Radial-Artery Coronary Bypass Grafts
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《新英格兰医药杂志》
To the Editor: Desai et al. (Nov. 25 issue) conducted a well-designed trial comparing radial-artery and saphenous-vein grafts.1 In contrast to our conclusions,2 they conclude that radial arteries had superior angiographic outcomes. However, on examination, our two reports are quite similar.
The primary outcome of their study, graft occlusion, does not take into account severely diseased grafts. If this outcome were included, there would be no difference between the two types of graft. The mechanism of graft failure probably differs: the radial-artery grafts become severely diseased, whereas the vein grafts occlude. Thus, the report by Desai et al. would be the third one to show that radial-artery grafts have angiographic outcomes that are similar to those of vein grafts.1,2,3
The authors suggest that radial-artery grafts may be protected from the progressive atherosclerosis that affects vein grafts. However, the rate at which graft patency deteriorates is similar for the two types of grafts in long-term follow-up.2,3 The long-term angiographic outcomes of radial-artery grafts remain an area of active investigation. We eagerly await the authors' five-year data and data from other studies.
Umesh N. Khot, M.D.
Indiana Heart Physicians
Indianapolis, IN 46237
khot@cvresearch.net
Daniel T. Friedman, D.O.
Metrohealth Medical Center
Cleveland, OH 44109
Stephen G. Ellis, M.D.
Cleveland Clinic Foundation
Cleveland, OH 44195
References
Desai ND, Cohen EA, Naylor CD, Fremes SE. A randomized comparison of radial-artery and saphenous-vein coronary bypass grafts. N Engl J Med 2004;351:2302-2309.
Khot UN, Friedman DT, Pettersson G, Smedira NG, Li J, Ellis SG. Radial artery bypass grafts have an increased occurrence of angiographically severe stenosis and occlusion compared with left internal mammary arteries and saphenous vein grafts. Circulation 2004;109:2086-2091.
Zacharias A, Habib RH, Schwann TA, Riordan CJ, Durham SJ, Shah A. Improved survival with radial artery versus vein conduits in coronary bypass surgery with left internal thoracic artery to left anterior descending artery grafting. Circulation 2004;109:1489-1496.
To the Editor: I offer a word of caution about using radial-artery grafts for coronary-artery bypass in patients with renal disease. More and more patients with diabetes, multiple-site atherosclerosis, or both will have progression to renal failure and will require hemodialysis. The harvesting of a radial artery precludes the use of the ipsilateral arm for vascular access for hemodialysis, because of the high risk of distal ischemia; as a result, the opportunities for arteriovenous fistula or bypass placement are limited. Such patients will then face the risks associated with the long-term use of central-venous catheters. I suggest taking into account the problems of vascular access for hemodialysis when planning coronary bypass surgery in patients at risk for renal failure.
Alberto Montoli, M.D.
A.O. Ospedale Niguarda Ca' Granda
20162 Milan, Italy
montalberto@tiscali.it
The authors reply: Dr. Khot and colleagues state that saphenous-vein grafts are prone to occlusion, whereas radial-artery grafts become "severely diseased." We disagree that radial-artery grafts, which are diffusely narrowed, are in fact severely diseased. It is well documented that arterial conduits, particularly the radial arteries, adjust their luminal diameter on the basis of the flow characteristics of the native coronary vessel. Such narrowed grafts may still be functional and may remain capable of responding to increased myocardial oxygen demand. The long-term results of such grafts are ill defined, and a previous cohort study that included sequential angiographic follow-up suggested that the radial artery is relatively protected from atherosclerosis as compared with saphenous-vein grafts.1
In our trial, we identified a stronger relationship between radial-artery–graft patency and the severity of proximal native-vessel stenosis than has previously been documented. We found that radial arteries that were grafted to native vessels with 90 percent stenosis or greater had an occlusion rate of only 5.9 percent, whereas radial arteries grafted to native vessels with less than 90 percent stenosis had an occlusion rate of 11.8 percent (P=0.03). We also found that the majority of patent grafts with a Thrombolysis in Myocardial Infarction (TIMI) flow grade of 1 or 2 (i.e., severely diseased) were grafted to native coronary vessels with less than 90 percent stenosis. Hence, the preferential selection of target vessels with a very high grade of stenosis can improve radial-artery patency substantially, an effect not seen in saphenous-vein grafts.
In response to Dr. Montoli's comments, we agree that radial-artery grafts should not be used routinely in patients with severe renal insufficiency. Our study protocol specifically excluded patients with a serum creatinine level higher than 180 μmol per liter, primarily to prevent renal complications if cardiac catheterization is repeated. In addition to concern about vascular access for hemodialysis, previous investigations have shown that concomitant peripheral vascular disease, which is more common in patients with renal insufficiency than in those without renal insufficiency, is a risk factor for radial-artery graft occlusion.2 Hence, we avoid radial-artery grafting in these patients.
Nimesh D. Desai, M.D.
Stephen E. Fremes, M.D.
Sunnybrook and Women's College Health Sciences Centre
Toronto, ON M4N 3M5, Canada
stephen.fremes@sw.ca
References
Possati G, Gaudino M, Prati F, et al. Long-term results of the radial artery used for myocardial revascularization. Circulation 2003;108:1350-1354.
