Factors Influencing Patency of Saphenous Vein Grafts Jack A. Roth, M.D., Ramon A. Cukingnan, M.D., B. Greg Brown, M.D., Edward Gocka, Ph.D., a n d Joseph S. Carey, M.D.

ABSTRACT To determine factors affecting saphenous vein graft patency, 218 grafts in 66 unselected patients were studied angiographically 1 year after operation. Fourteen variables were extracted from the angiograms, electrocardiograms, and intraoperative flow measurements to assess their predictive value. Preoperative coronary vessel diameter and degree of proximal stenosis measured angiographically correlated significantly with graft patency. Graft patency for vessels > 1.5 mm in diameter with > 709/0 stenosis was 93% (98 out of 105). Vessel size at operation and the presence of reactive hyperemia > 20 ml per minute also correlated significantly with graft patency. Reactive hyperemia increased significantly as the severity of the vessel stenosis proximal to the graft increased, thus suggesting a mechanism for the improved patency rate of grafts to more stenotic vessels. The patency rate of the end-to-side component of a continuity graft (left anterior descending coronary artery and diagonal or marginal artery in 1 graft) was 100°/~ and of the side-to-side component, 77%. This study shows that the patency rate for saphenous vein grafts compares favorably with the reported patency for internal mammary grafts when critical factors such as vessel size (> 1.5 mm) and degree of stenosis (> 70%) are considered in bypass selection.

survival remains controversial [24], some authors have reported survivals of up to 90% at 5 years [12,17]. Because medical therapy can also achieve symptomatic improvement with comparable long-term survival [241, criteria must be established for the selection of patients who will benefit from aortocoronary bypass operations. Such criteria should allow the selection of patients with a high probability of maintaining long-term graft patency because early graft closure may adversely affect symptomatic relief and possibly long-term survival. The purpose of this study is to identify preoperative and intraoperative variables that influence saphenous vein graft patency. Selecting patients whose coronary anatomy is most suitable for bypass grafting should allow achievement of the highest long-term patency rates. To determine those factors affecting saphenous vein graft patency, the results of postoperative angiography were analyzed in 66 unselected patients with 218 bypass grafts. Patients were studied regardless of symptoms. Fourteen variables were extracted from the angiograms, electrocardiograms, and intraoperative flow measurements to assess their ability to predict graft patency. Materials a n d Methods

Following its introduction in 1968, aortocoronary bypass with saphenous vein has now become an established method of treatment for angina pectoris. Recent studies have shown that this procedure provides significant symptomatic relief and functional improvement in up to 93% of patients [5, 7, 21, 231. Although the influence of coronary bypass grafting on From the Divisions of Thoracic and Cardiovascular Surgery and Cardiology, Wadsworth VA Hospital and UCLA School of Medicine, Los Angeles, CA. Presented at the Fifteenth Annual Meeting of The Society of Thoracic Surgeons, Jan 15-17, 1979, Phoenix, AZ. Address reprint requests to Dr. Cukingnan, 465 N Roxbury Dr, Beverly Hills, CA 90210.

176 0003-4975/79/080176-08$01.25 @ 1978 by Jack A. Roth

Sixty-six men with an average age of 56 years were included in the study. These patients were part of an ongoing prospective study on graft patency and angiographic progression of disease. All operations were performed with standard cardiopulmonary bypass technique using the Olsen pump and Optiflo adult bubble oxygenator. Pump prime consisted of 1.8 liters of balanced electrolyte solution, pH corrected, and contained 75 gm of salt-poor albumin. Packed red cells were added if the hematocrit was less than 30% during perfusion. Pump flows were established at 2.5 L/m2/min.Techniques of myocardial preservation varied dur-

