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J Thorac Cardiovasc Surg 2007;133:e2-e3
© 2007 The American Association for Thoracic Surgery

Brief Communication

Off-pump coronary artery bypass sacrifices graft patency: Meta-analysis of randomized trials

Department of Cardiovascular Surgery, Shizuoka Medical Center, Shizuoka, Japan.

Received for publication August 10, 2006; accepted for publication August 25, 2006.

^_* Address for reprints: Hisato Takagi, MD, PhD, Department of Cardiovascular Surgery, Shizuoka Medical Center, 762-1 Nagasawa, Shimizu-cho, Sunto-gun, Shizuoka 411-8611, Japan. (Email: kfgth973{at}ybb.ne.jp).

The most recent meta-analysis¹ of 37 randomized trials of off-pump coronary artery bypass (OPCAB) versus conventional coronary artery bypass grafting (CABG) demonstrated that mortality, stroke, myocardial infarction, and renal failure were not reduced in OPCAB; however, selected short-term and midterm clinical and resource outcomes were improved compared with CABG. The previous cumulative analysis (by Parolari and associates²) of 5 prospective randomized studies (by Nathoe,³ Khan,⁴ Puskas,⁵ Widimsky,⁶ Lingaas,⁷ and their associates) then available in the literature, however, documented a reduction in postoperative patency of bypass grafts performed during OPCAB procedures. Since the meta-analysis by Parolari and associates² was conducted, Lingaas and colleagues⁸ have updated the 3-month patency,⁷ and Kobayashi and coworkers⁹ and Al-Ruzzeh and associates¹⁰ have reported results of other randomized controlled trials. In these trials,^8-10 OPCAB provided the same angiographic graft patency as CABG, despite the conclusion of the meta-analysis by Parolari and colleagues.² To reassess differences in graft patency between OPCAB and CABG, we performed a meta-analysis of currently available randomized controlled trials of OPCAB versus CABG.

Materials and Methods

All prospective randomized controlled trials that compared patency at least 3 months after OPCAB and CABG were identified using a 2-level search strategy. First, a public domain database (MEDLINE) was searched with a Web-based search engine (PubMed). Second, relevant studies were identified through a manual search of secondary sources including references of initially identified articles. The MEDLINE database was searched from January 1966 to June 2006. Keywords included "off-pump," "off pump," "opcab," "patency," and "randomized controlled trial." Studies considered for inclusion met the following criteria: The design was a prospective randomized controlled clinical trial; patients were randomly assigned to OPCAB versus CABG; and main outcomes included at least 3-month graft patency evaluated by angiography. All qualifying studies were assessed for adequate blinding of randomization, completeness of follow-up, and objectivity of the outcome assessment. Data regarding arterial graft and venous graft (excluding radial artery graft as available) patency were abstracted from each individual study. For each study, data regarding patency in both the OPCAB and CABG groups were used to generate risk ratios (RRs) (<1, favors OPCAB; >1, favors CABG) and risk differences (RDs) (<0, favors OPCAB; >0, favors CABG) for graft "occlusion" and 95% confidence intervals (CIs). Study-specific estimates were combined with a random-effect model. Between-study heterogeneity was analyzed by standard ² tests. Sensitivity analyses were performed to assess the contribution of each study to the pooled estimate by excluding individual trials one at a time and recalculating the pooled RR and RD estimates for the remaining studies. Publication bias was assessed graphically with a funnel plot and mathematically with an adjusted rank-correlation test.

