To pump, or not to pump, that is the question

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CTSNet classification: 23.1

To the Editor:

We read with great interest the article by Kuss and associates,¹ who aimed to systematically review all propensity score analyses comparing off- and on-pump coronary artery bypass grafting (CABG). Their meta-analysis of 28 studies (100,066 patients) found off-pump CABG superior to on-pump CABG in short-term mortality, the most valid criterion (odds ratio 0.69; 95% confidence interval [CI], 0.60–0.75; P < .0001). Meanwhile, Møller and collaborators' meta-analysis² of 57 randomized trials (5202 patients) showed no significant difference in mortality (relative risk [RR] 0.98; 95% CI, 0.66–1.44). In the future, the largest ongoing randomized trial (CORONARY trial, 4700 patients planned, ClinicalTrials.gov Identifier: NCT00463294) will contribute to the definite answer, as stated by Kuss and colleagues. Shroyer and coworkers³ recently reported the results of another large randomized trial (ROOBY trial, 2203 patients enrolled, not included in Møller and associates' meta-analysis). There was no significant difference between off-pump and on-pump CABG in the rate of death from any cause before discharge or within 30 days after the procedure (1.6% vs 1.2%; RR 1.38; 95% CI, 0.68–2.80; P = .47). Furthermore, even though this result of the ROOBY trial is added to Møller and collaborators' meta-analysis, there is no significant difference in short-term mortality (RR 1.06; 95% CI, 0.67–1.67; P = .80; calculated by us). The evidence from randomized trials obviously demonstrated equivalent short-term mortality between off-pump and on-pump CABG, which is contradictory compared with Kuss and colleagues' results from nonrandomized studies.

Late mortality in off-pump CABG is another concern. In the meta-analysis by Wijeysundera and coworkers,⁴ only 2 observational studies reporting risk-adjusted effects on long-term (≥1 year) outcomes showed essentially no change in mortality (odds ratio 1.01; 95% CI, 0.74–1.40; P = .93). In the ROOBY trial,³ although no significant difference was found for the rate of death from any cause within 1 year (4.1% vs 2.9%; RR 1.41; 95% CI, 0.90–2.24; P = .15), the rate of death from cardiac causes within 1 year was higher in the off-pump group than in the on-pump group (2.7% vs 1.3%; RR 2.05; 95% CI, 1.09–3.86; P = .03). Our recent meta-analysis⁵ of 12 randomized trials (4326 patients enrolled) including the ROOBY trial demonstrated a statistically significant increase in late (≥1 year) all-cause mortality by a factor of 1.37 with off-pump relative to on-pump CABG (RR 1.373; 95% CI, 1.043–1.808; P = .024).

Despite the superiority of off-pump CABG to on-pump CABG in short-term mortality found in Kuss and associates' meta-analysis¹ of propensity score analyses, on-pump rather than off-pump CABG should be considered at least for patients who meet the criteria for enrollment in randomized trials (typically for low- to moderate-risk patients) because late, not short-term, mortality reduction must imply the greatest clinical benefit among patients undergoing CABG.

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References 

1. Kuss O, von Salviati B, Börgermann J. Off-pump versus on-pump coronary artery bypass grafting: a systematic review and meta-analysis of propensity score analyses. J Thorac Cardiovasc Surg. 2010 Feb 16;[Epub ahead of print]
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2. Møller CH, Penninga L, Wetterslev J, Steinbrüchel DA, Gluud C. Clinical outcomes in randomized trials of off- vs. on-pump coronary artery bypass surgery: systematic review with meta-analyses and trial sequential analyses. Eur Heart J. 2008;29:2601–2616
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3. Shroyer AL, Grover FL, Hattler B, Collins JF, McDonald GO, Kozora E, et al. On-pump versus off-pump coronary-artery bypass surgery. N Engl J Med. 2009;361:1827–1837
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4. Wijeysundera DN, Beattie WS, Djaiani G, Rao V, Borger MA, Karkouti K, et al. Off-pump coronary artery surgery for reducing mortality and morbidity: meta-analysis of randomized and observational studies. J Am Coll Cardiol. 2005;46:872–882
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5. Takagi H, Matusi M, Umemoto T. Off-pump coronary artery bypass may increase late mortality: a meta-analysis of randomized trials. Ann Thorac Surg. 2010;89:1881–1888
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