In many instances, however, as a secondary objective one or more additional grafts may be performed to other coronary branches which, for one reason or another, are less than ideal. This extension of the surgical indications has proved to be of low risk and very worthwhile in many patients; however, not surprisingly, it does result in a slightly lower patency rate in postoperative angiographic studies. In the Cleveland Clinic experience, 80.6 per cent (614 of 762 grafts) of single vein grafts studied at varying postoperative intervals were patent. In contrast, 76.6 per cent (625 of 816 grafts) of the graft limbs in patients who had had multiple vein grafts were patent. This consideration should have no more unfavorable effect on the horseshoe vein grafts than on other multiple vein grafts. Discussion
On the basis of the data reported above, it is apparent that in our experience patency rates are better among patients selected for single grafts than for multiple grafts. The horseshoe technique for double grafts is associated with a slightly lower patency rate than when separate aortic ostia are used. An associated endarterectomy appears to improve the results and may permit direct graft reconstruction of an artery that otherwise would be unsuitable. The horseshoe technique can be useful in certain instances, such as in patients with degenerative aortitis, in those who have a short ascending aorta and require multiple grafts, or in those whose condition dictates a brief surgical procedure.
Volume 66 Number 4
Myocardial revascularization
625
October, 1973
Myocardial revascularization with saphenous vein graft techniques can be a complicated, tedious surgical exercise, and exploration of surgical shortcuts is certainly justified. In another technical modification, a single graft is constructed end-to-side from the ascending aorta with two distal anastomoses to coronary arteries, one side-to-side and the other end-to-side; we call this a "bridge graft." These grafts have not yet been restudied angiographically in sufficient numbers to permit an assessment of results. Bartley' reported a similar technique for multiple coronary artery branches, arguing that the increased flow will increase patency rates. All of these surgical shortcuts have the theoretical drawback of allow-
ing one anastomotic failure to occlude multiple grafts. Current information suggests that separate grafts to separate arteries are probably preferable in most patients and offer the optimal likelihood of long-term graft patency. Various modifications, including the horseshoe technique described here, may be useful in certain individuals with special surgical problems, abnormal anatomy, or diseased aortas. These techniques warrant careful, continued assessment. REFERENCE Bartley, T. D., Bigelow, 1. c., and Page, U. S.: Aortocoronary Bypass Grafting With Multiple Sequential Anastomoses to a Single Vein, Arch. Surg. 105: 915, 1972.
The vein graft era of direct myocardial revascularization is now more than five years old. As increasing numbers of bypass grafts were performed, the senior author (L. K. G.) began using what we have called the "horseshoe" vein graft-a looped segment of vein with each end anastomosed to a coronary artery and the midportion anastomosed crosswise, side-to-side to the ascending aorta (Fig. 1). The obvious virtue of this technique is that, with three anastomoses instead of four, a vein graft can be run from the ascending aorta to two separate coronary arteries. The time thus saved was the justification for using the procedure. Also, one aortic anastomosis may be desirable if the aorta is diseased or if exposure is difficult (short ascending aorta). There were no obvious technical drawbacks to the technique as it evolved, and between Sept. 19, 1969, and Sept. 18, 1972, it was used on 294 separate patients. Angiographic evaluation of this experience suggests that From the Cleveland Clinic, Cleveland, Ohio 44106. Received for publication May 29, 1973. Address for reprints: Laurence K. Groves, M.D., Cleveland Clinic, 9500 Euclid Ave., Cleveland, Ohio 44106. 'Staff, Department of Thoracic and Cardiovascular Surgery. "Staff, Department of Cardiovascular Disease and the Cardiac Laboratory. ••• Senior Fellow, Department of Thoracic and Cardiovascular Surgery.
622
there is very little difference in patency of horseshoe limbs when compared to double grafts with separate aortic anastomoses. Technical considerations It is self-evident that flow through one limb of a horseshoe graft will be opposed by any valves which may be present. For this reason, the competence of these valves was destroyed with blunt-tipped, alligator-type Stevenson neurosurgical scissors (Fig. 2). The use of this instrument seemed atraumatic, and successful destruction of valve competence was always verified by running a stream of isotonic saline down the vein against the valves. Data presented below indicate that neither limb of such grafts had a greater predilection to occlusion. During the stated time interval, this technique was used routinely by L. K. G. in cases in which a graft was performed to both the right and the left coronary arterial trees. In many instances, in addition to the horseshoe graft, a third, fourth, and in one instance a fifth coronary artery was grafted either from one of the horseshoe limbs or from another aortic anastomosis. The horsehoe technique was never used for two left coronary branches, i.e., grafts to the circumflex and anterior descending coronary arteries. The acuteness of the angle at the aortic anas-
Volume 66 Number 4 October, 1973
Myocardial revascularization
623
Fig. 2. These alligator-type scissors prove very suitable for rendering valves incompetent. As the valves are divided, the vein can be easily piled up accord ion-fashion on the shaft of the scissors.
supplemental endarterectomy was used in 31 (27.7 per cent) of the RCA's, four LAD 's, and one diagonal vessel. Results
Fig. 1. This drawing depicts a typical "horseshoe" vein graft , in this case to the anterior descending and right coronary arteries. First, the competence of the valves must be destroyed. Orientation of the limbs varies from case to case, most commonly depending on the size of the coronary arteries in relat ion to the size of the two ends of the vein graft.
