Correspondence
On-Pump versus Off-Pump CABG
N Engl J Med 2010; 362:851-854March 4, 2010
- Article
To the Editor:
In the Veterans Affairs Randomized On/Off Bypass (ROOBY) trial, Shroyer et al. (Nov. 5 issue)1 assigned 2203 patients to receive coronary-artery bypass grafting (CABG) either with the use of cardiopulmonary bypass (on-pump CABG) or without such bypass (off-pump CABG). The trial enrolled low-risk male patients in whom avoidance of cardiopulmonary bypass was unlikely to greatly improve the expected excellent outcomes.2 In a majority of patients, CABG was performed by surgical trainees under the supervision of attending surgeons who were remarkably inexperienced in the off-pump procedure and much more experienced in the on-pump procedure. The reported 12.4% rate of intraoperative conversion from planned off-pump CABG to on-pump CABG was five times the rate reported in the national database of the Society of Thoracic Surgeons3 and is an explicit indictment of the off-pump inexperience of surgeons, trainees, and anesthesia–nursing teams participating in the ROOBY trial.4 It is illogical to conduct a randomized trial comparing patient outcomes with alternative surgical techniques among surgical operators who have grossly asymmetric experience and expertise with the two procedures that are being compared. This is the “fatal flaw” of the ROOBY trial.
Off-pump CABG is a technically challenging surgical procedure that offers substantial benefit to patients at high risk for death and complications with on-pump CABG.3,5 It remains a very important tool for surgical coronary revascularization.
John D. Puskas, M.D.
Emory University, Atlanta, GA
john.puskas@emoryhealthcare. org Michael J. Mack, M.D.
Baylor Health Care System, Dallas, TXCraig R. Smith, M.D.
Columbia University Medical Center, New York, NYDr. Puskas reports receiving research and consulting fees from and serving on advisory boards for Medtronic and Maquet; Dr. Mack reports serving on an advisory board for Maquet.
No other potential conflict of interest relevant to this letter was reported.
5 References1
Shroyer AL ,Grover FL ,Hattler B , et al. On-pump versus off-pump coronary-artery bypass surgery. N Engl J Med 2009;361:1827-1837
Full Text | Web of Science | Medline2
Puskas JD ,Thourani VH ,Kilgo P , et al. Off-pump coronary artery bypass disproportionately benefits high-risk patients. Ann Thorac Surg 2009;88:1142-1147
CrossRef | Web of Science | Medline3
Puskas JD ,Edwards FH ,Pappas PA , et al. Off-pump techniques benefit men and women and narrow the disparity in mortality after coronary bypass grafting. Ann Thorac Surg 2007;84:1447-1456
CrossRef | Web of Science | Medline4
Edgerton JR ,Dewey TM ,Magee MJ , et al. Conversion in off-pump coronary artery bypass grafting: an analysis of predictors and outcomes. Ann Thorac Surg 2003;76:1138-1143
CrossRef | Web of Science | Medline5
Puskas JD ,Williams WH ,Mahoney EM , et al. Off-pump vs. conventional coronary artery bypass grafting: early and 1-year graft patency, cost, and quality-of-life outcomes: a randomized trial. JAMA 2004;291:1841-1849
CrossRef | Web of Science | Medline
To the Editor:
The findings of Shroyer et al. testify to the excellent contemporary results of CABG, whether on-pump or off-pump. However, even though the results largely reinforce the already well-established fact that there is no survival benefit to off-pump CABG in low-risk patients, this conclusion should not be generalized to higher-risk patients, for whom there is abundant evidence for superior outcomes with off-pump surgery.1 Furthermore, the inexperience of the surgeons with respect to this more demanding surgical technique was particularly notable, since the 53 participating surgeons enrolled on average only eight patients per year during a 5-year period and had unacceptably high conversion rates to on-pump surgery (12%) and incomplete revascularization (18%). It is likely that their inexperience contributed to other less favorable clinical outcomes as well. Similarly, the failure to combine off-pump CABG with greater use of arterial grafts2 and a “no-touch” aortic technique excludes the potential to minimize both overt and subclinical cerebral complications.3
David P. Taggart, M.D., Ph.D.
Oxford University, Oxford, United Kingdom
david.taggart@btinternet. com Dr. Taggart reports serving as an advisor to Medtronic.
No other potential conflict of interest relevant to this letter was reported.
