OPCAB surgery: time for a reappraisal?

Abstract

CARDIOPULMONARY BYPASS is arguably one of the most important medical innovations of the last century.1Mangano C.M Hill L Cartwright C.R et al.Cardiopulmonary Bypass for the Anesthesiologist.in: Kaplan J.A Reich D.L Konstadt S.N Cardiac Anaesthesia. (ed 4). WB Saunders, Philadelphia1999: 1061-1111Google Scholar Without it, modern cardiac surgery would not have been able to develop into the specialty it is today, and countless thousands of patients would have been denied its benefits. However, cardiopulmonary bypass is not free from adverse effects, and, given the nature and magnitude of the intervention, it is perhaps remarkable how well these have been contained. Nonetheless, the complications of its use are real and at times can be devastating. Contact activation, resulting in numerous inflammatory processes and maldistribution of blood flow, particularly when associated with an enhanced embolic load, are important causes of morbidity. The damage these processes may inflict on vital organs is most marked when there is evidence of preexisting organ dysfunction, and this will be most apparent in the elderly and the very sick. The common experience of cardiac centers today is that these patients form an ever-increasing proportion of the caseload.2Docherty A Taylor J Brady A.J.B The future of cardiology—Heart disease in older patients.Br J Cardiol. 2003; 10: 45-48Google Scholar It is therefore not surprising that the use of techniques of coronary revascularization without cardiopulmonary bypass has increased. The lion’s share has been taken up by interventional cardiology with percutaneous transluminal coronary angioplasty and intraluminal coronary stenting; and the use of drug-eluting stents will further this trend.3Moses J.W Leon M.B Popma J.J et al.Sirolimus-eluting stents versus standard stents in patients with stenosis in a native coronary artery.New Eng J Med. 2003; 349: 1315-1323Crossref PubMed Scopus (4051) Google Scholar, 4Arjomand H Turi Z.G McCormick D et al.Percutaneous coronary intervention Historical perspectives, current status, and future directions.Am Heart J. 2003; 146: 787-796Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar In surgical revascularization, there has been growing interest in coronary revascularization without cardiopulmonary bypass support (off-pump coronary artery bypass [OPCAB]. The use of tissue stabilization devices has eased surgical access to the circumflex and distal right coronary arteries,5Scott N.A Knight J.L Bidstrup B.P et al.Systematic review of beating heart surgery with the Octopus Tissue Stabilizer.Eur J Cardiothorac Surg. 2002; 21: 804-817Crossref PubMed Scopus (22) Google Scholar, 6Kasahara K Kamata S Experience of off-pump coronary artery bypass grafting with Starfish heart positioner.Kyobu Geka. 2003; 56: 385-388PubMed Google Scholar and many patients can now can be offered the same operation on or off pump. The published results appeared to vary from promising to excellent, and those clinicians given to predicting the future were confident in the assertion that the proportion of surgical revascularization off pump would increase in the forthcoming decade.7Feneck R.O Cardiac anaesthesia The last 10 years.Anaesthesia. 2003; 58: 1171-1177Crossref PubMed Scopus (4) Google Scholar However, a small study by Khan et al,8Khan N.E De Souza 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: 21-28Crossref PubMed Scopus (483) Google Scholar published in the New England Journal of Medicine, may have undermined this confidence. While finding many similar outcomes to current published studies, they differed in one important respect. Coronary angiography at 3 months showed a reduction in graft patency in the OPCAB group compared with those patients revascularized on pump (88% v 98%). Does this finding represent a small setback on the inexorable road to OPCAB revascularization or is it time for a fundamental reappraisal? So far, the evidence in favor of OPCAB is impressive. Numerous recent studies have shown that OPCAB is associated with comparable early survival, less organ damage, a lower incidence of reoperation for bleeding, less blood and blood product usage, a reduced inflammatory response, shortened intensive care unit stay, and shortened hospital stay.9Puskas J.D Williams W.H Duke P.G et al.Off-pump coronary artery bypass grafting provides complete revascularization with reduced myocardial injury, transfusion requirements, and length of stay A prospective randomized comparison of two hundred unselected patients undergoing off-pump versus conventional coronary artery bypass grafting.J Thorac Cardiovasc Surg. 2003; 125: 797-808Abstract Full Text Full Text PDF PubMed Scopus (502) Google Scholar, 10Sharony R Bizekis C.S Kanchuger M et al.Off-pump coronary artery bypass grafting reduces mortality and stroke in patients with atheromatous aortas A case control study.Circulation. 