Diabetes Health Center

Clinical Alert: Bypass Over Angioplasty for Patients with Diabetes

The National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health, today announced that, as a first revascularization procedure, coronary artery bypass graft (CABG) surgery has been shown to have a markedly lower 5-year death rate than angioplasty for persons with diabetes mellitus (Type I or II) who are on oral hypoglycemic agents or insulin.

The finding came from the NHLBI-funded Bypass Angioplasty Revascularization Investigation (BARI). The multicenter, international, randomized trial studied patients who needed a first revascularization because of severe ischemia with obstructions in two or more major coronary arteries. Over 5 years, patients with diabetes mellitus who were on drug therapy had a significantly lower (p=0.002) mortality rate with CABG, compared with percutaneous transluminal coronary angioplasty (PTCA). The 5-year CABG mortality rate was 19 percent, compared with 35 percent for PTCA. By contrast, in patients without diabetes and in those with diabetes but not on drug treatment, the 5-year mortality rates for CABG and PTCA were both about 9 percent.

The higher death rate for PTCA was not due to complications of the procedure itself. Those with diabetes are known to have an excessive cardiovascular risk and a higher mortality rate was expected for them, regardless of revascularization procedure. However, the excess mortality with PTCA had not been anticipated.

BARI's results indicate that CABG should be the preferred treatment for patients with diabetes on drug or insulin therapy who have multivessel coronary artery disease and need a first coronary revascularization. These results have a significant impact on the clinical care of these patients.

Coronary revascularization plays an important role in the treatment of clinically severe coronary artery disease. The two most commonly used methods of revascularization are CABG and PTCA. PTCA is a catheter-based nonsurgical approach that directly targets coronary obstructions by dilation of the vessel at the point of obstruction. The process is accompanied by local vascular injury and subsequent healing. The extent of injury and the healing process may be different in diabetic and nondiabetic patients. Not all lesions can be dilated, due largely to technical reasons. CABG is a major operation, requiring opening of the chest. It provides a new channel, with a lumen frequently larger than the native, diseased lumen. There is no instrumentation of the local lesion and, therefore, no related vascular injury. While both treatments alleviate the effects of coronary artery disease, they do not correct or alter the natural course of the disease.

Before PTCA, CABG was the traditional revascularization strategy. But PTCA, first performed in the United States in 1977, has grown rapidly in use. In 1993, about 362,000 PTCAs were done in the United States, compared with about 309,000 CABG surgeries.

However, PTCA use has expanded not just in number but also in the type of patient treated. Initially, PTCA was done on patients with one obstructed vessel. But, with increased physician expertise and an improved technology, PTCA use has rapidly expanded to include patients with more complex, multivessel coronary obstructions, once treated exclusively with CABG. This has led to uncertainties about the long-term effectiveness and safety of PTCA compared with CABG and prompted the NHLBI to fund a rigorous evaluation of the two methods.