Correspondence  |   October 2005
Off-pump Coronary Artery Bypass: Randomized Trials, Real-world Experience, Clinical Relevance, and Statistical Significance
Author Notes
  • Royal Hospital for Sick Children, Yorkhill NHS Trust, Glasgow, United Kingdom.
Article Information
Correspondence   |   October 2005
Off-pump Coronary Artery Bypass: Randomized Trials, Real-world Experience, Clinical Relevance, and Statistical Significance
Anesthesiology 10 2005, Vol.103, 901-902. doi:
Anesthesiology 10 2005, Vol.103, 901-902. doi:
To the Editor:—
I read with great interest the editorial by Floyd and Fleisher1 accompanying the article by Cheng et al.  2 in the January issue of Anesthesiology  . They have raised the issue of undertaking further studies recruiting high-risk patients with appropriate controls for important confounders, to compare the impact of off-pump coronary artery bypass (OPCAB) on graft patency and incidence of postoperative stroke, because in their opinion the meta-analysis of Cheng et al.  2 is underpowered to draw conclusions regarding these outcomes. This suggestion of Floyd and Fleisher does not come as a surprise because we are living in an era of evidence-based medicine where statistical significance and not clinical relevance is regarded as the final word.
Since its revival, OPCAB has been under the microscope of skeptics. It has always been the focus of scientific scrutiny, and current medical literature contains a staggering amount of research related to this technique. In fact, among modalities of myocardial revascularization, OPCAB is perhaps the most rigorously tested technique.3 Despite the fact that there is plenty of high-quality evidence from meta-analyses and systematic reviews2,4–7 in support of OPCAB, call for further trials, none of which can ever be large enough to conclusively prove the superiority of OPCAB, seems nothing more than naivety. Instead, it will be much more appropriate to regularly update existing meta-analyses, incorporating outcomes of newly published trials as well as longer-term outcomes of trials already published, according to the concept of cumulative meta-analysis, which was coined by Lau et al.  8 Thereby, the statistical power will increase further, and statistical significance for superiority of OPCAB can be conclusively shown. Moreover, a reanalysis of pooled raw trial data in general will result in more precise effect estimates9 and will provide an opportunity to study the difference in effect between OPCAB and conventional myocardial revascularization more thoroughly, including the influence of preoperative risk factors. To make such pooled reanalysis of raw trial data a success, however, investigators must collaborate and share their raw trial data.
At the same time, it is extremely important to realize that clinical trials are conducted under controlled conditions with strict inclusion and exclusion criteria, and their results may not be translated into “real-world” clinical practice where indications of use of OPCAB are more liberal. Interestingly, real-world clinical experience suggests that a more challenging patient category might benefit most from OPCAB and that OPCAB surgery can be safely performed in high-risk patients with multivessel coronary artery disease.10 In fact, the real-world results of OPCAB are comparable with those of randomized trials and justify the use of OPCAB in unselected patients, with significant economic as well as clinical benefits.3 
To cut things short, it is extremely important to understand that there is abundant clinically relevant, though not necessarily statistically significant, scientific evidence to validate the midterm safety and efficacy of OPCAB. Instead of demanding further trials, it will perhaps be more prudent to accept that the place of OPCAB in the treatment of coronary artery disease is irrefutable and let time decide whether it has statistically significant superiority over conventional on-pump myocardial revascularization for all outcomes in the long term.
Royal Hospital for Sick Children, Yorkhill NHS Trust, Glasgow, United Kingdom.
Floyd T, Fleisher LA: Off-pump coronary artery bypass and the hypothesis from which it grew: Is it yet to be tested? What are the downsides of the lingering questions? Anesthesiology 2005;102:3–5Floyd, T Fleisher, LA
Cheng DC, Bainbridge D, Martin JE, Novick RJ: The 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; 102:188–203Cheng, DC Bainbridge, D Martin, JE Novick, RJ
Raja SG: Safety of off-pump coronary artery surgery: No more skepticism please! (letter). Eur J Cardiothorac Surg 2004; 26:1229Raja, SG
Parolari A, Alamanni F, Cannata A, Naliato M, Bonati L, Rubini P, Veglia F, Tremoli E, Biglioli P: Off-pump versus on-pump coronary artery bypass: Meta-analysis of currently available randomized trials. Ann Thorac Surg 2003; 76:37-40Parolari, A Alamanni, F Cannata, A Naliato, M Bonati, L Rubini, P Veglia, F Tremoli, E Biglioli, P
Reston JT, Tregear SJ, Turkelson CM: Meta-analysis of short-term and mid-term outcomes following off-pump coronary artery bypass grafting. Ann Thorac Surg 2003; 76:1510–5Reston, JT Tregear, SJ Turkelson, CM
van der Heijden GJ, Nathoe HM, Jansen EW, Grobbee DE: Meta-analysis on the effect of off-pump coronary bypass surgery. Eur J Cardiothorac Surg 2004; 26:81–4van der Heijden, GJ Nathoe, HM Jansen, EW Grobbee, DE
Raja SG, Dreyfus GD: Off-pump coronary artery bypass surgery: To do or not to do? Current best available evidence. J Cardiothorac Vasc Anesth 2004; 18:486–505Raja, SG Dreyfus, GD
Lau J, Antman EM, Jimenez-Silva J, Kupelnick B, Mosteller F, Chalmers TC: Cumulative meta-analysis of therapeutic trials for myocardial infarction. N Engl J Med 1992; 327:248–54Lau, J Antman, EM Jimenez-Silva, J Kupelnick, B Mosteller, F Chalmers, TC
Stewart LA, Parmar MK: Meta-analysis of the literature or of individual patient data: Is there a difference? Lancet 1993; 341:418–22Stewart, LA Parmar, MK
Raja SG, Dreyfus GD: Will off-pump coronary artery surgery replace conventional coronary artery surgery? J R Soc Med 2004; 97:275–8Raja, SG Dreyfus, GD