2003; 108: II15-II20PubMed Google Scholar, 11Al-Ruzzeh S Ambler G Asimakopoulos G et al.Off-pump coronary artery bypass (OPCAB) surgery reduces risk-stratified morbidity and mortality A United Kingdom multi-center comparative analysis of early clinical outcome.Circulation. 2003; 108: II1-II8PubMed Google Scholar, 12Meharwal Z.S Mishra Y.K Kohli V et al.Multivessel off-pump coronary artery bypass analysis of 4953 cases.Heart Surg Forum. 2003; 6: 153-159PubMed Google Scholar, 13Boening A Friedrich C Hedderich J et al.Early and medium-term results after on-pump and off-pump coronary artery surgery A propensity score analysis.Ann Thorac Surg. 2003; 76: 2000-2006Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 14Muneretto C Bisleri G Negri A et al.Off-pump coronary artery bypass surgery technique for total arterial myocardial revascularization A prospective randomized study.Ann Thorac Surg. 2003; 76: 778-782Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar, 15Lev-Ran O Loberman D Matsa M et al.Reduced strokes in the elderly The benefits of untouched aorta off-pump coronary surgery.Ann Thorac Surg. 2004; 77: 102-107Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar, 16Kathiresan S MacGillivray T.E Lewandrowski K et al.Off-pump coronary bypass grafting is associated with less myocardial injury than coronary bypass surgery with cardiopulmonary bypass.Heart Surg Forum. 2003; 6: E174-E178PubMed Google Scholar, 17Nuttall G.A Erchul D.T Haight T.J et al.A comparison of bleeding and transfusion in patients who undergo coronary artery bypass grafting via sternotomy with and without cardiopulmonary bypass.J Cardiothorac Vasc Anesth. 2003; 17: 447-451Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar, 18Al-Ruzzeh S Hoare G Marczin N et al.Off-pump coronary artery bypass surgery is associated with reduced neutrophil activation as measured by the expression of CD11b A prospective randomized study.Heart Surg Forum. 2003; 6: 94-98PubMed Google Scholar, 19Parolari A Alamanni F Cannata A et al.Off-pump versus on-pump coronary artery bypass Meta-analysis of currently available randomized trials.Ann Thorac Surg. 2003; 76: 37-40Abstract Full Text Full Text PDF PubMed Scopus (122) Google Scholar, 20Lee J.D Lee S.J Tsushima W.T et al.Benefits of off-pump bypass on neurologic and clinical morbidity A prospective randomized trial.Ann Thorac Surg. 2003; 76: 18-25Abstract Full Text Full Text PDF PubMed Scopus (178) Google Scholar, 21Deuse T Detter C Samuel V et al.Early and midterm results after coronary artery bypass grafting with and without cardiopulmonary bypass Which patient population benefits the most?.Heart Surg Forum. 2003; 6: 77-83PubMed Google Scholar, 22Novick R.J Fox S.A Stitt L.W et al.Effect of off-pump coronary artery bypass grafting on risk-adjusted and cumulative sum failure outcomes after coronary artery surgery.J Card Surg. 2002; 17: 520-528Crossref PubMed Scopus (22) Google Scholar, 23Al-Ruzzeh S Nakamura K Athanasiou T et al.Does off-pump coronary artery bypass (OPCAB) surgery improve the outcome in high-risk patients? A comparative study of 1398 high-risk patients.Eur J Cardiothorac Surg. 2003; 23: 50-55Crossref PubMed Scopus (172) Google Scholar, 24Angelini G.D Taylor F.C Reeves B.C et al.Early and midterm outcome after off-pump and on-pump surgery in Beating Heart Against Cardioplegic Arrest Studies (BHACAS 1 and 2) A pooled analysis of two randomised controlled trials.Lancet. 2002; 359: 1194-1199Abstract Full Text Full Text PDF PubMed Scopus (505) Google Scholar, 25Al-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: 444-451Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar Although early studies generally reported a smaller number of grafts in the OPCAB groups, particularly a lower number of grafts to the circumflex coronary artery, more recent experience suggests the extent of revascularization is comparable to conventional CABG. However, fewer studies have performed repeat angiography. Calafiore et al26Calafiore A.M Teodori G Di Giammarco G et al.Multiple arterial conduits without cardiopulmonary bypass Early angiographic results.Ann Thorac Surg. 1999; 67: 450-456Abstract Full Text Full Text PDF PubMed Scopus (130) Google Scholar performed early repeat angiography after OPCAB and reported graft patency rates of over 95%. Puskas et al27Puskas J.D Thourani V.H Marshall J.J et al.Clinical outcomes, angiographic patency, and resource utilization in 200 consecutive off-pump coronary bypass patients.Ann Thorac Surg. 2001; 71: 1477-1484Abstract Full Text Full Text PDF PubMed Scopus (193) Google Scholar, 28Puskas J.D Williams W.H Mahoney E.M et al.Off-pump vs conventional coronary artery bypass grafting Early and 1 year graft patency, cost, and quality-of-life outcomes.JAMA. 2004; 291: 1841-1849Crossref PubMed Scopus (481) Google Scholar have reported similarly high graft patency rates after early angiography in OPCAB patients. Nathoe et al29Nathoe H.M van Dijk D Jansen E.W.L et al.A comparison of on-pump and off-pump coronary artery bypass surgery in low-risk patients.N Engl J Med. 2003; 348: 394-402Crossref PubMed Scopus (385) Google Scholar restudied patients at 1 year with comparable angiographic results, but