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Bridge saphenous vein graft
Bridge saphenous vein graft Single aorta-coronary artery vein grafts (bridge grafts} were constructed to two coronary branches with a side-to-side anastomosis and an end-to-side anastomosis in 250 patients. Most of these grafts were constructed between circumflex branches (96 grafts), circumflex and diagonal branches (47 grafts), and anterior descending and diagonal branches (79 grafts). The aim of the bridge graft is to decrease the number of anastomoses, decrease the operative time, and improve graft patency. The hospital mortality rate in this group of patients was 1.2 per cent, and the incidence of postoperative myocardial infarction was 3.6 per cent. One hundred ten patients were restudied after surgery; the average time of restudy was 1 year. Ninety-two grafts or 83.6 per cent had two anastomosis patent; 6 grafts (5.4 per cent) had one anastomosis patent; and in 12 grafts (10.9 per cent), both anastomoses were occluded. One hundred twenty-six associated grafts were studied at the same time; the patency rate was 84.1 per cent. From this experience, we believe the bridge graft is a useful procedure for bypassing the small coronary artery branches.
Chalit Cheanvechai, M.D., * Laurence K. Groves, M.D., Suthi Surakiatchanukul, M.D., Nobuyuki Tanaka, M.D., Donald B. Effier, M.D., Earl K. Shirey, M.D., and F. Mason Sones, Jr., M.D., Cleveland, Ohio
SaPhenous vein bypass grafting has gained acceptance for the management of coronary atherosclerosis. The surgical technique is well standardized. Ideally, each graft should have an individual aortic anastomosis; however, many patients have complicated obstructive lesions, such as multiple lesions in the circumflex branches or lesions involving both the anterior descending and diagonal coronary arteries. To bypass these obstructive lesions, multiple grafts and prolonged operative times would have been necessary. A single saphenous vein graft has been used to bypass these lesions in order to decrease the number of anastomoses and the cardiopulmonary bypass time. The dis-
From the Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44105. Received for publication Jan. 6, 1975. Address for reprints: Laurence K. Groves, M.D., Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio. 44106. 'Present address: Chulalongkorn University, Department of Thoracic and Cardiovascular Surgery, Bangkok, Thailand.
tal anastomosis is constructed in end-toside fashion and the middle anastomosis in side-to-side fashion. We call this type of graft a "bridge graft." Operative technique
All operations were performed with the aid of total cardiopulmonary bypass. Interrupted 6-0 silk sutures were utilized in construction of all anastomoses. Grafts to the circumftex branches. A single vein is used to bypass two obstructed circumflex branches by constructing an endto-side anastomosis to the distal circumflex branch and a side-to-side anastomosis to the proximal circumflex branch (Fig. 1). Either anastomosis can be constructed first, depending on the surgeon's preference. The proper length of the graft between these anastomoses is important; the graft should not be too short. To avoid depression of the vein over the side-to-side anastomosis, the vein should be opened obliquely or longitudinally. However,' if a transverse cut in the vein is necessary at the site of the side-to-side anastomosis, the length of the
63
The Journal of
64
Cheanvechai et at.
Thoracic and Cardiavascular Surgery
~
CX BRANCH
Fig. 1. Left coronary artery. Diagram showing a bridge graft to two circumflex (Cx) coronary artery branches. LAD, Left anterior descending.
LAD
Fig. 2. Left coronary artery. Diagram showing a bridge graft to the anterior descending (LAD) and diagonal coronary artery branches. Cx, Circumflex.
incison should not exceed one third of the graft's circumference. Grafts to the anterior descending and diagonal branches. The end-to-side anastomosis is normally constructed on the anterior descending coronary artery and the side-to-side anastomosis on the diagonal branch (Fig. 2). The vein is always opened longitudinally at the site of the side-to-side anastomosis. Kinking of the graft may occur at this level, particularly when the side-to-side anastomosis is constructed on the first diag-
onal branch. However, this problem can be easily corrected by bringing the graft behind the pulmonary artery and aorta through the transverse sinus and then anastomosing it to the right side of the ascending aorta (Fig. 3). When this maneuver is employed, the side branches of the vein must be secured carefully since it is difficult to repair bleeding from a graft placed behind the aorta and pulmonary artery. The bridge graft between the circumflex and diagonal branches is constructed in the same way as that of a graft to two circum-
Volume 70 Number 1 July, 1975
Bridge saphenous vein graft
65
Table I. Types of bridge grafts (August, 1971, to April, 1974) Procedure Cx-Cx Cx-Dg Cx-RCA Cx-LAD Cx-Cx-Cx Cx-Cx-Dg LAD-Dg LAD-LAD Dg-Dg RCA-RCA Cx-Cx, LAD-Dg Total
No.o/patients
96 47 6 I 1 I
79 4 3 9 3 250
Legend: Cx, Circumflex coronary artery. Dg, Diagonal coronary artery. RCA, Right coronary artery. LAD, Left anterior descending coronary artery.