tomosis (the midportion of the horseshoe) precludes the use of this technique under these circumstances. All anastomoses were performed with interrupted 6-0 silk suture technique. Clinical material
As of March 1, 1973, 112 patients had been restudied angiographically from 1 to 28 months after operation. The following data refer only to the two arteries to which the horseshoe graft was primarily anastomosed. The 224 vessels grafted were divided as follows: 112 right coronary arteries (RCA); 84 left anterior descending coronary arteries (LAD); 26 circumflex coronary arteries; and two diagonal branches of the LAD. A
The operative procedure did not prove to be intrinsically hazardous. Of the 294 patients so treated, 2 died in the hospital, for a hospital mortality rate of 0.7 per cent. At recatheterization, 62 of the 224 graft limbs (30 RCA 's, 23 LAD's, and nine circumflex) were occluded (72.3 per cent patency). In 11 patients (10 per cent), both limbs had closed: 7 LAD and RCA grafts, 4 circumflex and RCA grafts. In 18 of the remaining patients with a single limb closed, the occluded limbs carried flow against the valves, whereas in 18 others the limb carried flow with the valves. In 4 cases, it could not be determined from the operative description which limb contained the valves oriented against the direction of the flow. An endarterectomy of the RCA enhanced the patency rate in this series. Of the 31 RCA's subjected to endarterectomy, 27 (87.1 per cent) were patent at restudy, as was the one diagonal branch that required endarterectomy. However, only one of the four LAD's subjected to endarterectomy was patent. These data are summarized in Tables I and II. The patency of horseshoe grafts (72.3 per cent of 224 graft limbs) was compared
The Journol of
624
Groves, Sheldon, Silver
Thoracic and Cardiovascular Surgery
Table t. Recatheterization data on 112 horseshoe grafts Vessel
I
I
I
No. Per cent Per cent grafted Occluded patent occluded
RCA LAD Circumflex Diagonal
112 84
30 23
26 2
0
Total
224
62
9
73.2 73 64 100 72.3
26.8 27 36 27.7
Legend: RCA, Right coronary artery. LAD, Left anterior descending coronary artery.
Table II. Horseshoe plus endarterectomy: Postoperative assessment of individual limbs Vessel
Total
RCA LAD Diagonal
31 4 1
Per cent occluded
4 3 0
87.1 25 100
12.9 75
For legend, see Table J.
to graft patency in other patients who had had vein grafts to two coronary artery branches but in whom separate aortic ostia were used for each limb. A total of 474 such separate double grafts were studied at varying postoperative intervals (237 patients). Of these graft limbs, 104 were occluded (21.9 per cent); 78.1 per cent were patent. Among the patients studied, therefore, the patency rate for the individual limbs:zs; is 6 per cent lower with the horseshoe techm ue. The significance 0 t IS rat er small difference is difficult to assess. Blood flow against the valves which were rendered incompetent at surgery does not appear to be a major factor, but the related intraluminal instrumentation could be significant. Selection of patients for horseshoe grafts plus other technical factors may contribute to the slightly lower patency. Among the surgeons doing this type of surgery at the Cleveland Clinic, L. K. G. has expressed most interest in endarterectomy, and it is fair to say that some patients thought in advance to be probable candidates for endarterectomy were referred to him. However, the previously cited figures indicate
that the patency rate was higher in patients who had a right endarterectomy associated with the horseshoe graft than was the rate in the horseshoe graft group as a whole or the group with double grafts and separate aortic ostia. There are definite angiographic criteria for suitability of coronary arteries for vein graft surgery. If a patient is to have a single coronary artery graft with the saphenous vein, he will usually fulfill these criteria quite closely. In many instances, however, as a secondary objective one or more additional grafts may be performed to other coronary branches which, for one reason or another, are less than ideal. This extension of the surgical indications has proved to be of low risk and very worthwhile in many patients; however, not surprisingly, it does result in a slightly lower patency rate in postoperative angiographic studies. In the Cleveland Clinic experience, 80.6 per cent (614 of 762 grafts) of single vein grafts studied at varying postoperative intervals were patent. In contrast, 76.6 per cent (625 of 816 grafts) of the graft limbs in patients who had had multiple vein grafts were patent. This consideration should have no more unfavorable effect on the horseshoe vein grafts than on other multiple vein grafts. Discussion
On the basis of the data reported above, it is apparent that in our experience patency rates are better among patients selected for single grafts than for multiple grafts. The horseshoe technique for double grafts is associated with a slightly lower patency rate than when separate aortic ostia are used. An associated endarterectomy appears to improve the results and may permit direct graft reconstruction of an artery that otherwise would be unsuitable. The horseshoe technique can be useful in certain instances, such as in patients with degenerative aortitis, in those who have a short ascending aorta and require multiple grafts, or in those whose condition dictates a brief surgical procedure.
Volume 66 Number 4
Myocardial revascularization
625
October, 1973
Myocardial revascularization with saphenous vein graft techniques can be a complicated, tedious surgical exercise, and exploration of surgical shortcuts is certainly justified. In another technical modification, a single graft is constructed end-to-side from the ascending aorta with two distal anastomoses to coronary arteries, one side-to-side and the other end-to-side; we call this a "bridge graft." These grafts have not yet been restudied angiographically in sufficient numbers to permit an assessment of results. Bartley' reported a similar technique for multiple coronary artery branches, arguing that the increased flow will increase patency rates. All of these surgical shortcuts have the theoretical drawback of allow-
ing one anastomotic failure to occlude multiple grafts. Current information suggests that separate grafts to separate arteries are probably preferable in most patients and offer the optimal likelihood of long-term graft patency. Various modifications, including the horseshoe technique described here, may be useful in certain individuals with special surgical problems, abnormal anatomy, or diseased aortas. These techniques warrant careful, continued assessment. REFERENCE Bartley, T. D., Bigelow, 1. c., and Page, U. S.: Aortocoronary Bypass Grafting With Multiple Sequential Anastomoses to a Single Vein, Arch. Surg. 105: 915, 1972.