177 Roth et al: Patency of Saphenous Vein Grafts

ing the study period (intermittent anoxic arrest, moderate hypothermia, potassium cardioplegia), but the heart was always arrested during the performance of distal anastomoses. All bypass grafts were reversed saphenous veins. The veins were handled carefully and gently dilated with heparinized blood. There were 168 grafts with single end-to-side anastomoses. Twenty-five combination grafts, each with a side-to-side and end-to-side anastomosis, were performed. All anastomoses were constructed with a continuous suturing technique using 6-0 Prolene. An average of 3.3 grafts per patient was performed. Selective coronary arteriography was performed preoperatively and 1 year after operation in each patient. Arteriograms were performed in both the right and left anterior oblique projections using the method described by Judkins [14]. Several single-plane projections were obtained by the method described by Brown and associates [4]. A Fluorocon 200 system (General Electric) was used, and cineangiograms were taken at thirty frames per second. Left ventricular end-diastolic (LVEDP)and pulmonary artery wedge pressures were measured initially. Left ventriculograms were made before coronary artery catheterization. The degree of vessel stenosis was calculated by estimating the percent reduction in vessel diameter using a computer-based method for analysis of the coronary arteriogram that provided a three-dimensional reconstruction of the diseased segment [41. The variables assessed for each recipient coronary artery included the number of stenoses proximal to the graft site that were 3 50%, the vessel grafted (e.g., right coronary [RCAI or left anterior descending coronary artery [LAD]), the coronary artery diameter estimated angiographically, the location of the anastomosis (proximal, middle, or distal third of the coronary artery), the presence or absence of collateral vessels, the highest grade stenosis proximal to the graft site, and LVEDP. Several variables were measured intraoperatively. Graft flow was measured using a Statham clinical blood flowmeter SP2204. Reactive hyperemia was measured by completely occluding the graft flow for fifteen seconds and

then measuring the flow immediately after release of the occlusion. Coronary vessel diameter was assessed by introducing graduated probes through the coronary arteriotomy. The seventy of disease at the anastomotic site was graded as follows: no disease; mild (one wall involved or intimal thickening); moderate (two walls involved); and severe (circumferential disease). All data were analyzed statistically by preparing 2 X 2 contingency tables and performing chi square analysis using standard computer programs. Two-sided tests were used except when one variable was quantitative and a specific outcome could be tested. A standard computer program was used to compute correlation coefficients by linear regression analysis. The null hypothesis was rejected only if p < 0.05.

Results The aortocoronary graft patency rates associated with the variables measured in the study are shown in Table 1. The coronary artery diameter measured angiographically was the best single preoperative predictor of graft patency. Vessels > 1.5 mm in diameter had a 90% patency rate (172 out of 191) while those 6 1.5 mm had a 52% patency rate (14 out of 27). The severity of the stenosis in the proximal coronary artery in percent 141 also correlated significantly with graft patency (see Table 1).By combining these two factors, saphenous bypass grafts with a high probability of long-term patency could be selected, as shown in Table 2. Grafts to coronary arteries with an angiographic diameter of > 1.5 mm and with > 70% stenosis had a 93% patency rate (98 out of 105). Variables that did not correlate with graft patency included the number of proximal stenoses L 50% (tandem stenoses), the vessel grafted (LAD, RCA, or marginal branch), location of anastomoses, presence or absence of collateral vessels, and LVEDP (see Table 1). Intraoperative measurements confirmed the importance of vessel diameter and distal runoff in predicting graft patency. Vessel diameter measured intraoperatively correlated significantly with vein graft patency (see Table 1). Aortocoronary bypass to recipient coronary arteries > 1.5 mm had a 90% patency rate (149 out of 165) compared with a 65% patency rate for

178 The Annals of Thoracic Surgery Vol 28 No 2 August 1979

Table I . Patency Rate and Statistical Significance for Studied Variables Percentage of Grafts Patent

Variable Angiographic vessel diameter > 1.5 mm Angiographic vessel diameter 6 1.5 mm Proximal stenosis > 70% Proximal stenosis S 70% None or 1 proximal stenosis 3 50% Two or more proximal stenoses 3 50% Recipient vessel, right coronary Recipient vessel, left anterior descending Recipient vessel, diagonal branch Recipient vessel, obtuse marginal branch Anastomosis, proximal third of vessel Anastomosis, middle third of vessel Anastomosis, distal third of vessel Collateral vessel present Collateral vessel absent LVEDP 6 15 mm Hg LVEDP > 15 mm Hg Vessel diameter at operation > 1.5 mm Vessel diameter at operation 6 1.5 mm Reactive hyperemia > 20 mumin Reactive hyperemia 6 20 mYmin Graft flow > 40 mYmin Graft flow 6 40 mYmin No disease at anastomosis Mild disease at anastomosis Moderate disease at anastomosis Severe disease at anastomosis End-to-end anastomosis total Side-to-side anastomosis total Combination grafts, end-to-side anastomosis Combination grafts, side-to-side anastomosis

