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Ann Thorac Surg 2006;82:769-770
© 2006 The Society of Thoracic Surgeons

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Correspondence

Does Off-Pump Coronary Artery Bypass Graft Surgery Increase Risk of Graft Occlusion?

Department of Cardiovascular Surgery, Shizuoka Medical Center, 762-1 Nagasawa, Shimizu-cho, Sunto-gun, Shizuoka, 411-8611, Japan

(Email: kfgth973{at}ybb.ne.jp).

To the Editor:

We read with great interest the article by Parolari and colleagues [1]. All five studies referred in the meta-analysis are cohort studies. When risks between groups in cohort studies are compared, the appropriate method is to calculate the relative risk (RR). The odds ratio (OR), used in the meta-analysis by Parolari and colleagues [1], is often used in case-control studies and is approximately equal to the RR only when the incidence of the event is low. However, the incidence of postoperative graft occlusion is too high (16% in the off-pump coronary artery bypass surgery [OPCAB] group vs 12% in the standard coronary artery bypass grafting [CABG] group) to justify the use of the OR. Therefore we repeated a meta-analysis using RR rather than OR.

Both separate pooled analyses using a random-effect model of the two low-quality trials [2, 3] (RR, 2.22; 95% CI, 0.51 to 9.59; p = 0.29; significant heterogeneity [p = 0.02]) and the three high-quality trials [4–6] (RR, 1.59; 95% CI, 0.99 to 2.57; p = 0.06; no heterogeneity [p = 0.85]) demonstrated that OPCAB had no impact on risk of graft occlusion. On the other hand, pooled analysis of all five trials [2–6] demonstrated a statistically significant 56% increase in risk of graft occlusion with OPCAB relative to CABG (RR, 1.56; 95% CI, 1.04 to 2.35; p = 0.03; no heterogeneity [p = 0.14]). To assess the impact of qualitative heterogeneity in trial design and patient selection on the pooled effect estimate, we performed several sensitivity analyses by excluding individual trials one at a time and re-calculating the pooled RR estimates for the remaining trials. Exclusion of either the trial by Khan and colleagues [2], the trial by Widimsky and colleagues [3], or the trial by Nathoe and colleagues [5] from the analysis of all five trials did not substantively alter the overall result. However, exclusion of either the trial by Lingaas and colleagues [4] or the trial by Puskas and colleagues [6] demonstrated that OPCAB had no impact on risk of graft occlusion.

In the meta-analysis using OR by Parolari and colleagues [1], a statistically significant increased risk of graft occlusion in the OPCAB group was demonstrated, both when all trials were analyzed together and when low-quality and high quality trials were analyzed separately. Nevertheless, in our re-analysis using RR more appropriate than OR, the statistically significant increased risk vanished when low-quality and high-quality trials were analyzed separately, and in two of five sensitivity analyses.

	References

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1. Parolari A, Alamanni F, Polvani G, 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]
2. 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;350:21-28.[Abstract/Free Full Text]
3. Widimsky P, Straka Z, Stros P, et al. One-year coronary bypass graft patencya 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]
4. Lingaas PS, Hol PK, Lundblad R, et al. Clinical and angiographic outcome of coronary surgery with and without cardiopulmonary bypassa prospective randomized trial. Heart Surg Forum 2004;7:37-41.[Medline]
5. Nathoe HM, van Dijk D, Jansen EW, 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]
6. 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.[Abstract/Free Full Text]

This article has been cited by other articles:

				A. Parolari, F. Alamanni, F. Veglia, E. Tremoli, and P. Biglioli Reply Ann. Thorac. Surg., August 1, 2006; 82(2): 770 - 771. [Full Text] [PDF]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Hisato Takagi Takuya Umemoto Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Takagi, H. Articles by Umemoto, T. Search for Related Content PubMed PubMed Citation Articles by Takagi, H. Articles by Umemoto, T. Related Collections Coronary disease Related Article