Table II. Postoperative catheterization in
110 patients Condition 0/grafts
Na.ofpatients
Both anastomoses patent One anastomosis patent Both anastomoses occluded
92 (83.6%) 6 ( 5.4%)
12 (10.9%)
flex branches. The bridge graft between the circumflex and right coronary arteries is constructed in end-to-side fashion to the circumflex coronary artery and in side-toside fashion to the right coronary artery. This bridge graft is brought to the aorta alongthe right side of the heart. Construction of a bridge graft to branches of the right coronary artery is done with less frequency. However, in some patients with multiple lesions involving the main right coronary artery and the origin of either the posterior descending or atrioventricular branch, the bridge graft can be constructed in end-to-side fashion to the posterior descending branch or atrioventricular branch and in side-to-side fashion to the main trunk of the right coronary artery (Fig. 4). Material
From August, 1971, to April, 1974, 250 patients received bridge saphenous vein grafts at the Cleveland Clinic Hospital. There were 234 men and 16 women ranging in age from 34 to 68 years. The average
Fig. 3. Diagram showing a bridge graft to the anterior descending and diagonal coronary artery branches passing under the pulmonary artery and aorta through the transverse sinus.
age was 53 years. The types of operations performed are shown in Table I; associated procedures are not included. Most of the grafts were constructed between two circumflex coronary artery branches, circumflex and diagonal coronary artery branches, or anterior descending and diagonal coronary artery branches. Three patients received double bridge grafts, 1 patient received a bridge graft to three branches of the dominant circumflex artery, and 1 patient received a bridge graft to two circumflex and one diagonal coronary artery branches. Morbidity and deaths
Three patients died in the early postoperative period. The hospital mortality rate was 1.2 per cent. Nine patients (3.6 per cent) sustained postoperative myocardial infarctions as confirmed by electrocardiography and serum cardiac enzyme levels. Postoperative catheterization
One hundred ten patients (44 per cent) of the 250 patients who received bridge
The Journal of
66
Cheanvechai et al.
Thoracic and Cardiovascular Surgery
Fig. 4. Right coronary artery. Diagram of a bridge graft constructed to the atrioventricular branch and main right coronary artery.
Fig. S. Postoperative angiogram of a bridge graft showing the end-to-side (E-S) anastomosis and side-to-side (S-S) anastomosis to the circumflex branches. Note the obstructive lesion (arrow) involving the origin of both circumflex branches . A single graft to either one of these branches would not have perfused the other branch.
saphenous vein grafts underwent postoperative catheterization from 1 month to 2 years postoperatively . Ninety-five patients were restudied 1 year after the operation. The average time of restudy in these 110 patients was 1 year . Ninety-two grafts (83.6 per cent) had two patent anastomoses. Six grafts (5.4 per cent) had one patent anastomosis, and 12 grafts (10.9 per cent) had two occluded anastomoses (Table II) . Most of the graft occlusions occurred in the circumflex branches. One hundred twenty-six
associated grafts were restudied in these 110 patients; 106 grafts (84 .1 per cent) were patent. Discussion
Our aim in utilizing the bridge graft technique is to decrease the operative time and the number of anastomoses and to improve graft patency, as previously reported by Flemma, " Bartley,1 and their colleagues, and by Sewell." Furthermore, the obstructive lesions involve multiple coronary artery
Volume 70
67
Bridge saphenous vein graft
Number 1 July, 1975
Fig. 6. Postoperative angiogram of a bridge graft to the anterior descending and diagonal coronary artery branches. Note the anterior descending has a long, obstructive lesion in its middle third portion. Only the distal third is suitable for grafting. This sho rt area of runoff is probably not enough for a single graft to the anterior descending coronary artery. £-5, End -to-side anastomosis. 5-5 , Side-to-side anastomosis.