90 52 90 80 86 85 85 93

p Value

< 0.01 < 0.05 NS NS

84

81 96 86 80 85 86 89 85 90 65 97 79 87 76 74 85 92 88 86 77 100 76

NS NS NS

< 0.01 < 0.01 < 0.06 NS

NS

< 0.02

NS = not statistically significant; LVEDP = left ventricular end-diastolic pressure.

Table 2 . Patency Rate for Bypass Grafts W h e n Recipient Vessels Are Selected by Angiographic Diameter and Percent of Proximal Stenosis

Grafts Total no. No. patent Percent patent Chi square = 22.94 p < 0.0001

Diameter 6 1.5 mm S 70% Proximal Stenosis

Diameter > 1.5 mm > 70% Proximal Stenosis

11 5 45

105 98 93

vessels 6 1.5 mm (17 out of 26). The correlation between angiographic and surgical measurements was significant ( p < 0.01). The presence of reactive hyperemia also showed a significant positive correlation with graft patency. Grafts demonstrating reactive hyperemia of > 20 ml per minute over mean resting flow had a 97% patency rate (59 out of 61) compared with 79% patency (91 out of 115) for grafts with a hyperemic flow of 6 20 ml per minute. Selecting grafts with reactive hyperemia of > 20 ml per minute and vessel size of > 1.5 mm in diameter yielded a 100% patency rate (Table 3). The correlation of mean resting graft flow and patency was of borderline statistical significance (see Table 1). Severity of disease at the

179 Roth et al: Patency of Saphenous Vein Grafts

graft patency. When all anastomoses were analyzed as a group (both single end-to-side and continuity grafts), there was no significant difference in the patency rate for end-to-side Diameter Diameter versus side-to-side anastomosis. However, the =S 1.5 mm, > 1.5 mm, side-to-side anastomosis had a protective influReactive Reactive Hyperemia Hyperemia ence on the end-to-side component of the con6 20 mll > 20 mY tinuity grafts. All of the end-to-side anasmin min Grafts tomoses of the continuity grafts were patent (25 out of 25) compared with an 83% patency rate Tot a1 19 51 No. patent 11 51 (142 out of 170) for the single end-to-side anasPercent patent 58 100 tomosis. Patency of the side-to-side anasChi square = 20.26 tomosis improved as technical proficiency was p < 0.0001 gained with the technique. During the first part of the study (September, 1975, to August, 1976) 69% (11 out of 16) of side-to-side anasTable 4 . Relationship O f Coronary tomoses were patent while during the second Graft, Reactive Hyperemia, and Degree of part of the study (August, 1976, to March, 1977) Coronary Artery Stenosis Proximul to the Gruff 89% (8 out of 9) were patent. This improvement in patency rate (20%) may also be due to better Reactive Hyperemia selection of recipient vessels. Proximal Stenosis (70) 20 mllmin > 20 mYmin Comment =S 70 61 12 The subjective and objective results of coronary > 70 54 48 artery bypass operations could potentially be Chi square = 16.37 improved by better selection of patients. If the p < 0.0001 procedure is done for symptomatic relief and increased longevity, then those patients with anastomotic site had no significant relationship the highest probability of improvement based to vein graft patency. on graft patency should be selected. Clearly, To investigate the possible mechanisms for long-term graft patency is a prerequisite to a the increased patency rate of saphenous vein successful outcome, and therefore, this study grafts to more highly stenotic vessels, the cor- was undertaken to determine if the variables relation between vessel stenosis and reactive measured preoperatively and intraoperatively hyperemia was analyzed. Eighty percent (48 out could predict graft patency. Although several of 60) of vessels with reactive hyperemia of > previous studies have examined single factors 20 ml per minute had proximal stenosis of > influencing patency, we have attempted a com70%. Only 47% of vessels (54 out of 115) with prehensive investigation of many relative facreactive hyperemia of 6 20 ml per minute had a tors and have examined the interrelationships proximal stenosis of > 70% ( p < 0.0001) (Table among them. This study pertains only to 4). This suggests that increasing degrees of saphenous vein grafts, which previous studies coronary artery stenosis result in a vascular bed have shown to have patency rates of 70 to 85% capable of receiving increased flow from the 18, 12, 13, 171. Because late graft closure after 1 vein grafts. This is further supported by the year is unusual, this study could also be useful significant positive correlation of mean resting in predicting long-term graft patency rates graft flow with reactive hyperemia ( p < 0.01). [9, 111. Using multiple variables to determine Mean graft flow also significantly correlated patient survival, Jones and co-workers F131 with recipient vessel size ( p < 0.05). showed improved longevity in patients with Technical factors influenced saphenous vein internal mammary grafts. This improved survi-