3 References1
Abu-Omar Y ,Taggart DP . The present status of off-pump coronary artery bypass grafting. Eur J Cardiothorac Surg 2009;36:312-321
CrossRef | Web of Science | Medline2
Taggart DP ,D'Amico R ,Altman DG . Effect of arterial revascularisation on survival: a systematic review of studies comparing bilateral and single internal mammary arteries. Lancet 2001;358:870-875
CrossRef | Web of Science | Medline3
Abu-Omar Y ,Cader S ,Guerrieri Wolf L ,Pigott D ,Matthews PM ,Taggart DP . Short-term changes in cerebral activity in on-pump and off-pump cardiac surgery defined by functional magnetic resonance imaging and their relationship to microembolization. J Thorac Cardiovasc Surg 2006;132:1119-1125
CrossRef | Web of Science | Medline
To the Editor:
A randomized trial comparing two surgical techniques ought to include surgeons who are experienced in both procedures. Shroyer et al. conclude that patients who underwent off-pump CABG had worse composite outcomes and poorer graft patency at 1 year than did patients who underwent on-pump CABG. Disturbing was the assumption that performance of at least 20 off-pump CABG surgeries conferred “off-pump experience.” Although the prestudy off-pump experience averaged 120 cases, the median was only 50, indicating that some surgeons were quite experienced and the rest not so much. In 1313 of 2199 procedures (60%), a resident was the primary surgeon, with no difference in primary end points whether the resident or a staff member was the primary surgeon (perhaps because both were inexperienced?). A resident with possibly 100 cases under his or her belt faces a much steeper learning curve than a staff surgeon who has done several hundred. This study represents learning curves with respect to off-pump surgery for both residents and staff.
Teresa M. Kieser, M.D.
University of Calgary, Calgary, AL, Canada
t.kieserprieur@ucalgary. ca No potential conflict of interest relevant to this letter was reported.
To the Editor:
It is unclear whether the adverse outcomes that were associated with off-pump CABG might have been associated with exposure to aprotinin or endoscopic saphenous-vein harvesting. Both of these perioperative variables have a significant effect on outcome after CABG.1,2 This study raises important questions but should be interpreted in light of these possible confounders.
John G. Augoustides, M.D.
University of Pennsylvania, Philadelphia, PA
yiandoc@hotmail.com No potential conflict of interest relevant to this letter was reported.
2 References1
Mangano DT ,Tudor IC ,Dietzel C . The risk associated with aprotinin in cardiac surgery. N Engl J Med 2006;354:353-365
Full Text | Web of Science | Medline2
Lopes RD ,Hafley GE ,Allen KB , et al. Endoscopic versus open vein-graft harvesting in coronary-artery bypass surgery. N Engl J Med 2009;361:235-244
Full Text | Web of Science | Medline
To the Editor:
The major impetus to develop off-pump CABG surgery stemmed from the observation that atherosclerotic aortas are a major source of embolism when clamped during cardiac bypass.1 Atherosclerosis of the aorta is a major risk factor for the development of postoperative stroke and encephalopathy during on-pump CABG.2 Off-pump surgery was reported to have a lower risk of stroke than bypass with aortic clamping.2
The status of the aorta (either during preoperative testing or intraoperative observation) was not mentioned in the article by Shroyer et al. or in the accompanying editorial by Peterson.3 Knowledge of the presence, location, and severity of aortic disease — as well as the cardiac ejection fraction and the extent of coronary artery disease and lesions in neck and cranial arteries that supply the brain — would allow surgeons to selectively choose on-pump versus off-pump surgery, yet such detailed preoperative analysis is not routinely performed.4
The idea that one surgical strategy fits all is faulty. Much more sensible would be to evaluate patients as thoroughly as possible before surgery and then choose the most appropriate technique for that patient.4
Louis R. Caplan, M.D.
Beth Israel Deaconess Medical Center, Boston, MA
lcaplan@bidmc.harvard. edu No potential conflict of interest relevant to this letter was reported.
4 References1
Barbut D ,Caplan LR . Brain complications of cardiac surgery. Curr Probl Cardiol 1997;22:449-480
CrossRef | Medline2
Bucerius J ,Gummert JF ,Borger MA , et al. Stroke after cardiac surgery: a risk factor analysis of 16,184 consecutive adult patients. Ann Thorac Surg 2003;75:472-478
CrossRef | Web of Science | Medline3
Peterson ED . Innovation and comparative-effectiveness research in cardiac surgery. N Engl J Med 2009;361:1897-1899
Full Text | Web of Science | Medline4
Caplan LR . Translating what is known about neurological complications of coronary artery bypass graft surgery into action. Arch Neurol 2009;66:1062-1064
CrossRef | Web of Science | Medline
Author/Editor Response
The ROOBY trial showed better 1-year outcomes and graft patency among patients undergoing on-pump CABG than among those undergoing off-pump CABG. The correspondents raise important questions regarding the effect of surgeons' experience, the use of residents as primary surgeons, and conversions of surgical procedure on the trial's primary outcomes. Similar to previous trials, our study showed no difference in primary short-term or 1-year composite outcomes, regardless of the participating surgeon's experience (>50 or >100 previous off-pump cases) or whether the attending or a trainee was the primary surgeon (for details, see Table 1 in the Supplementary Appendix, available with the full text of this letter at NEJM.org).1-4 These findings remained consistent in both the intention-to-treat analysis and after the exclusion of surgical conversions.
Regarding Taggart's question about our study's generalizability to subgroups of high-risk patients: we enrolled many patients with high-risk coexisting conditions. Among these subgroups, there was no difference in the 1-year composite end point between the two study groups. Worse short-term outcomes were seen among patients with diabetes who underwent the off-pump technique (P=0.01); this difference did not persist after removal of patients who underwent surgical conversions (P=0.10) (Table 1 in the Supplementary Appendix).
