Off-Pump versus On-Pump Coronary Bypass Surgery
http://www.100md.com
《新英格兰医药杂志》
To the Editor: In the article by Khan et al. (Jan. 1 issue),1 the conclusion regarding the inferiority of graft patency in patients who have undergone off-pump bypass surgery is premature. Before initiation of the study, each of the two participating surgeons had performed, on average, only 49 off-pump graft procedures, and they performed a total of only 75 such procedures (in 27 patients) during the trial. The study identified disparate reductions in overall patency for grafts in the right-coronary-artery distribution and for those involving radial-artery conduits, as compared with previously published results.2 There is a direct correlation between the number of procedures performed by a surgeon and the clinical outcome,3,4 suggesting that patency rates are a function of surgical experience. In addition, the authors did not use apical suction devices or routine intracoronary shunting, both of which facilitate technical precision in the creation of an anastomosis, particularly in difficult-to-graft territories of the heart. Moreover, they do not mention the use of a blower mister, which also allows precise coronary suturing. Contrary to the authors' statement, we believe that surgeons' skill, experience, and use of all the available technological adjuncts are of paramount importance in the achievement of appropriate graft-patency rates in off-pump coronary-artery bypass grafting.
Brian J. deGuzman, M.D.
Mahesh H. Subramaniam, M.D.
Lahey Clinic Medical Center
Burlington, MA 01805
brian.j.deguzman@lahey.org
References
Khan NE, DeSouza A, Mister R, et al. A randomized comparison of off-pump and on-pump multivessel coronary-artery bypass surgery. N Engl J Med 2004;350:21-28.
Ochi M, Hatori N, Kanno S, Yamada K, Saji Y, Tanaka S. Coronary artery bypass grafting without cardiopulmonary bypass: a five-year experience. J Nippon Med Sch 2003;70:157-164.
Song HK, Petersen RJ, Sharoni E, Guyton RA, Puskas JD. Safe evolution towards routine off-pump coronary artery bypass: negotiating the learning curve. Eur J Cardiothorac Surg 2003;24:947-952.
Brown PP, Mack MJ, Simon AW, et al. Comparing clinical outcomes in high-volume and low-volume off-pump coronary bypass operation programs. Ann Thorac Surg 2001;72:S1009-S1015.
To the Editor: We congratulate Khan et al. for completing one of the few randomized studies comparing off-pump and on-pump coronary-artery bypass surgery. However, it is our opinion that to conclude that off-pump surgery is inferior to conventional bypass surgery on the basis of graft patency at three months in only 43 patients is premature and possibly misleading. The crux of any randomized surgical trial is the surgeons' equivalent proficiency with the techniques being evaluated. One could conclude that experience consisting of only 98 off-pump procedures, which require a different skill set, during the two years before the study (for an average of 25 procedures per surgeon per year) might bias the results against the off-pump cohort in terms of equivalent expertise. Additional factors that could have negatively affected patency in those who underwent off-pump surgery include the relatively low dose of intraoperative heparin, the absence of aggressive antiplatelet therapy with clopidogrel postoperatively, and the failure to use new suction devices to optimize exposure. Although this study is in contradistinction to the preponderance of those in the published literature, it does again highlight the need for a large, randomized trial with sufficient power to provide conclusive answers regarding off-pump coronary-artery bypass surgery.
Todd M. Dewey, M.D.
Mitchell J. Magee, M.D.
Michael J. Mack, M.D.