Table 3. Patency Rate for Bypass Grafts W h e n Recipient Vessels Are Selected by Angiographic Diameter and Reactive Hyperemia

180 The Annals of Thoracic Surgery Vol 28 No 2 August 1979

Val may be attributed to a better patency rate with internal mammary grafts. Coronary artery diameter determined angiographically by the quantitative technique described by one of us (B. G. B.) was the single best predictor of graft patency [41. Some investigators have noted the relationship between vessel diameter and graft patency [3,15,18,221. Others, however, have not found a significant relationship between these factors [7, 281. In this study, vessels with intraoperative internal diameters < 1.5 mm had a 65% patency rate. Therefore, in patients with otherwise favorable coronary anatomy, small vessels can be bypassed with a fair probability of long-term patency. The use of continuity grafts may increase the patency rate of smaller end-to-side anastomoses by providing a bigger coronary bed. However, if all the coronary arteries have small diameters, careful consideration should be given to other therapeutic modalities since overall long-term graft patency may be significantly reduced. The contribution of proximal coronary artery occlusion to graft patency is controversial. Rees [26] noted that patency was significantly higher in grafts to vessels with 100% occlusion. Blumlein and associates [21 found a Correlation between degree of vessel stenosis and patency. Others did not note this correlation [7,281. Our study demonstrated a small but significant difference (p < 0.05) in patency rate for vessels with higher degrees of proximal stenosis (> 70%). In addition there was a highly significant positive correlation between increasing proximal stenosis and reactive hyperemia. Vessels with higher degrees of stenosis produced greater ischemia in the distal vascular bed, probably related to increased flow resistance at the stenosis and pressure drop distally. Thus, the distal vascular bed dilates, distal runoff is increased, and flow through the graft is augmented following revascularization. Reactive hyperemia correlated well with graft patency. Marco and associates [201 also noted a correlation between these two factors. The resting graft flow demonstrated only borderline significance in correlating with graft patency. Others have found a significant correlation between low graft flow and reduced patency

[15,16,20,22,281. The lack of correlation in our study may be due to the small number of grafts with flows of < 20 ml per minute (3 grafts). Both Marco and co-workers [20] and Kaiser and associates [15] noted most of their occluded grafts had flows of < 20 ml per minute. Continuity or combination grafts achieved a patency rate comparable to single end-to-side grafts in our study. Combination grafts were described by Bartley and associates [l] in 1972, and others since then have reported improved patency with multiple side-to-side anastomoses [lo, 19,271. Technique is an important factor in the success of this type of graft. We utilized the "diamond-shaped" side-to-side anastomosis similar to that described by Grondin and Limet [lo]. Our data demonstrate that as experience with this graft technique increases, patency also increases. In addition, the side-to-side anastomosis exerts a protective effect on the end-to-side anastomosis, possibly by increasing total graft flow [lo]. The severity of disease at the anastomosis did not affect graft patency, perhaps indicating that diameter and degree of stenosis rather than the quality of the vascular wall determine patency. Therefore, even if severe disease is noted after the arteriotomy is made, a successful anastomosis can be constructed except in very small vessels (< 1.5 mm). In conclusion, the best preoperative predictors of saphenous vein graft patency are angiographic vessel diameter and the degree of coronary artery stenosis. Intraoperatively, reactive hyperemia and vessel diameter correlate best with long-term patency. The use of continuity grafts might also improve graft patency rates. This study has enabled us to isolate some of the factors influencing saphenous graft patency and may be useful in the selection of patients for bypass grafting. With proper selection, a patency rate of 93% can be achieved, comparable to that reported for the internal mammary graft. Improvement in patency rates may ultimately improve symptomatic relief and patient survival. References 1. Bartley TD,Bigelow JC, Page US: Aortocoronary bypass grafting with multiple sequential anastomoses to a single vein. Arch Surg 105:915,1972

