Off-pump vs. Conventional Coronary Artery Bypass Grafting: Early and One-Year Graft Patency, Cost, and Quality-of-Life Outcomes

Puskas JD, Williams WH, Mahoney EM, et al. J Am Med Assoc 2004; 291:1841-9 (with an accompanying editorial by Peterson ED, Mark DB. JAMA 2004; 291:1897-9)

Reviewer: KW Tim Park, MD
Beth Israel Deaconess Medical Center
Boston, MA

Background: In an effort to reduce morbidity associated with the use of cardiopulmonary bypass (CPB), off-pump coronary artery bypass (OP CAB) procedures have been developed and, in 2002, accounted for 21% of surgical coronary revascularization procedures in the US. Important challenges remain for the off-pump technique, including intraoperative hemodynamic instability during manipulation of the heart, technical difficulty with providing complete revascularization, particularly of the lateral and posterior walls, and the question of higher risks for anastomotic failures. Previous studies1-7 comparing OP CAB and conventional coronary artery bypass with CPB (CCAB) have been criticized for potential bias in patient selection and management and lack of generalization because of inclusion of low-risk patients only. The present study was designed to compare OP CAB and CCAB in unselected patients referred for elective primary, isolated CAB for in-hospital and one-year morbidity and mortality.

Methods: All patients referred for primary elective CAB at a university hospital were approached for inclusion in the study between March 2000 and August 2001, unless the patients were in cardiogenic shock requiring emergency surgery or preoperative intraaortic balloon pump. Of 297 patients asked to participate, 200 agreed. Three patients were withdrawn after enrollment because they required mitral valve surgery. All surgeries were performed by a single surgeon, who was skilled and experienced in OP CAB as well as CCAB. Graft patency was assessed by angiography at the time of discharge from the initial hospitalization and at one year follow-up, unless the patient had renal insufficiency or severe aortic atherosclerosis. Clinical outcome (adverse events, readmissions, and reinterventions) was assessed at 30 days and one year. Quality of life was measured using the EuroQol 6 and Medical Outcomes Short-Form Health Survey at four to six weeks, six months, and one year. Hospital cost estimates were based on Medicare cost formulations of resource-value units and conversion factors. The trial was 80% powered at a level of 0.05 to detect 5% difference in graft patency rates.

Results: Of 197 patients enrolled and not withdrawn from the study, four patients were crossed over, three from CCAB to OP CAB because of severe aortic atherosclerosis and one from OP CAB to CCAB because of need to graft a deeply intramyocardial coronary artery. Data analysis was by intention-to-treat. Patient demographic and comorbidity profiles were not significantly different from other similar trials. OP CAB and CCAB groups in the study were not significantly different, except that history of stroke was more common in the CCAB group (9.1% vs. 1.0%, P = 0.02) and Canadian Cardiovascular Society class III and IV were more common in the OP CAB group (24.5% vs. 12.1%, P = 0.03). The number of grafts was similar between the groups (3.2 per patient for OP CAB and 3.4 for CCAB).

Angiography was performed in 93.4% of the eligible patients at the time of hospital discharge and in 81% at one year follow-up. Overall early patency was similar between the groups (99.0% for OP CAB and 97.7% for CCAB, P = 0.22). Overall late patency at one year was also similar between the groups (93.6% for OP CAB and 95.8% for CCAB, P = 0.33). Early and late patency was similar between arterial conduits, venous conduits, and among grafts to each region of the heart. TIMI flows were similar as well. There were no significant between-group differences in any of the cardiovascular end points such as death, myocardial infarction, stroke, recurrent angina, readmission for cardiac events, or reinterventions. Quality of life measures were also similar, except that social functioning scores at one year tended to be better in the OP CAB group (P = 0.049). Hospitalization costs were substantially lower for the OP CAB group (a difference of $2,272, slightly more than 10% of the total cost). There were no additional cost savings in the OP CAB group after the initial hospitalization.

Discussion and Comments: In comparison to previous studies comparing OP CAB and CCAB, the present study is notable for not excluding high-risk patients, for performing a larger number of grafts for both groups, for comparing the two techniques on a broad array of in-hospital and one year outcome variables including quality of life and cost, and for the completeness of the follow-up including angiography in a high percent of the patients. Whereas the Prague-4 trial6 found a decrease in saphenous vein graft patency at one year for OP CAB (49% vs. 59% for CCAB) and Khan et al.7 found a decrease in arterial graft patency at three months for OP CAB (88% vs. 98% for CCAB, P = 0.002), the current found that there was no difference in graft patency, either venous or arterial, in any of the regions of the heart between OP CAB and CCAB. Rather than allowing one to conclude that OP CAB may be just as good as CCAB, what the current study demonstrates is that in the right hands and for the right patients, OP CAB can offer a safe, complete alternative to CCAB. Puskas, who performed all the surgeries of the current surgery, is known to be very skilled in OP CAB, routinely performing over 90% of his CAB's off pump.8 This may not be generalizable to other cardiac surgeons. There is a significant learning curve associated with OP CAB, affecting both completeness of revascularization and outcomes.8

Certainly what is needed is a large, multicenter (therefore, multi-surgeon) randomized trial comparing OP CAB and CCAB. As pointed out in the accompanying editorial by Peterson and Mark,8 such a trial would help decide whether the findings of the current study may be generalized to other surgical practices and be powered to detect any potential differences in outcome between the techniques either in the overall population or in certain subgroups. In fact, there is an on-going multicenter VA trial, which has enrolled 900 of the planned 2200 patients as of the date of the editorial.8 Though the study would have underrepresentaion of female patients, it would be expected to answer many of the questions regarding OP CAB vs. CCAB, at least, in male patients.

References

  1. Czerny M, Baumer H, Kilo J, et al. Complete revascularization in coronary artery bypass grafting with and without cardiopulmonary bypass. Ann Thorac Surg 2001; 71:165-9
  2. Van Dijk D, Nierich AP, Jansen EWL, et al. Early outcome after off-pump versus on-pump coronary bypass surgery: results from a randomized study. Circulation 2001; 104:1761-6
  3. Angelini GD, Taylor FC, Reeves BC, Ascione R. 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 randomized controlled trials. Lancet 2002; 359:1194-9
  4. Ascione R, Lloyd CT, Underwood MJ, et al. Economic implications of off-pump coronary artery bypass surgery: a prospective randomized study. Ann Thorac Surg 1999; 68:2237-42
  5. Nathoe HM, Van Dijk D, Jansen EWL, et al. A comparison of on-pump and off-pump coronary bypass surgery in low-risk patients. N Engl J Med 2003; 348:394-402
  6. Widimsky P, Stros P, Straka Z, Jirasek K. One-year coronary bypass graft patency: a randomized comparison between off-pump and on-pump surgery - angiographic results of the Prague-4 Trial. In: American College of Cardiology Annual Scientific Sessions: Late-Breaking Clinical Trials; March 7, 2004; New Orleans, LA
  7. Khan NE, 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; 350:21-8
  8. Peterson ED, Mark DB. Off-pump bypass surgery - ready for the big dance? J Am Med Assoc 2004; 291:1897-9
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