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Most heart attack victims receive no benefit from angioplasty (balloon therapy) procedures performed more than 12 hours after an attack, according to a major cardiology study in which Israel participated.
About one-third of heart attack patients do not receive treatment to open blocked arteries within the recommended 12 hours. For years it has been thought that performing angioplasties of totally blocked coronary arteries even after the 12-hour period helps prevent heart failure, another heart attack or death. But the new international trial found that stable patients who had angioplasty plus stenting three to 28 days after a heart attack did no better than patients on medical therapy (mostly drug treatment) alone.
The results of the Occluded Artery Trial (OAT) were presented at the American Heart Association's Scientific Sessions 2006 in Chicago Tuesday. The study was immediately published on-line in the New England Journal of Medicine and will appear in the journal's December 7 print issue.
The trial included 2,166 people and is the largest and longest study to compare very-late reopening of blocked arteries to medication alone.
Prof. Jonathan Leor, head of the Sheba Medical Center-Tel Aviv University Medical School's cardiac research institute, led the Israeli side of the study, one of 27 countries to participate.
"These results challenge the long standing belief that opening a blocked artery is always good," said Dr. Elizabeth Nabel, director of the US National Institutes of Health's National Heart, Lung, and Blood Institute, which funded the trials. "Instead, the study suggests that late angioplasty is unnecessary in this circumstance. The good news is there have been tremendous advances in drug therapy for heart attack patients. Drug therapy is an important treatment option."
"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," said Dr. Judith Hochman, chairman of the Occluded Artery Trial and a clinical chief of cardiology at New York University Medical School.
Hochman expressed concern about a trend found in the study of more heart attacks in the angioplasty group. Although the data was not statistically significant, she said, it needed to be studied and the patients followed for a longer time to determine if the phenomenon continued or other trends emerged.
Patients were randomly assigned to undergo angioplasty with stenting combined with drug therapy or drug therapy alone. Most patients had blockages in one coronary artery only. Drug therapy for both groups included aspirin, blood-pressure lowering ACE inhibitors, beta blockers, cholesterol-lowering therapy, and clopidogrel, a drug given to patients with stents to prevent blood clots. Patients assigned to undergo angioplasty did so within 24 hours. Stenting, placing a metal mesh tube in the artery to keep it open, was recommended for the patients given angioplasty.
No statistically significant difference was found in major cardiovascular events between the two groups over an average of three years and up to five years. At four years, the rate of death, heart attack, or serious heart failure was 17.2 percent for the angioplasty group compared to 15.6% for the medical therapy group.
The investigators offer a possible explanation for the trend toward more heart attacks in the angioplasty group. Hochman suggested that when someone has a completely blocked artery, the heart muscle may still be somewhat protected by small vessels that provide blood flow from the other coronary arteries. "These vessels are so small that if an easier blood flow path is reestablished via angioplasty, they close down, either temporarily or permanently. If the artery that had the angioplasty re-closes, these small vessels would not be rapidly available to supply blood to your heart muscle at the time of your next heart attack," she said.
Hochman also said it was possible that heart muscle damage due to dislodging of clots and plaque during angioplasty procedures counteracted other 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 Dr. Alice Mascette, a member of the study's steering committee.