181 Roth et al: Patency of Saphenous Vein Grafts

2. Blumlein SL, Anderson AJ, Barboriak JJ, et al: Preoperative risk factors and aorta-coronary bypass graft patency. J Thorac Cardiovasc Surg 72:778, 1976 3. Bourassa MD, Lesperance J, Compeau L, et al: Factors influencing patency of aortocoronary vein grafts. Circulation 45:Suppl 13-79, 1972 4. Brown GB, Bolson E, Frimer M, et al: Quantitative coronary arteriography: estimation of dimensions, hemodynamic resistance, and atheroma mass of a coronary artery lesion using the arteriogram and digital computation. Circulation 55:329, 1977 5. Carey JS, Cukingnan RA, Groner GF, et al: Probability of s m i v a l after coronary bypass surgery in Veterans Administration and community hospitals. J Thorac Cardiovasc Surg 77:39, 1979 6. Diethrich EB, Prion GW: Factors affecting intraoperatively determined aortocoronary vein graft blood flow in 109 patients. Vasc Surg 9:78, 1975 7. Formanek A, Nicoloff D, Lillehei RC, et al: Angiographic analysis of factors influencing coronary artery bypass patency. Fortschr Geb Roentgen Nuklearmed 120:133, 1974 8. Green GE: Internal mammary artery-to-coronary artery anastomosis: three-year experience with 165 patients. Ann Thorac Surg 14:260, 1972 9. Grondin CM, Lesperance J, Bourassa MD, et al: Serial angiographic evaluation in 60 consecutive patients with aortocoronary artery vein grafts 2 weeks, 1 year and 3 years after operation. J Thorac Cardiovasc Surg 67:1, 1974 10. Grondin CM, Limet R: Sequential anastomoses in coronary artery grafting: technical aspects and early and late angiographic results. Ann Thorac Surg 23:1, 1977 11. Iscoitz SB, Redwood DR, Stinson EB, et al: Saphenous vein bypass grafts: long-term patency and effect on the native coronary circulation, Am J Cardiol36:739, 1975 12. Isom OW, Spencer FC, Glassman E, et al: Does coronary bypass increase longevity? J Thorac Cardiovasc Surg 75:28, 1978 13. Jones JW, Oschner JL, Mills NL, et al: Impact of multiple variables on operative and extended survival following coronary artery surgery. Surgery 83:20, 1978 14. Judkins M E Selective coronary arteriography: a percutaneous femoral technic. Radiology 89:815, 1967 15. Kaiser GC, Barner HB, Willman VL, et al: Aortocoronary bypass grafting. Arch Surg 105:319, 1972 16. Kayser KL, Johnson WD: Patency of coronary bypass grafts (letter to the editor). J Thorac Cardiovasc Surg 73:321, 1977 17. Lawrie GM, Moms GC Jr, Howell JF, et a1 The results of coronary bypass more than five years after operation in 434 patients: clinical, exercise