their study was confined to low-risk patients and only 64% of the patients agreed to repeat angiography. In a meta-analysis of earlier trials with repeat angiography, Mack et al30Mack M.J Osborne J.A Shennib H Arterial graft patency in coronary artery bypass grafting What do we really know?.Ann Thorac Surg. 1998; 66: 1055-1059Abstract Full Text Full Text PDF PubMed Scopus (100) Google Scholar found that on- and off-pump graft patency rates were generally similar, but these studies were confined to angiography of the left internal mammary artery anastomosed to the left anterior descending coronary artery. Recent studies of OPCAB surgery from the United Kingdom have tended to be in agreement with those from elsewhere in reporting good results and a reduction in operative complications.11Al-Ruzzeh S Ambler G Asimakopoulos G et al.Off-pump coronary artery bypass (OPCAB) surgery reduces risk-stratified morbidity and mortality A United Kingdom multi-center comparative analysis of early clinical outcome.Circulation. 2003; 108: II1-II8PubMed Google Scholar, 18Al-Ruzzeh S Hoare G Marczin N et al.Off-pump coronary artery bypass surgery is associated with reduced neutrophil activation as measured by the expression of CD11b A prospective randomized study.Heart Surg Forum. 2003; 6: 94-98PubMed Google Scholar, 23Al-Ruzzeh S Nakamura K Athanasiou T et al.Does off-pump coronary artery bypass (OPCAB) surgery improve the outcome in high-risk patients? A comparative study of 1398 high-risk patients.Eur J Cardiothorac Surg. 2003; 23: 50-55Crossref PubMed Scopus (172) Google Scholar, 24Angelini G.D Taylor F.C Reeves B.C et al.Early and midterm outcome after off-pump and on-pump surgery in Beating Heart Against Cardioplegic Arrest Studies (BHACAS 1 and 2) A pooled analysis of two randomised controlled trials.Lancet. 2002; 359: 1194-1199Abstract Full Text Full Text PDF PubMed Scopus (505) Google Scholar, 25Al-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: 444-451Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar Indeed, the 2 surgeons in the Khan et al study have been coauthors on a previous study reporting favorably on OPCAB surgery.25Al-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: 444-451Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar So what therefore could account for Khan et al’s apparently poor results? Regarding the anesthesia, although the details of the technique are lacking in the publication, the isoflurane-based opioid-supplemented technique used in both groups would be recognizable in any major center as a standard technique. Epidural techniques were not used in the study. The importance of high-quality anesthesia for OPCAB is generally well recognized,31Shanewise J.S Ramsay J.G Off-pump coronary surgery How do the anesthetic considerations differ?.Anesthesiol Clin North Am. 2003; 21: 613-623Abstract Full Text Full Text PDF PubMed Scopus (6) Google Scholar and another group from the Royal Brompton has published on this topic.32Al-Ruzzeh S Amrani M Boscoe M et al.Integrated approach to off-pump coronary artery bypass surgery.Cardiovasc Surg. 2003; 11: 299-303Crossref PubMed Scopus (4) Google Scholar There are currently both interest and concern about the coagulation management of patients undergoing OPCAB. Cardiopulmonary bypass may serve to initiate a coagulopathy, which may protect patients against early thrombosis and graft occlusion. Platelet function after OPCAB has been shown to be improved (ie, more likely to produce clot formation) compared with conventional CABG,33Moller C.H Steinbruchel D.A Platelet function after coronary artery bypass grafting Is there a procoagulant activity after off-pump compared with on-pump surgery?.Scand Cardiovasc J. 2003; 37: 149-153Crossref PubMed Scopus (44) Google Scholar, 34Bidstrup B.P Scarrott H Luque M Platelet function after off- pump coronary surgery.Heart Surg Forum. 2003; 6: 286-287PubMed Google Scholar and a hypercoagulable state has been noted after OPCAB.35Quigley R.L Fried D.W Pym J et al.Off-pump coronary artery bypass surgery may produce a hypercoagulable patient.Heart Surg Forum. 2003; 6: 94-98PubMed Google Scholar None of the patients in the Khan et al study received aprotinin or tranexamic acid, and both groups were treated conventionally with aspirin at 6 hours after revascularization. However, the patients undergoing OPCAB received a reduced dose of heparin. There is speculation concerning the need for a full dose of heparin for OPCAB surgery or, alternatively, active coagulation management using regular testing.36Baykut D Weichelt K Wehrle J et al.The value of heparin concentration monitoring in off-pump coronary bypass surgery.Eur J Med Res. 2003; 8: 161-164PubMed Google Scholar It could be argued that any adverse effects of a hypercoagulable state would manifest themselves very early, and because the Khan et al study patients’ follow-up angiography at 3 months was the only postoperative angiography performed, in theory any problems with the anastomoses could have been present from the early postoperative period. The technique