branches in some patients. Complete revascularization cannot be accomplished in these patients by single bypass grafts (Fig. 5). Theoretically, the bridge graft is ideal for obstructed small coronary artery branches because one small branch, of itself, cannot support an individual graft (Fig. 6). It is a well-known fact that graft patency depends on distal runoff. In our experience, flow measurements are always higher in grafts with two anastomoses (Fig. 7) . Theoretically, the bridge graft should have better patency rates. However, in our series there was no difference in patency when the bridge graft was compared with the associated grafts (83.6 versus 84 .1 per cent) . This is due to the fact that most of the bridge grafts were constructed to smaller coronary artery branches, which in most cases did not have enough runoff to support individual grafts. We do not agree with Bartley's' and Sewell's" idea to use a single graft for two or three major coronary branches. First, when proximal stenosis occurs, either from a technical error or from intimal fibroplasia,v 4," all recipient coronary arteries
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-
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:: '::: Iii I::' Me a n FI 0 W i:;; :iii :: .. 'IIi .... I ' : : ~ Ii; :'11 ... "'. ;.: - ;.:: I: : ,;1; :j ~ ~ ;1'; . 1:: .... Pi! '"11 .. I:!! ... ":: :: TI~ I~ n I;;; ~ I7tt,~ ! :1;; :1:: :Ui !i;; iii; !III : :: : Ii! i l i :I 1:n': ,.1 1 :!! ... ,I:" , , :J;. uu ill ni ~ i!1 1 III' ! ' il; iii 'II' HI : 1: t rr: ''Ii . ' lin :J;, In: j!l i T ,; .. d' j ,:1I Ii', :il' . . " 11 ,al Ii;! 'iii : 11: . . :: ... :::1 1~ i Illi I,!; : : : : HE :: i=i. ... ;i!: ... ... H1: .... .. ... ..f;;" ;' 'j :q; 'ii· !'II
pI! iT !!i: iI!
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Fig. 7. Graphic chart of flow measurements of the bridge graft to the anterior descending and diagonal coronary artery branches demonstrating the decre ase of flow du ring clamping of the graft between the diagonal and anterior descending coronary arteries.
will be jeopardized. The other reason is that it is difficult to find long, uniform saphenous veins. We firmly believe uniform saphenous veins without valves are the best segments for grafting purposes. We recommend use of the bridge graft technique to two circumflex branches, an-
The Journol of
68
Cheanvechai et al.
terior descending and diagonal coronary artery branches, and circumflex and diagonal coronary artery branches. We rarely construct a bridge graft between the major coronary artery branches unless they are small in caliber. Finally, we would like to emphasize that in the bridge graft, the length of the graft between the two anastomoses is important. To avoid depression of the graft over the side-to-side anastomosis, the saphenous vein should be opened routinely in an oblique or longitudinal fashion.
Thoracic and Cardiovascular Surgery
REFERENCES
2
3
4
Summary Bridge saphenous vein grafts were constructed in 250 patients. One hundred ten patients were restudied 1 year postoperatively, and the patency rate was 83.6 per cent. The surgical technique has been described. We recommend this technique for grafting small coronary artery branches.
5 6
Bartley, T. D., Bigelow, J. c., and Page, U. S.: Aortocoronary Bypass Grafting With Multiple Sequential Anastomoses to a Single Vein, Arch. Surg. 105: 915, 1972. Flernrna, R. J., Johnson, W. D., and Lepley, D., Jr.: Triple Aorto-coronary Vein Bypass for Coronary Insufficiency, Arch. Surg. 103: 82, 1971. Grondin, C. M., Meere, C., Castonguay, Y., Lepage, G., and Grondin, P.: Progressive and Late Obstruction of an Aorto-coronary Venous Bypass Graft, Circulation 43: 698, 1971. Hamaker, W. R., Doyle, W. F., O'Connell, T. J., Jr., and Gomez, A. c.. Subintimal Obliterative Proliferation in Saphenous Vein Grafts: A Cause of Early Failure of Aorta to Coronary Artery Bypass Graft, Ann. Thorac. Surg, 13: 488, 1972. Sewell, W. H.: Improved Coronary Vein Graft Patency Rates With Side to Side Anastomoses, Ann. Thorac. Surg. 17: 538, 1974. Vlodaver, Z., and Edwards, J. E.: Pathologic Changes in Aortic-Coronary Arterial Saphenous Vein Grafts, Circulation 44: 719, 1971.