treadmill and angiographic correlations. Am J Cardiol40:665, 1977 18. Lesperance J, Bourassa MG, Biron P, et al: Aorta to coronary artery saphenous vein grafts. Am J Cardiol30:459, 1972 19. Limet R: Interet de l'anastomose latera-laterale en chirurgie coronaire. Acta Chir Belg 75:390, 1976 20. Marco JD, Barner HB, Kaiser GC, et al: Operative flow measurements and coronary bypass graft patency. J Thorac Cardiovasc Surg 71545, 1976 21. Mathur VS, Guinn GA: Prospective randomized study of coronary bypass surgery in stable angina: the first hundred patients. Circulation 51:Suppl 1:133, 1975 22. Mehta J, Hamby RI, Aintablican A, et al: Preoperative coronary angiographic prediction of bypass flow and short-term patency. Cathet Cardiovasc Diagn 1:381, 1975 23. Mundth ED, Austen WG: Surgical measures for coronary heart disease. N Engl J Med 293:13, 75, 124, 1975 24. Murphy ML, Hultgren HN, Detre K, et al: Treatment of chronic stable angina. N Engl J Med 297:621, 1977 25. Najmi M, Ushiyama K, Blanca G, et al: Results of aortocoronary artery saphenous vein bypass surgery for ischemic heart disease. Am J Cardiol 33:41, 1974 26. Rees S: The watershed: a factor in coronary vein graft occlusion. Br Heart J 38:197, 1976 27. Sewell WH: Improved coronary vein graft patency rates with side-to-side anastomoses. Ann Thorac Surg 17:538, 1974 28. Walker JA, Friedberg HD, Flemma RJ, et al: Determinants of angiographic patency of aortocoronary vein bypass grafts. Circulation 45: Suppl I:I-86, 1971

Discussion (Houston, TX): I think this is a very important paper. Basically, the findings reported are in agreement with our experience, which had a similar overall patency. Also if we make a better selection of patients, we find patency similar to that obtained with the internal mammary grafts. If we use large arteries with good runoff and anastomose veins to them, we will get good patency rates; conversely, we will have bad results with smaller vessels. We also have been interested in the influence of the severity of proximal stenosis on patency, and have not been able to demonstrate any difference between vessels with stenosis of more than 70% and 100%. Once a severe stenosis is involved, I don't think the degree of severity matters much. But certainly, mildly stenosed vessels do have a lower patency either because of lack of distal ischemia or because of competitive flow. DR. GERALD M. LAWRIE

182 The Annals of Thoracic Surgery Vol 28 No 2 August 1979

We are interested in this problem because when we made a detailed study of the progression of disease over a 5-year period, we found that mild lesions rarely progress. It was far more common for new lesions with stenosis of more than 70% to appear in the vessels than for mild lesions to progress. If we combine our data with those of Dr. Roth and look at the small secondary and tertiary branches which have diameters usually less than 1 mm and which often have only mild stenosis, we really cannot see any justification for applying grafts to these vessels, especially since when the grafts occlude, they not infrequently take the branch with them. We believe that multiple grafts to excess are not really desirable. If a lesion appears angiographically to have stenosis of 50%, thallium scanningcan be used to confirm W a d a omniview magnifying glasses. this. Before we operate on such patients, we prefer to demonstrate distal ischemia during exercise. For illumination of the operative field, indeI do disagree with Dr. Roth on one point. We try to pendent fiberoptic lights are to be available. They avoid opening a coronary artery in an area of disease. can be attached to a chest wall retractor or incorpoAnyone who has done many vascular operations rated into the glasses frame. They will obviate the would recognize the desirability of this, and a need for headlights, which are very cumbersome. number of papers have been published showing pathological specimens in which graft dissections in DR. EDWARD B. DIETHRICH (Phoenix, AZ):We also the native coronary artery were initiated by the at- have been interested in the factors affecting longtachment of grafts to the areas of disease. I think it is term patency of bypass grafts and would like to be important to try to seek out soft areas, present in able to assess the patient’s potential for graft patency most coronary arteries, for graft attachment. before operation. I think the study by Dr. Roth and Did the authors study the underlying native circu- his associates does make a contribution to this field. lation? We think it very important to look not only at There are just three points that I would like to make crude graft patencies but also to what has actually based upon our 7-year experience in evaluating critehappened to the underlying artery. After all, as far as ria for long-term graft patency. the patient is concerned, it is how the blood is getWe have found that of all the factors so far identing to the tissues that is important, and the graft and tified, the most important is the intraoperative arthe artery form a common unit. And I want to em- teriogram. We have studied more than 100 patients phasize the fact that a small number of grafts when with intraoperative arteriography and correlated the findings with repeat arteriographic studies made they do occlude, do destroy the underlying artery. I think the results of this study enhance our ability within 3 years. We believe the ten-point grading to predict who should be operated on. At the same evaluation derived from the intraoperative study is time, I think it is important to remember that the the most important factor. This grading system aspatients with the most advanced disease are, in gen- sesses the quality of the anastomosis, the antegrade eral, the patients most in need of operation; and and retrograde flow, the presence or absence of distal while the factors measured by Dr. Roth and his col- atherosclerosis, and the size of the coronary artery. leagues are important guidelines for predicting the The second point concerns reactive hyperemia. We outcome of the operation, I think we should not be have found resting flow studies to be very misleaddissuaded to operate on some of these patients be- ing. Our biomedical engineers have developed an cause of the poorer chances of success. electromagnetic flow probe that can be put around the vein graft and positioned and removed similarly DR. JURO WADA (Tokyo, Japan): I believe that sur- to a chest tube. We have monitored the flow for the geons need better visualization of the surgical first forty-eight hours after operation, and have disanatomy when they are doing operations. Especially covered that there can be increases in flow of more in microvascular operations, good magnification that than l0Oo/o of that measured during the operation. This shows that the intraoperative flow study may is not cumbersome is mandatory. To meet this need I have devised the Wada om- not be as reliable an indicator of flow dynamics as has niview magnifying glasses (Figure). They are trifocal been thought; hence, I think the idea of using reacand light weight, and all parts are made of clear, tive hyperemia is quite promising. The third point I want to make concerns the influtransparent plastic. Half glasses in this design are ence of metabolic factors on graft patency. In our also available. I have a pilot pair for my own use.