Ruengsakulrach P, Sinclair R, Komeda M, Raman J, Gordon I, Buxton B. Comparative histopathology of radial artery versus internal thoracic artery and risk factors for development of intimal hyperplasia and atherosclerosis. Circulation 1999;100:Suppl II:II-139.
The primary outcome of their study, graft occlusion, does not take into account severely diseased grafts. If this outcome were included, there would be no difference between the two types of graft. The mechanism of graft failure probably differs: the radial-artery grafts become severely diseased, whereas the vein grafts occlude. Thus, the report by Desai et al. would be the third one to show that radial-artery grafts have angiographic outcomes that are similar to those of vein grafts.1,2,3
The authors suggest that radial-artery grafts may be protected from the progressive atherosclerosis that affects vein grafts. However, the rate at which graft patency deteriorates is similar for the two types of grafts in long-term follow-up.2,3 The long-term angiographic outcomes of radial-artery grafts remain an area of active investigation. We eagerly await the authors' five-year data and data from other studies.
Umesh N. Khot, M.D.
Indiana Heart Physicians
Indianapolis, IN 46237
khot@cvresearch.net
Daniel T. Friedman, D.O.
Metrohealth Medical Center
Cleveland, OH 44109
Stephen G. Ellis, M.D.
Cleveland Clinic Foundation
Cleveland, OH 44195
References
Desai ND, Cohen EA, Naylor CD, Fremes SE. A randomized comparison of radial-artery and saphenous-vein coronary bypass grafts. N Engl J Med 2004;351:2302-2309.
Khot UN, Friedman DT, Pettersson G, Smedira NG, Li J, Ellis SG. Radial artery bypass grafts have an increased occurrence of angiographically severe stenosis and occlusion compared with left internal mammary arteries and saphenous vein grafts. Circulation 2004;109:2086-2091.
Zacharias A, Habib RH, Schwann TA, Riordan CJ, Durham SJ, Shah A. Improved survival with radial artery versus vein conduits in coronary bypass surgery with left internal thoracic artery to left anterior descending artery grafting. Circulation 2004;109:1489-1496.
To the Editor: I offer a word of caution about using radial-artery grafts for coronary-artery bypass in patients with renal disease. More and more patients with diabetes, multiple-site atherosclerosis, or both will have progression to renal failure and will require hemodialysis. The harvesting of a radial artery precludes the use of the ipsilateral arm for vascular access for hemodialysis, because of the high risk of distal ischemia; as a result, the opportunities for arteriovenous fistula or bypass placement are limited. Such patients will then face the risks associated with the long-term use of central-venous catheters. I suggest taking into account the problems of vascular access for hemodialysis when planning coronary bypass surgery in patients at risk for renal failure.
Alberto Montoli, M.D.
A.O. Ospedale Niguarda Ca' Granda
20162 Milan, Italy
montalberto@tiscali.it
The authors reply: Dr. Khot and colleagues state that saphenous-vein grafts are prone to occlusion, whereas radial-artery grafts become "severely diseased." We disagree that radial-artery grafts, which are diffusely narrowed, are in fact severely diseased. It is well documented that arterial conduits, particularly the radial arteries, adjust their luminal diameter on the basis of the flow characteristics of the native coronary vessel. Such narrowed grafts may still be functional and may remain capable of responding to increased myocardial oxygen demand. The long-term results of such grafts are ill defined, and a previous cohort study that included sequential angiographic follow-up suggested that the radial artery is relatively protected from atherosclerosis as compared with saphenous-vein grafts.1
In our trial, we identified a stronger relationship between radial-artery–graft patency and the severity of proximal native-vessel stenosis than has previously been documented. We found that radial arteries that were grafted to native vessels with 90 percent stenosis or greater had an occlusion rate of only 5.9 percent, whereas radial arteries grafted to native vessels with less than 90 percent stenosis had an occlusion rate of 11.8 percent (P=0.03). We also found that the majority of patent grafts with a Thrombolysis in Myocardial Infarction (TIMI) flow grade of 1 or 2 (i.e., severely diseased) were grafted to native coronary vessels with less than 90 percent stenosis. Hence, the preferential selection of target vessels with a very high grade of stenosis can improve radial-artery patency substantially, an effect not seen in saphenous-vein grafts.
In response to Dr. Montoli's comments, we agree that radial-artery grafts should not be used routinely in patients with severe renal insufficiency. Our study protocol specifically excluded patients with a serum creatinine level higher than 180 μmol per liter, primarily to prevent renal complications if cardiac catheterization is repeated. In addition to concern about vascular access for hemodialysis, previous investigations have shown that concomitant peripheral vascular disease, which is more common in patients with renal insufficiency than in those without renal insufficiency, is a risk factor for radial-artery graft occlusion.2 Hence, we avoid radial-artery grafting in these patients.
Nimesh D. Desai, M.D.
Stephen E. Fremes, M.D.
Sunnybrook and Women's College Health Sciences Centre
Toronto, ON M4N 3M5, Canada
stephen.fremes@sw.ca
References
Possati G, Gaudino M, Prati F, et al. Long-term results of the radial artery used for myocardial revascularization. Circulation 2003;108:1350-1354.
Ruengsakulrach P, Sinclair R, Komeda M, Raman J, Gordon I, Buxton B. Comparative histopathology of radial artery versus internal thoracic artery and risk factors for development of intimal hyperplasia and atherosclerosis. Circulation 1999;100:Suppl II:II-139.