Chalit Cheanvechai, M.D., * Laurence K. Groves, M.D., Suthi Surakiatchanukul, M.D., Nobuyuki Tanaka, M.D., Donald B. Effier, M.D., Earl K. Shirey, M.D., and F. Mason Sones, Jr., M.D., Cleveland, Ohio
SaPhenous vein bypass grafting has gained acceptance for the management of coronary atherosclerosis. The surgical technique is well standardized. Ideally, each graft should have an individual aortic anastomosis; however, many patients have complicated obstructive lesions, such as multiple lesions in the circumflex branches or lesions involving both the anterior descending and diagonal coronary arteries. To bypass these obstructive lesions, multiple grafts and prolonged operative times would have been necessary. A single saphenous vein graft has been used to bypass these lesions in order to decrease the number of anastomoses and the cardiopulmonary bypass time. The dis-
From the Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44105. Received for publication Jan. 6, 1975. Address for reprints: Laurence K. Groves, M.D., Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio. 44106. 'Present address: Chulalongkorn University, Department of Thoracic and Cardiovascular Surgery, Bangkok, Thailand.
tal anastomosis is constructed in end-toside fashion and the middle anastomosis in side-to-side fashion. We call this type of graft a "bridge graft." Operative technique
All operations were performed with the aid of total cardiopulmonary bypass. Interrupted 6-0 silk sutures were utilized in construction of all anastomoses. Grafts to the circumftex branches. A single vein is used to bypass two obstructed circumflex branches by constructing an endto-side anastomosis to the distal circumflex branch and a side-to-side anastomosis to the proximal circumflex branch (Fig. 1). Either anastomosis can be constructed first, depending on the surgeon's preference. The proper length of the graft between these anastomoses is important; the graft should not be too short. To avoid depression of the vein over the side-to-side anastomosis, the vein should be opened obliquely or longitudinally. However,' if a transverse cut in the vein is necessary at the site of the side-to-side anastomosis, the length of the
63
The Journal of
64
Cheanvechai et at.
Thoracic and Cardiavascular Surgery
~
CX BRANCH
Fig. 1. Left coronary artery. Diagram showing a bridge graft to two circumflex (Cx) coronary artery branches. LAD, Left anterior descending.
LAD
Fig. 2. Left coronary artery. Diagram showing a bridge graft to the anterior descending (LAD) and diagonal coronary artery branches. Cx, Circumflex.
incison should not exceed one third of the graft's circumference. Grafts to the anterior descending and diagonal branches. The end-to-side anastomosis is normally constructed on the anterior descending coronary artery and the side-to-side anastomosis on the diagonal branch (Fig. 2). The vein is always opened longitudinally at the site of the side-to-side anastomosis. Kinking of the graft may occur at this level, particularly when the side-to-side anastomosis is constructed on the first diag-
onal branch. However, this problem can be easily corrected by bringing the graft behind the pulmonary artery and aorta through the transverse sinus and then anastomosing it to the right side of the ascending aorta (Fig. 3). When this maneuver is employed, the side branches of the vein must be secured carefully since it is difficult to repair bleeding from a graft placed behind the aorta and pulmonary artery. The bridge graft between the circumflex and diagonal branches is constructed in the same way as that of a graft to two circum-
Volume 70 Number 1 July, 1975
Bridge saphenous vein graft
65
Table I. Types of bridge grafts (August, 1971, to April, 1974) Procedure Cx-Cx Cx-Dg Cx-RCA Cx-LAD Cx-Cx-Cx Cx-Cx-Dg LAD-Dg LAD-LAD Dg-Dg RCA-RCA Cx-Cx, LAD-Dg Total
No.o/patients
96 47 6 I 1 I
79 4 3 9 3 250
Legend: Cx, Circumflex coronary artery. Dg, Diagonal coronary artery. RCA, Right coronary artery. LAD, Left anterior descending coronary artery.