Cardiopulmonary Research Science and Technology Institute
Dallas, TX 75230
To the Editor: Khan et al. report a decrease of 10 percentage points in the rate of graft patency with off-pump as compared with on-pump coronary-artery bypass surgery. Most of the graft occlusions in the off-pump group occurred in the radial arteries, for which the rate of patency was only 76 percent. This finding is unexpected, since radial arteries have large luminal diameters and thick muscular walls, which facilitate the construction of anastomoses. A previous analysis of 523 radial-artery grafts performed off-pump revealed a 97.9 percent rate of early graft patency.1
Important determinants of radial-artery graft patency not discussed in the article include the severity of target-vessel stenosis (i.e., competitive flow), perioperative use of vasoconstrictors, and use of calcium-channel blockers.2,3 Recent studies have shown that graft occlusion is twice as likely when the radial artery is anastomosed to a target vessel with less than 70 percent stenosis.2,3 In the study by Khan et al., since the location of the target artery was not randomized, systematic differences in target-vessel selection may have influenced patency. The authors do not specify whether graft occlusion was due to focal stenosis or diffuse graft spasm. Concluding that radial-artery patency is poorer with off-pump surgery than with on-pump surgery on the basis of this study would be highly presumptuous.
Nimesh D. Desai, M.D.
Stephen E. Fremes, M.D.
Sunnybrook and Women's College Health Sciences Centre
Toronto, ON M4N 3M5, Canada
nimesh.desai@utoronto.ca
References
Kobayashi J, Tagusari O, Bando K, et al. Total arterial off-pump coronary revascularization with only internal thoracic artery and composite radial artery grafts. Heart Surg Forum 2002;6:30-37.
Desai ND, Cohen EA, Fremes SE. One year results of the Multi-center Radial Artery Patency Study. Circulation 2003;108:Suppl IV:IV-390. abstract.
Possati G, Gaudino M, Prati F, et al. Long-term results of the radial artery used for myocardial revascularization. Circulation 2003;108:1350-1354.
To the Editor: Khan et al. report that troponin T levels 6 and 12 hours after on-pump coronary surgery were higher than those after off-pump surgery. Early, transient elevation of the plasma troponin T level represents the release of cytosolic troponin T and does not necessarily reflect myocyte death. A substantial and unspecific elevation of the troponin T level occurs early after coronary surgery, even in patients who have no evidence of permanent myocardial injury.1 Myocardial necrosis leads to the breakdown of structurally bound troponin T and protracted elevation of the plasma troponin T level. The results recorded by Khan et al. at 72 hours provide a better estimate of permanent tissue loss than do the early recordings. These results suggest that there was a minor and similar degree of myocardial injury regardless of whether the procedure was performed on-pump or off-pump. Previous claims of lesser degrees of myocardial injury after off-pump surgery may not be justified. Do the authors think that the trade-off in inferior graft patency justifies off-pump coronary surgery in other than selected high-risk patients?
Rolf Svedjeholm, M.D., Ph.D.
Lars-G?ran Dahlin, M.D., Ph.D.
University Hospital Linkoping
SE-581 85 Linkoping, Sweden
rolf.svedjeholm@lio.se
References
Dahlin L-G, K?gedal B, Nylander E, Olin C, Rutberg H, Svedjeholm R. Unspecific elevation of plasma troponin-T and CK-MB after coronary surgery. Scand Cardiovasc J 2003;37:283-287.
The authors reply: Although we agree with deGuzman and Subramaniam, who suggest that there is a learning curve among surgeons performing off-pump coronary-artery bypass procedures, ours was a pilot randomized, controlled study. We suggest that inferior rates of patency may be the price to pay when off-pump surgery is introduced into a surgeon's practice, but that patency rates may improve with experience and the use of technological adjuncts. Such factors should influence our efforts to obtain informed consent from patients. Intracoronary shunts and blower misters were used in a minority of our graft procedures (43 of 333, or 13 percent), but apical suction devices were not available to us at the time.
The evaluation of a new surgical technique is controversial, but the randomized, controlled trial is the most robust test available. If the trial is performed too early, it can reasonably be argued that techniques have not matured and experience is limited; if it is performed too late and the period of surgical equipoise has expired, recruitment may be difficult on ethical grounds. This point is implicit in Dewey and colleagues' comments.