Results

Our search identified 6 prospective randomized controlled clinical trials^3-6,8,10 (Table 1). We excluded the trial by Kobayashi and associates⁹ because these workers merely examined early (within 3 weeks after the operation) graft patency. Allocation concealment and blinding were not possible in these trials given that the intervention was surgical; however, all trials used a blinded committee for adjudication of events. Careful accounting for dropouts and crossovers was provided in all cases, and all but one analysis⁵ were conducted by intention-to-treat. All of the 6 individual trials demonstrated a statistically nonsignificant benefit of CABG over OPCAB for overall graft patency. Pooled analysis demonstrated a statistically significant 27% increase in overall graft "occlusion" with OPCAB relative to CABG (RR, 1.27; 95% CI, 1.03-1.56; P = .0234) (RD, 3.0%; 95% CI, 0.6%-5.4%; P = .0129). There was neither trial heterogeneity of results nor evidence of significant publication bias. Exclusion of any single trial from the analysis did not substantively alter the overall result of our analysis. Subanalyses demonstrated a statistically nonsignificant benefit of CABG over OPCAB for arterial graft patency (RR, 1.17; 95% CI, 0.62-2.24; P = .6259) (RD, 2.0%; 95% CI, –1.2%-5.2%; P = .2195) and a statistically significant 28% increase in venous graft "occlusion" with OPCAB relative to CABG (RR, 1.28; 95% CI, 1.06-1.54; P = .0094) (RD, 4.0%; 95% CI, 0.2%-7.8%; P = .0396).

The present meta-analysis demonstrated a significant increase in overall graft "occlusion," especially in venous graft "occlusion," with OPCAB relative to CABG. On the one hand, OPCAB decreases arterial fibrillation, transfusion, inotrope requirements, respiratory infections, ventilation time, intensive care unit stay, and hospital stay.¹ At the expense of graft patency, dare we perform OPCAB rather than CABG to merely improve these selected clinical and resource outcomes?

See related editorial on page 1.

 

References

1. Cheng DC, Bainbridge D, Martin JE, Novick RJ, Evidence-Based Perioperative Clinical Outcomes Research Group Does off-pump coronary artery bypass reduce mortality, morbidity, and resource utilization when compared with conventional coronary artery bypass?. A meta-analysis of randomized trials. Anesthesiology 2005;102:188-203.[Medline]
   
2. Parolari A, Alamanni F, Polvani G, Agrifoglio M, Chen YB, Kassem S, et al. Meta-analysis of randomized trials comparing off-pump with on-pump coronary artery bypass graft patency. Ann Thorac Surg 2005;80:2121-2125.[Abstract/Free Full Text]
   
3. Nathoe HM, van Dijk D, Jansen EW, Suyker WJ, Diephuis JC, van Boven WJ, 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.[Abstract/Free Full Text]
   
4. Khan NE, De Souza A, Mister R, Flather M, Clague J, Davies S, et al. A randomized comparison of off-pump and on-pump multivessel coronary-artery bypass surgery. N Engl J Med 2004;350:21-28.[Abstract/Free Full Text]
   
5. Puskas JD, Williams WH, Mahoney EM, Huber PR, Block PC, Duke PG, 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.[Abstract/Free Full Text]
   
6. Widimsky P, Straka Z, Stros P, Jirasek K, Dvorak J, Votava J, et al. One-year coronary bypass graft patency: a randomized comparison between off-pump and on-pump surgery—angiographic results of the PRAGUE-4 trial. Circulation 2004;110:3418-3423.[Abstract/Free Full Text]
   
7. Lingaas PS, Hol PK, Lundblad R, Rein KA, Tonnesen TI, Svennevig JL, et al. Clinical and angiographic outcome of coronary surgery with and without cardiopulmonary bypass: a prospective randomized trial. Heart Surg Forum 2004;7:37-41.[Medline]
   
8. Lingaas PS, Hol PK, Lundblad R, Rein KA, Mathisen L, Smith H-J, et al. Clinical and radiologic outcome of off-pump coronary surgery at 12 months follow-up: a prospective randomized trial. Ann Thorac Surg 2006;81:2089-2096.[Abstract/Free Full Text]
   
9. Kobayashi J, Tashiro T, Ochi M, Yaku H, Watanabe G, Satoh T, et al. Early outcome of a randomized comparison of off-pump and on-pump multiple arterial coronary revascularization. Circulation 2005;112(9 Suppl):I338-I343.[Medline]
   
10. Al-Ruzzeh S, George S, Bustami M, Wray J, Ilsley C, Athanasiou T, et al. Effect of off-pump coronary artery bypass surgery on clinical, angiographic, neurocognitive, and quality of life outcomes: randomised controlled trial. BMJ 2006;332:1365.[Abstract/Free Full Text]
    

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