Table II. Postoperative catheterization in
110 patients Condition 0/grafts
Na.ofpatients
Both anastomoses patent One anastomosis patent Both anastomoses occluded
92 (83.6%) 6 ( 5.4%)
12 (10.9%)
flex branches. The bridge graft between the circumflex and right coronary arteries is constructed in end-to-side fashion to the circumflex coronary artery and in side-toside fashion to the right coronary artery. This bridge graft is brought to the aorta alongthe right side of the heart. Construction of a bridge graft to branches of the right coronary artery is done with less frequency. However, in some patients with multiple lesions involving the main right coronary artery and the origin of either the posterior descending or atrioventricular branch, the bridge graft can be constructed in end-to-side fashion to the posterior descending branch or atrioventricular branch and in side-to-side fashion to the main trunk of the right coronary artery (Fig. 4). Material
From August, 1971, to April, 1974, 250 patients received bridge saphenous vein grafts at the Cleveland Clinic Hospital. There were 234 men and 16 women ranging in age from 34 to 68 years. The average
Fig. 3. Diagram showing a bridge graft to the anterior descending and diagonal coronary artery branches passing under the pulmonary artery and aorta through the transverse sinus.
age was 53 years. The types of operations performed are shown in Table I; associated procedures are not included. Most of the grafts were constructed between two circumflex coronary artery branches, circumflex and diagonal coronary artery branches, or anterior descending and diagonal coronary artery branches. Three patients received double bridge grafts, 1 patient received a bridge graft to three branches of the dominant circumflex artery, and 1 patient received a bridge graft to two circumflex and one diagonal coronary artery branches. Morbidity and deaths
Three patients died in the early postoperative period. The hospital mortality rate was 1.2 per cent. Nine patients (3.6 per cent) sustained postoperative myocardial infarctions as confirmed by electrocardiography and serum cardiac enzyme levels. Postoperative catheterization
One hundred ten patients (44 per cent) of the 250 patients who received bridge
The Journal of
66
Cheanvechai et al.
Thoracic and Cardiovascular Surgery
Fig. 4. Right coronary artery. Diagram of a bridge graft constructed to the atrioventricular branch and main right coronary artery.
Fig. S. Postoperative angiogram of a bridge graft showing the end-to-side (E-S) anastomosis and side-to-side (S-S) anastomosis to the circumflex branches. Note the obstructive lesion (arrow) involving the origin of both circumflex branches . A single graft to either one of these branches would not have perfused the other branch.
saphenous vein grafts underwent postoperative catheterization from 1 month to 2 years postoperatively . Ninety-five patients were restudied 1 year after the operation. The average time of restudy in these 110 patients was 1 year . Ninety-two grafts (83.6 per cent) had two patent anastomoses. Six grafts (5.4 per cent) had one patent anastomosis, and 12 grafts (10.9 per cent) had two occluded anastomoses (Table II) . Most of the graft occlusions occurred in the circumflex branches. One hundred twenty-six
associated grafts were restudied in these 110 patients; 106 grafts (84 .1 per cent) were patent. Discussion
Our aim in utilizing the bridge graft technique is to decrease the operative time and the number of anastomoses and to improve graft patency, as previously reported by Flemma, " Bartley,1 and their colleagues, and by Sewell." Furthermore, the obstructive lesions involve multiple coronary artery
Volume 70
67
Bridge saphenous vein graft
Number 1 July, 1975
Fig. 6. Postoperative angiogram of a bridge graft to the anterior descending and diagonal coronary artery branches. Note the anterior descending has a long, obstructive lesion in its middle third portion. Only the distal third is suitable for grafting. This sho rt area of runoff is probably not enough for a single graft to the anterior descending coronary artery. £-5, End -to-side anastomosis. 5-5 , Side-to-side anastomosis.
branches in some patients. Complete revascularization cannot be accomplished in these patients by single bypass grafts (Fig. 5). Theoretically, the bridge graft is ideal for obstructed small coronary artery branches because one small branch, of itself, cannot support an individual graft (Fig. 6). It is a well-known fact that graft patency depends on distal runoff. In our experience, flow measurements are always higher in grafts with two anastomoses (Fig. 7) . Theoretically, the bridge graft should have better patency rates. However, in our series there was no difference in patency when the bridge graft was compared with the associated grafts (83.6 versus 84 .1 per cent) . This is due to the fact that most of the bridge grafts were constructed to smaller coronary artery branches, which in most cases did not have enough runoff to support individual grafts. We do not agree with Bartley's' and Sewell's" idea to use a single graft for two or three major coronary branches. First, when proximal stenosis occurs, either from a technical error or from intimal fibroplasia,v 4," all recipient coronary arteries
!,.;
n~
,ij,
Pulsatile Flow ..