Desai and Fremes remark on the reduced rate of patency in our radial-artery grafts. Although we do not have data on target-vessel stenosis, we did not graft vessels with less than 70 percent stenosis. Our radial grafts were removed without the use of diathermy and stored for periods of up to 45 minutes in verapamil solution (2 mg per 100 ml of Ringer's solution), and all the patients received diltiazem at a dose of 60 to 90 mg twice daily from the day of surgery until six weeks postoperatively. Hirose et al.,1 who investigated the use of the gastroepiploic artery, reported three-year patency rates of 91.3 percent for the radial artery as compared with five-year rates of 97.0 percent for the left internal thoracic artery and 88.5 percent for the saphenous vein.
We appreciate the comments of Svedjeholm and Dahlin and believe that inferior graft patency may be justified in high-risk elderly patients to reduce the risk of stroke.2 Since our study was completed, Gaudino et al.3 have reported a significantly higher rate of recurrence of ischemia with off-pump surgery (recurrences in 71 of 184 patients ) than with on-pump surgery (recurrences in 19 of 103 patients , P<0.001). In a large audit of more than 68,000 patients in New York, Racz et al.4 showed that patients undergoing on-pump surgery had better long-term survival and greater freedom from revascularization than patients undergoing off-pump surgery. We would welcome a large randomized, controlled trial to test the long-term efficacy of off-pump surgery.
Natasha E. Khan, M.R.C.S.
Anthony C. DeSouza, F.R.C.S.
Royal Brompton and Harefield NHS Trust
London SW3 6NP, United Kingdom
John R. Pepper, M.Chir.
Imperial College of Science, Technology, and Medicine
London SW3 6LY, United Kingdom
References
Hirose H, Amano A, Takanashi S, Takahashi A. Coronary artery bypass grafting using the gastroepiploic artery in 1,000 patients. Ann Thorac Surg 2002;73:1371-1379.
Al-Ruzzeh S, Athanasiou T, George S, et al. Is the use of cardiopulmonary bypass for multivessel coronary artery bypass surgery an independent predictor of operative mortality in patients with ischemic left ventricular dysfunction? Ann Thorac Surg 2003;76:444-452.
Gaudino M, Glieca F, Alessandrini F, et al. High risk coronary artery bypass patient: incidence, surgical strategies, and results. Ann Thorac Surg 2004;77:574-580.
Racz MJ, Hannan EL, Isom OW, et al. A comparison of short- and long-term outcomes after off-pump and on-pump coronary artery bypass graft surgery with sternotomy. J Am Coll Cardiol 2004;43:557-564.
Brian J. deGuzman, M.D.
Mahesh H. Subramaniam, M.D.
Lahey Clinic Medical Center
Burlington, MA 01805
brian.j.deguzman@lahey.org
References
Khan NE, DeSouza A, Mister R, et al. A randomized comparison of off-pump and on-pump multivessel coronary-artery bypass surgery. N Engl J Med 2004;350:21-28.
Ochi M, Hatori N, Kanno S, Yamada K, Saji Y, Tanaka S. Coronary artery bypass grafting without cardiopulmonary bypass: a five-year experience. J Nippon Med Sch 2003;70:157-164.
Song HK, Petersen RJ, Sharoni E, Guyton RA, Puskas JD. Safe evolution towards routine off-pump coronary artery bypass: negotiating the learning curve. Eur J Cardiothorac Surg 2003;24:947-952.
Brown PP, Mack MJ, Simon AW, et al. Comparing clinical outcomes in high-volume and low-volume off-pump coronary bypass operation programs. Ann Thorac Surg 2001;72:S1009-S1015.