With respect to the comments of Augoustides regarding the use of aprotinin and endoscopic vein harvesting for saphenous-vein grafts: we agree that these processes of care may affect outcomes. Aprotinin was used in 6.0% of patients (4.3% of those who were not converted) in the off-pump group versus 28.6% (29.9% of those who were not converted) in the on-pump group. Further analysis of this aprotinin imbalance on the study's results appears warranted. Fifteen months after the initiation of our trial, data capture for endoscopic vein harvesting was initiated. For this period, the proportions of episodes of endoscopic vein harvesting were balanced between the two study groups (P=1.0) and therefore should not have an effect on the study's conclusions.
Regarding Caplan's comments: our study was designed to assess the use of off-pump versus on-pump CABG, not other approaches, such as total arterial revascularization and aortic “no-touch” techniques. Our clinician team concurs that in some patients who undergo CABG, an aortic no-touch approach may be beneficial. In our study, there were 40 conversions of on-pump procedures to off-pump procedures (3.6%). Of these, 23 were due to surgeons' concerns related to calcification of the ascending aorta. It is important to note that there were no differences in overall neurocognitive outcomes between the two study groups.
In summary, these sensitivity analyses verify that our findings remain relevant to the majority of men at low-to-moderate risk of death at 30 days and perioperative complications, as well as to most cardiac surgical groups. For women, high-risk men, and other intraoperative surgical techniques, future research will be required to build an evidence base to optimally select patients for off-pump procedures.
A. Laurie W. Shroyer, Ph.D., M.S.H.A.
Northport Veterans Affairs Medical Center, Northport, NY
annie.shroyer@va. gov Dimitri Novitzky, M.D., Ph.D.
James A. Haley Veterans Hospital, Tampa, FLFrederick L. Grover, M.D.
Veterans Affairs Eastern Colorado Health Care System, Denver, COfor the Veterans Affairs ROOBY Study Group
Since publication of their article, the authors report no further potential conflict of interest.
4 References1
Caputo M ,Reeves BC ,Rogers CA ,Ascione R ,Angelini GD . Monitoring the performance of residents during training in off-pump coronary surgery. J Thorac Cardiovasc Surg 2004;128:907-915
CrossRef | Web of Science | Medline2
Karamanoukian HL ,Panos AL ,Bergsland J ,Salerno TA . Perspectives of a cardiac surgery resident in-training on off-pump coronary bypass operation. Ann Thorac Surg 2000;69:42-45
CrossRef | Web of Science | Medline3
Ascione R ,Reeves BC ,Pano M ,Angelini GD . Trainees operating on high-risk patients without cardiopulmonary bypass: a high-risk strategy? Ann Thorac Surg 2004;78:26-33
CrossRef | Web of Science | Medline4
Feng ZZ ,Shi J ,Zhao XW ,Xu ZF . Meta-analysis of on-pump and off-pump coronary arterial revascularization. Ann Thorac Surg 2009;87:757-765
CrossRef | Web of Science | Medline
Author/Editor Response
I agree with Caplan's comments that aortic atherosclerosis is a risk factor for stroke after bypass surgery. In my editorial, I suggest that “future subgroup analyses are needed to determine whether there were specific high-risk subpopulations for which the off-pump technique was particularly beneficial.” Therefore, if Shroyer et al. have data regarding the extent of aortic calcification in study patients, then they should examine whether treatment outcomes varied as a function of this risk factor. Finally, I do not believe that my editorial supports a “one surgical strategy fits all” bottom line. Although the ROOBY trial did not support a general replacement of off-pump surgery with on-pump surgery, I conclude that off-pump surgery may be “a technique reserved for selected patients and skilled surgeon advocates.”
Eric D. Peterson, M.D., M.P.H.
Duke University Medical Center, Durham, NCSince publication of his article, the author reports no further potential conflict of interest.
- Citing Articles (4)
Citing Articles
1
Damien J. LaPar, Carlos M. Mery, Benjamin D. Kozower, John A. Kern, Irving L. Kron, George J. Stukenborg, Gorav Ailawadi. (2012) The effect of surgeon volume on mortality for off-pump coronary artery bypass grafting. The Journal of Thoracic and Cardiovascular Surgery
CrossRef2
Dimitri Novitzky, Janet H. Baltz, Brack Hattler, Joseph F. Collins, Elizabeth Kozora, A. Laurie Shroyer, Frederick L. Grover. (2011) Outcomes After Conversion in the Veterans Affairs Randomized On Versus Off Bypass Trial. The Annals of Thoracic Surgery 92:6, 2147-2154
CrossRef3
J. James Edelman, Tristan D. Yan, Ratnasari Padang, Paul G. Bannon, Michael P. Vallely. (2010) Off-Pump Coronary Artery Bypass Surgery Versus Percutaneous Coronary Intervention: A Meta-Analysis of Randomized and Nonrandomized Studies. The Annals of Thoracic Surgery 90:4, 1384-1390
CrossRef4
Masaru Nishimi, Tadashi Tashiro. (2010) Off-Pump Coronary Artery Bypass vs Percutaneous Coronary Intervention. Circulation Journal 74:12, 2750-2757
CrossRef