_.... -
;,;
.. ..
."-
,I'
f
'\ -
1\ -
..
- :\
:ii' .. r 21 8 cc/min --
...
..
'q
r:
..
-
oo
"
I::
'::-
oo
..
n
140 ee/m.n
--::1
.. ~ ---, - Q .. _ . , ~ .-
Y- I\; ...;
.
'''I
:: '::: Iii I::' Me a n FI 0 W i:;; :iii :: .. 'IIi .... I ' : : ~ Ii; :'11 ... "'. ;.: - ;.:: I: : ,;1; :j ~ ~ ;1'; . 1:: .... Pi! '"11 .. I:!! ... ":: :: TI~ I~ n I;;; ~ I7tt,~ ! :1;; :1:: :Ui !i;; iii; !III : :: : Ii! i l i :I 1:n': ,.1 1 :!! ... ,I:" , , :J;. uu ill ni ~ i!1 1 III' ! ' il; iii 'II' HI : 1: t rr: ''Ii . ' lin :J;, In: j!l i T ,; .. d' j ,:1I Ii', :il' . . " 11 ,al Ii;! 'iii : 11: . . :: ... :::1 1~ i Illi I,!; : : : : HE :: i=i. ... ;i!: ... ... H1: .... .. ... ..f;;" ;' 'j :q; 'ii· !'II
pI! iT !!i: iI!
oo
'!!
oo
1l
192 ee I m i n
Ii Iii,
jli
; ; ::
105 ee I m i n
Fig. 7. Graphic chart of flow measurements of the bridge graft to the anterior descending and diagonal coronary artery branches demonstrating the decre ase of flow du ring clamping of the graft between the diagonal and anterior descending coronary arteries.
will be jeopardized. The other reason is that it is difficult to find long, uniform saphenous veins. We firmly believe uniform saphenous veins without valves are the best segments for grafting purposes. We recommend use of the bridge graft technique to two circumflex branches, an-
The Journol of
68
Cheanvechai et al.
terior descending and diagonal coronary artery branches, and circumflex and diagonal coronary artery branches. We rarely construct a bridge graft between the major coronary artery branches unless they are small in caliber. Finally, we would like to emphasize that in the bridge graft, the length of the graft between the two anastomoses is important. To avoid depression of the graft over the side-to-side anastomosis, the saphenous vein should be opened routinely in an oblique or longitudinal fashion.
Thoracic and Cardiovascular Surgery
REFERENCES
2
3
4
Summary Bridge saphenous vein grafts were constructed in 250 patients. One hundred ten patients were restudied 1 year postoperatively, and the patency rate was 83.6 per cent. The surgical technique has been described. We recommend this technique for grafting small coronary artery branches.
5 6
Bartley, T. D., Bigelow, J. c., and Page, U. S.: Aortocoronary Bypass Grafting With Multiple Sequential Anastomoses to a Single Vein, Arch. Surg. 105: 915, 1972. Flernrna, R. J., Johnson, W. D., and Lepley, D., Jr.: Triple Aorto-coronary Vein Bypass for Coronary Insufficiency, Arch. Surg. 103: 82, 1971. Grondin, C. M., Meere, C., Castonguay, Y., Lepage, G., and Grondin, P.: Progressive and Late Obstruction of an Aorto-coronary Venous Bypass Graft, Circulation 43: 698, 1971. Hamaker, W. R., Doyle, W. F., O'Connell, T. J., Jr., and Gomez, A. c.. Subintimal Obliterative Proliferation in Saphenous Vein Grafts: A Cause of Early Failure of Aorta to Coronary Artery Bypass Graft, Ann. Thorac. Surg, 13: 488, 1972. Sewell, W. H.: Improved Coronary Vein Graft Patency Rates With Side to Side Anastomoses, Ann. Thorac. Surg. 17: 538, 1974. Vlodaver, Z., and Edwards, J. E.: Pathologic Changes in Aortic-Coronary Arterial Saphenous Vein Grafts, Circulation 44: 719, 1971.