Primary care physicians, cardiologists, and cardiac surgeons have explicitly or implicitly told patients with advanced CAD that with CABG, their angina would be less and their survival chances would be improved. Their decisions about whether to proceed with CABG usually hinged on the belief that these benefits require increasing blood flow in the coronary arteries with surgical revascularization. However, there is no proven cause-and-effect relationship between revascularization and palliation of angina or survival benefit in high-risk groups.
The original theoretical basis for CABG -- that arteries with high-grade stenoses were the most likely to cause heart attacks and death -- is not the case. The extent of high-grade stenoses serves as a marker of the severity of disease, but bypassing stenoses does not reduce the chance of subsequent coronary events at sites of low-graded stenoses or no disease.
The reduction in angina and increased exercise tolerance with CABG compared with medical treatment in high-risk subgroups may well have occurred because of an effect other than revascularization -- the placebo effect (ie, the patient's belief in the efficacy of the therapy), surgically induced infarction of ischemic tissue, denervation of the myocardium, increased motivation to reduce cardiac risk factors, and/or other influences.
Aggressive multiple risk factor reduction programs similar to that of Ornish have greatly reduced angina and given the potential of prolonging life without the pain, suffering, risk, and expense associated with CABG. Therefore, because of the demonstrated effect of CABG to temporally reduce coronary risk factors more than a nonsurgical intervention (ie, BARI data), the survival advantage with CABG is not proven to be due to the surgical revascularization in any subgroup of CAD patients.
If reduced angina and prolonged survival are epiphenomena of CABG not due to the increased blood flow, healthcare costs in the United States might be reduced by more than $26 billion per year, and more than 15,000 operation-related deaths might be avoided with no detriment to healthcare by offering aggressive lifestyle modification programs instead of CABG.
The highly statistically significant coronary risk factor reduction behavioral changes favoring CABG in BARI strongly supports the hypothesis that CABG has temporary survival benefits over medical treatment only because of its effect to temporarily increase motivation for risk factor reduction. Further analysis of the BARI data should be done, looking for any relationship of survival in all subgroups with risk factor reduction behavior. Survival as a function of success in achieving revascularization in both arms of BARI should also be examined. Unfortunately, the publicly funded BARI data are not available to other investigators for these kinds of studies and will not be until the study's completion in 2003. Because of the significance of these questions, the BARI investigators should release the data for independent statistical analysis.
Thanks to Bradley Barton, BS, for research help and to Jay Westbrook, RN, MA, for editing assistance.
© 2002 Medscape
Cite this: Coronary Artery Bypass Grafting (CABG): Reassessing Efficacy, Safety, and Cost - Medscape - Jun 19, 2002.