The OAT Trial shows that angioplasty with stenting delayed by three days or more after a myocardial infarction is no more effective than medical therapy alone in stable patients, according to a presentation at a Late-Breaking Clinical Trials session at the American Heart Association meeting.

About one third of patients admitted with acute myocardial infarction do not undergo revascularization within the recommended 12-hour timeframe. The Occluded Artery Trial (OAT) was funded by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health and was published online on November 14 by the New England Journal of Medicine.

"Our findings indicate that routine late opening of the heart attack related coronary artery is not appropriate and should be reserved only for certain patients such as those who are unstable or continue to have chest pain following a heart attack. These results should lead to lower rates of unnecessary coronary interventions in this specific group of stable patients," said Judith Hochman, MD, OAT study chair and Director of the Cardiovascular Clinical Research Center, New York University School of Medicine in New York City.

Hochman expressed concern about a trend in the OAT study toward more recurrent infarctions in the angioplasty group. Although the trend was not statistically significant, she said, it needs to be studied and the patients followed for a longer time to determine if the trend continues or whether other trends emerge.

In OAT, a total of 2,166 stable patients in 27 countries were randomized to routine angioplasty with stenting combined with drug therapy or to drug therapy alone. Most patients had occlusion in one coronary artery only.

Drug therapy for both groups included aspirin, angiotensin converting enzyme inhibitors, beta blockers, cholesterol-lowering therapy, and clopidogrel. Patients assigned to undergo angioplasty were given the procedure within 24 hours of treatment assignment. Stenting, placing a metal mesh tube in the artery to keep it open, was recommended.

The primary endpoint of the 5-year study was a composite of death from any cause, recurrent infarction, or hospitalization for severe heart failure. There was no statistically significant difference in major cardiovascular events between groups over an average of three years and up to five years.

At four years, the rate of death, recurrent infarction, or serious heart failure was 17.2 percent for angioplasty compared with 15.6 percent for medical therapy. The results were consistent across study sites located in the United States and in other countries.

The OAT investigators offer a possible explanation for the trend toward more recurrent infarctions in the angioplasty group. According to Hochman, collateral vessels may close either temporarily or permanently after revascularization of the major artery and not be available as a significant source of blood flow if restenosis occurs. In addition, Hochman said it is possible that some myocardial damage due to dislodging of clots and plaque at the time of the angioplasty procedure counteracts other potential long-term benefits.

"There's an important public health lesson to be learned from the OAT trial results: seek care very early after heart attack symptoms begin because that's when there is a great deal of benefit from angioplasty," said Alice Mascette, MD, a member of the OAT study steering committee.