Coronary Artery Bypass Grafting (CABG): Reassessing Efficacy, Safety, and Cost

David K. Cundiff

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In This Article

Abstract and Introduction

Abstract

Based on randomized clinical trials begun in the 1970s showing the superiority of coronary artery bypass grafting (CABG) to medical management for patients with coronary artery disease (CAD), CABG has been routinely used to reduce angina and improve chances of survival in patients with CAD. Since CABG became a recognized standard treatment of CAD, considerable evidence has accumulated concerning the pathogenesis of CAD; the efficacy, risks, and costs of CABG; and the effectiveness of CAD risk factor reduction. To re-evaluate efficacy, safety, and cost of CABG, a MEDLINE search was performed to locate randomized trials comparing CABG vs nonsurgical management, CAD pathogenesis studies, and articles evaluating efficacy of coronary artery risk factor reduction behaviors.

The extent of revascularization with CABG bore no relationship to relief of angina or survival. Randomized CABG vs medical management studies revealed that only patients with the most advanced CAD had improved survival, and this advantage vanished after 12 years. Researchers kept little coronary risk factor reduction data in the original CABG vs medical management randomized trials. However, in the Bypass Angioplasty Revascularization Intervention (BARI) study, surgically treated patients adopted lifestyles associated with lower coronary risk significantly more than patients treated with angioplasty. Factors other than revascularization cause the improvement in angina associated with CABG. Temporary survival advantages of CAD high-risk subgroups after CABG may be better explained by risk factor reduction rather than by revascularization. Using the BARI data, including lifestyle factors, a multivariate analysis of the influences determining survival and quality-of-life end points would test this hypothesis.

Introduction

In the 1960s, cardiac surgeons based their rationale for proposing CABG as a treatment for CAD on the belief that high-grade coronary artery stenoses tend to progress to complete obstruction, acute myocardial infarction (AMI), and possibly death.[1,2] While the original randomized trials did not show a significant overall survival benefit with CABG, the experimental validation of the survival advantages of the procedure came from data analyses of subgroups of patients randomized to surgery vs medical management.[3,4,5,6,7] By the late 1970s, cardiologists and cardiac surgeons thought that CABG, the most studied procedure in the history of surgery, improved chances for patients in selected high-risk groups to live longer, dramatically reduced angina, and enhanced quality of life.

An American Heart Association position statement, updated in 1991 and 1999, declared that CABG is indicated if medical management does not satisfactorily control angina in patients with CAD or if the patient has > 50% obstruction of the left main coronary artery or 3-vessel disease with moderate or severe left ventricular dysfunction regardless of symptoms.[8,9]

In light of data reported subsequent to the acceptance of CABG as established therapy in the late 1970s, this paper will reanalyze the underlying rationale and the experimental validation that CABG relieves symptoms and prolongs life in patients with CAD. First, let us look at the evidence that CABG improves quality of life.

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