To the Editor: We congratulate Khan et al. for completing one of the few randomized studies comparing off-pump and on-pump coronary-artery bypass surgery. However, it is our opinion that to conclude that off-pump surgery is inferior to conventional bypass surgery on the basis of graft patency at three months in only 43 patients is premature and possibly misleading. The crux of any randomized surgical trial is the surgeons' equivalent proficiency with the techniques being evaluated. One could conclude that experience consisting of only 98 off-pump procedures, which require a different skill set, during the two years before the study (for an average of 25 procedures per surgeon per year) might bias the results against the off-pump cohort in terms of equivalent expertise. Additional factors that could have negatively affected patency in those who underwent off-pump surgery include the relatively low dose of intraoperative heparin, the absence of aggressive antiplatelet therapy with clopidogrel postoperatively, and the failure to use new suction devices to optimize exposure. Although this study is in contradistinction to the preponderance of those in the published literature, it does again highlight the need for a large, randomized trial with sufficient power to provide conclusive answers regarding off-pump coronary-artery bypass surgery.
Todd M. Dewey, M.D.
Mitchell J. Magee, M.D.
Michael J. Mack, M.D.
Cardiopulmonary Research Science and Technology Institute
Dallas, TX 75230
To the Editor: Khan et al. report a decrease of 10 percentage points in the rate of graft patency with off-pump as compared with on-pump coronary-artery bypass surgery. Most of the graft occlusions in the off-pump group occurred in the radial arteries, for which the rate of patency was only 76 percent. This finding is unexpected, since radial arteries have large luminal diameters and thick muscular walls, which facilitate the construction of anastomoses. A previous analysis of 523 radial-artery grafts performed off-pump revealed a 97.9 percent rate of early graft patency.1
Important determinants of radial-artery graft patency not discussed in the article include the severity of target-vessel stenosis (i.e., competitive flow), perioperative use of vasoconstrictors, and use of calcium-channel blockers.2,3 Recent studies have shown that graft occlusion is twice as likely when the radial artery is anastomosed to a target vessel with less than 70 percent stenosis.2,3 In the study by Khan et al., since the location of the target artery was not randomized, systematic differences in target-vessel selection may have influenced patency. The authors do not specify whether graft occlusion was due to focal stenosis or diffuse graft spasm. Concluding that radial-artery patency is poorer with off-pump surgery than with on-pump surgery on the basis of this study would be highly presumptuous.
Nimesh D. Desai, M.D.
Stephen E. Fremes, M.D.
Sunnybrook and Women's College Health Sciences Centre
Toronto, ON M4N 3M5, Canada
nimesh.desai@utoronto.ca
References
Kobayashi J, Tagusari O, Bando K, et al. Total arterial off-pump coronary revascularization with only internal thoracic artery and composite radial artery grafts. Heart Surg Forum 2002;6:30-37.
Desai ND, Cohen EA, Fremes SE. One year results of the Multi-center Radial Artery Patency Study. Circulation 2003;108:Suppl IV:IV-390. abstract.
Possati G, Gaudino M, Prati F, et al. Long-term results of the radial artery used for myocardial revascularization. Circulation 2003;108:1350-1354.
To the Editor: Khan et al. report that troponin T levels 6 and 12 hours after on-pump coronary surgery were higher than those after off-pump surgery. Early, transient elevation of the plasma troponin T level represents the release of cytosolic troponin T and does not necessarily reflect myocyte death. A substantial and unspecific elevation of the troponin T level occurs early after coronary surgery, even in patients who have no evidence of permanent myocardial injury.1 Myocardial necrosis leads to the breakdown of structurally bound troponin T and protracted elevation of the plasma troponin T level. The results recorded by Khan et al. at 72 hours provide a better estimate of permanent tissue loss than do the early recordings. These results suggest that there was a minor and similar degree of myocardial injury regardless of whether the procedure was performed on-pump or off-pump. Previous claims of lesser degrees of myocardial injury after off-pump surgery may not be justified. Do the authors think that the trade-off in inferior graft patency justifies off-pump coronary surgery in other than selected high-risk patients?
Rolf Svedjeholm, M.D., Ph.D.
