Review: On-pump CABG should remain standard treatment

Source: Siemens Healthcare, image courtesy of Columbia Radiology Imaging, Columbia, Mich.

Off-pump compared with on-pump CABG surgery offered no significant mortality, stroke or MI benefit, based on a systematic review published March 14 in the Cochrane Review. The review found patients with ischemic heart disease who underwent on-pump CABG with the use of cardiopulmonary bypass and cardioplegic arrest had better long-term survival than did patients who received an off-pump procedure.

Christian H. Moller, MD, of the cardiothoracic surgery department at Copenhagen University Hospital in Denmark, and colleagues explained that systemic reviews have been published on on- and off-pump CABG, but new evidence has emerged since the last review in 2008. This prompted them to conduct their analysis, based on a search of the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, Science Citation Index Expanded on ISIWeb of Science and CINAHL, up to February 2011.  

They identified 86 trials comparing on- and off-pump CABG, 10 of which they deemed at low risk of bias, for a total of 10,716 patients. They used statistical analyses and trial sequential analyses to determine results.

In analyses using all trials, they found that off-pump CABG increased all-cause mortality compared with on-pump CABG, 3.7 percent vs. 3.1 percent. An analysis of only trials at low risk of bias placed all-cause mortality at 6.2 percent for off-pump CABG vs. 4.6 percent for on-pump CABG. They found no significant differences in MI, stroke, renal insufficiency or coronary re-intervention between the two approaches.

The researchers noted a reduction in post-operative atrial fibrillation in the off-pump group compared with the on-pump group in analyses based on all trial data but they noted a great deal of variation among the trials. In an analysis based on the 10 trials considered at low risk of bias the estimated effect was no longer significantly different. Off-pump CABG resulted in fewer distal anastomoses.

“No statistically significant differences regarding myocardial infarction, stroke, coronary re-intervention, or renal insufficiency were demonstrated in the meta-analyses,” Moller and colleagues wrote. “However, this does not mean that difference does not exist. Off-pump CABG resulted in significantly fewer distal anastomoses, indicating increased risk of incomplete revascularization.”

They wrote that previous reviews of randomized trials comparing on-pump and off-pump CABG have shown a benefit in the off-pump approach while they found a significant difference in all-cause mortality. They argued that their review included extended follow-up and a much larger number of patients, providing the power for their analyses.

 They also looked at funding source to explore the possibility of vested interest bias. “In trials without funding from the device industry we found a significant harmful effect of off-pump CABG whereas trials with high risk of vested interests showed no inferiority of off-pump CABG,” they wrote.

They acknowledged study limitations, including limitations within the individual trials, the selective patient population seen in some randomized clinical trials and their inability to assess surgeon experience and skill level in their review.

They concluded that, based on their review, on-pump CABG should remain the standard surgical treatment, with off-pump CABG acceptable for patients with contraindications to aortic cannulation and cardiac arrest. They recommended researchers design future randomized trials to assess both benefits and harms of on-pump and off-pump CABG, minimize bias, include large patient sample sizes and incorporate mechanisms to compare surgeon experience.