of quantitative angiography is well described and is clearly valuable in detecting incomplete graft occlusion.37Diegeler A Thiele H Falk V et al.Comparison of stenting with minimally invasive bypass surgery for stenosis of the left anterior descending coronary artery.N Engl J Med. 2002; 347: 561-566Crossref PubMed Scopus (192) Google Scholar It is known from previous studies that early stenosis and/or poor vessel caliber are among the factors that may predict graft failure in CABG patients, and the same may be true in OPCAB. For many readers, the most important issue will relate to those surgical factors that are known to affect the quality of the anastomoses. The time taken for each anastomosis in the Khan et al study appears unremarkable. The OPCAB anastomoses took longer (13.1 v 9.5 minutes), but not so long as to suggest difficulty or unfamiliarity with the technique. The conversion rate of less than 4% (2/54) is unremarkable given the small size of the study. The OPCAB group had significantly fewer grafts planned and a significantly greater number of radial artery grafts used, and, interestingly, it was these radial artery grafts that were most likely to be occluded at angiography. The clinical course of the patients after revascularization and into the early postoperative period was comparable and unremarkable in both groups. In a study such as this, questions about the experience of the surgical team and the impact this may have on the quality of the anastomoses will be asked, and the authors are honest enough to do this themselves. The angiographic results of their on-pump anastomoses were excellent, so they are clearly competent at CABG. However, they freely admit that they do not do the majority, or even a large minority of their coronary revascularizations off pump, and that perhaps there is a much longer learning curve to the OPCAB procedure than they previously thought. Nonetheless, the same institution has recently published data suggesting that OPCAB can be taught to cardiac surgical trainees with good results, although very few patients in this study consented to repeat angiography.38Jenkins D Al-Ruzzeh S Khan S et al.Multivessel off-pump coronary artery bypass grafting can be taught to trainee surgeons.J Card Surg. 2003; 18: 419-424Crossref PubMed Scopus (11) Google Scholar It will always be difficult to assess the quality of anastomosis objectively during surgery, but Bonatti et al39Bonatti J Danzmayr M Schachner T Intraoperative angiography for quality control in MIDCAB and OPCAB.Eur J Cardiothorac Surg. 2003; 24: 647-649Crossref PubMed Scopus (14) Google Scholar have reported a small series of patients in whom coronary angiography was performed on the operating table immediately after minimally invasive direct coronary artery bypass and OPCAB. They found that 10% of grafts needed major revision. The other patient outcomes and clinical results in the Khan et al study were comparable to those recently published elsewhere, and it is therefore tempting to speculate whether this combination of apparently good clinical outcomes but with suboptimal quality of anastomoses is a problem that is more widespread. If so, there may be significant trouble for the future. Many of the earlier studies of OPCAB concluded that further detailed follow-up is required, and it is to be hoped that this will indeed be undertaken. Perhaps detailed follow-up of graft patency will become easier when routine noninvasive coronary imaging becomes more available. So, should Khan et al’s findings be dismissed, concluding that the study was too small, the surgeons too inexperienced, the angiographic assessment too detailed, and the coagulation management open to criticism? Although OPCAB procedures can be done with relative ease and good clinical outcomes, there is very little direct evidence on the quality of the anastomoses and less about the longer-term effects. More data in these areas would be very welcome indeed, and clinicians will await the large randomized trial by the U.S. Department of Veterans Affairs with 2200 patients over 4 years. The randomized controlled trial is the essence of scientific clinical investigation, but there comes a point when the clinician needs to consider the individual patient. For some patients, the avoidance of cardiopulmonary bypass may be so important that a lesser quality of revascularization may be tolerated. For others, the impact of bypass may be relatively trivial compared with the benefit of improved surgical access for a difficult anastomosis to an important vessel. Matching the operation to the individual patient is fundamental to surgical care,40MacGillivray T.E Vlahakes G.J Patency and the pump-the risks and benefits of off-pump CABG.N Engl J Med. 2004; 350: 3-4Crossref PubMed Scopus (25) Google Scholar and anesthesiologists and surgeons need to become proficient in both on- and off-pump techniques. The Khan et al study should make clinicians pause in their enthusiasm simply to consider which procedure, on- or off-pump, is in the individual patient’s best interests.