Participants were randomly assigned to conventional medical therapy, including the most popular drugs to control diabetes, or to a surgical procedure -- stenting or bypass surgery at the physician's discretion.
With drugs, the researchers maintained all patients at the same blood sugar level.
Although the study showed no overall advantage for either kind of treatment, bypass surgery did show a slight advantage over stents and non-surgical treatment in preventing the occurrence of future serious coronary events -- but not death.
This finding was striking, said co-author Dr. Robert Frye, also a Mayo Clinic cardiologist.
"It's the first demonstration in a properly conducted randomized trial that -- in patients with mild symptoms and stable ischemic heart disease -- coronary bypass reduces these events," he said at a news conference Sunday regarding the findings.
In its editorial, the New England Journal of Medicine stopped short of a flat-out endorsement of drug treatment over surgical intervention.
Instead, it called non-surgical therapy "an excellent first-strategy, particularly for those with less severe disease." But for those with more serious coronary artery blockage and symptoms, it said, "revascularization is appropriate," using either strategy.
Critics of the study noted that the results might not be applicable to a population with unstable heart disease and other populations.
Still, the study suggests there are many patients who could safely start with the less expensive, less intensive and more prevention-oriented therapies, according to the Mayo Clinic's Thomas.
These patients may represent "low hanging fruit" for reducing health care expenses while still administering appropriate therapy, he said.
The annual cost of health care for an adult with diabetes is about $10,000, compared with around $3,000 for a non-diabetic adult.
The study was supported by grants from the National Heart, Lung and Blood Institute and the National Institute of Diabetes and Digestive and Kidney Diseases; and by GlaxoSmithKline, Lantheus Medical Imaging, Astellas Pharma, Merck, Abbott Laboratories, Pfizer, MediSense, Bayer, Becton Dickinson, J.R. Carlson Labs, Centocor, Eli Lilly, LipoScience, Novartis, and Novo Nordisk.
Orchard reported receiving consulting fees from AstraZeneca, Eli Lilly, and Takeda and grant support from VeraLight and having an equity interest in Bristol-Myers Squibb.
Co-authors reported conflicts of interest with sanofi-aventis, Schering-Plough, Axio, Eli Lilly, CV Therapeutics, Takeda, Merck, Blue Cross Blue Shield Technology Evaluation Center, GE Healthcare, Aviir, Amgen, Tercica, Corcept Therapeutics, and GlaxoSmithKline.
Thomas reported being part of a group that has received research grants from Omron, Blue Cross-Blue Shield of Minnesota, and the Marriott Family Foundation.