Lars-G?ran Dahlin, M.D., Ph.D.
University Hospital Linkoping
SE-581 85 Linkoping, Sweden
rolf.svedjeholm@lio.se
References
Dahlin L-G, K?gedal B, Nylander E, Olin C, Rutberg H, Svedjeholm R. Unspecific elevation of plasma troponin-T and CK-MB after coronary surgery. Scand Cardiovasc J 2003;37:283-287.
The authors reply: Although we agree with deGuzman and Subramaniam, who suggest that there is a learning curve among surgeons performing off-pump coronary-artery bypass procedures, ours was a pilot randomized, controlled study. We suggest that inferior rates of patency may be the price to pay when off-pump surgery is introduced into a surgeon's practice, but that patency rates may improve with experience and the use of technological adjuncts. Such factors should influence our efforts to obtain informed consent from patients. Intracoronary shunts and blower misters were used in a minority of our graft procedures (43 of 333, or 13 percent), but apical suction devices were not available to us at the time.
The evaluation of a new surgical technique is controversial, but the randomized, controlled trial is the most robust test available. If the trial is performed too early, it can reasonably be argued that techniques have not matured and experience is limited; if it is performed too late and the period of surgical equipoise has expired, recruitment may be difficult on ethical grounds. This point is implicit in Dewey and colleagues' comments.
Desai and Fremes remark on the reduced rate of patency in our radial-artery grafts. Although we do not have data on target-vessel stenosis, we did not graft vessels with less than 70 percent stenosis. Our radial grafts were removed without the use of diathermy and stored for periods of up to 45 minutes in verapamil solution (2 mg per 100 ml of Ringer's solution), and all the patients received diltiazem at a dose of 60 to 90 mg twice daily from the day of surgery until six weeks postoperatively. Hirose et al.,1 who investigated the use of the gastroepiploic artery, reported three-year patency rates of 91.3 percent for the radial artery as compared with five-year rates of 97.0 percent for the left internal thoracic artery and 88.5 percent for the saphenous vein.
We appreciate the comments of Svedjeholm and Dahlin and believe that inferior graft patency may be justified in high-risk elderly patients to reduce the risk of stroke.2 Since our study was completed, Gaudino et al.3 have reported a significantly higher rate of recurrence of ischemia with off-pump surgery (recurrences in 71 of 184 patients ) than with on-pump surgery (recurrences in 19 of 103 patients , P<0.001). In a large audit of more than 68,000 patients in New York, Racz et al.4 showed that patients undergoing on-pump surgery had better long-term survival and greater freedom from revascularization than patients undergoing off-pump surgery. We would welcome a large randomized, controlled trial to test the long-term efficacy of off-pump surgery.
Natasha E. Khan, M.R.C.S.
Anthony C. DeSouza, F.R.C.S.
Royal Brompton and Harefield NHS Trust
London SW3 6NP, United Kingdom
John R. Pepper, M.Chir.
Imperial College of Science, Technology, and Medicine
London SW3 6LY, United Kingdom
References
Hirose H, Amano A, Takanashi S, Takahashi A. Coronary artery bypass grafting using the gastroepiploic artery in 1,000 patients. Ann Thorac Surg 2002;73:1371-1379.
Al-Ruzzeh S, Athanasiou T, George S, et al. Is the use of cardiopulmonary bypass for multivessel coronary artery bypass surgery an independent predictor of operative mortality in patients with ischemic left ventricular dysfunction? Ann Thorac Surg 2003;76:444-452.
Gaudino M, Glieca F, Alessandrini F, et al. High risk coronary artery bypass patient: incidence, surgical strategies, and results. Ann Thorac Surg 2004;77:574-580.
Racz MJ, Hannan EL, Isom OW, et al. A comparison of short- and long-term outcomes after off-pump and on-pump coronary artery bypass graft surgery with sternotomy. J Am Coll Cardiol 2004;43:557-564.