183 Roth et al: Patency of Saphenous Vein Grafts

studies, some metabolic factors have been found to be as important as the technical ones. For instance, patients with type I1 or type 111 lipoprotein abnormalities demonstrate an increased incidence of early graft closure and problems with the graft itself. I would like to ask Dr. Roth whether metabolic factors have demonstrated any influence in his series. DR. ROTH: I would like to thank the discussants for their very interesting and incisive comments. Dr. Liddle, in this particular series endarterectomy generally was not done. If a large atheroma was encountered, it was excluded and was used as part of the anastomosis. Dr. Lawrie, the degree of proximal stenosis is probably not all that significant a determinant. In our series, the difference was only 10% between grafts to vessels with greater than 70% proximal stenosis and grafts to those with less than 70% stenosis. It is probably not the degree of proximal stenosis per se but rather its influence on the distal circulation that is important. Our data demonstrate that increasing proximal stenosis does increase the reactive hyperemia of the distal vascular bed. We do not advocate opening the coronary arteries

in an area that is heavily diseased. Nevertheless, we have found that performing an anastomosis in a severely diseased vessel does not influence the patency rate. In our series there was no significant difference in patency rates among severely diseased, moderately diseased, and mildly diseased vessels. If a vessel is inadvertently opened in an area that is heavily diseased, this does not deter us from doing the bypass. If the vessel is found to be diffusely diseased, again, this would not deter us from doing the graft. We have looked at the native coronary circulation as well. Dr. Greg Brown has done the angiographic studies, and he finds little progression of disease at the anastomotic site or distal to the anastomosis. Most of the disease progression occurs in the portion of the coronary artery proximal to the anastomosis. Dr. Diethrichs observations are extremely interesting. We take great care to make sure that our resting flows are reproducible in the operating room. They are measured multiple times until a stable value is achieved. We believe these values are reproducible, but I think his observations are very pertinent. We have not looked at metabolic factors in the patients in this study.

Factors influencing patency of saphenous vein grafts.

Factors Influencing Patency of Saphenous Vein Grafts Jack A. Roth, M.D., Ramon A. Cukingnan, M.D., B. Greg Brown, M.D., Edward Gocka, Ph.D., a n d Jos...
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