Study Findings Challenge Current Clinical Practice
CHICAGO, Nov. 14 -- About one-third of heart attack patients do not receive treatment to open blocked arteries within the recommended 12-hour timeframe after a heart attack. Treatment such as angioplasty or clot-busting drugs may not be given because patients arrive at the hospital too late. For years it has been thought that late balloon angioplasty of these patients' arteries, if they are totally blocked, is still beneficial and might prevent future heart failure, another heart attack, or death. However, according to the results of a large international multi-center clinical trial, stable patients who had angioplasty plus stenting three to 28 days after a heart attack did no better than patients on medical therapy (primarily drug treatment) alone.
The Occluded Artery Trial (OAT) was funded by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health and is being presented today at a late-breaking clinical trial session of the American Heart Association's Scientific Sessions 2006. The study is also published online on November 14 in the New England Journal of Medicine and in the journal's December 7 issue.
"These results challenge the long standing belief that opening a blocked artery is always good. 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," said NHLBI Director Elizabeth G. Nabel, M.D.
"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, M.D., OAT study chair and Harold Snyder Family Professor of Cardiology, Clinical Chief of Cardiology and Director of the Cardiovascular Clinical Research Center, New York University School of Medicine in New York City.
"In general, there is considerable individual variation in the need for angioplasty or bypass surgery in patients who have coronary artery disease."
Hochman expressed concern about a trend in the OAT study toward more heart attacks 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. According to Hochman, it is not known whether the increase in heart attacks will lead to an excess risk of heart failure or death or reduced quality of life.
The OAT trial sought to determine whether performing balloon angioplasty in a totally blocked coronary artery related to a heart attack three to 28 days after the heart attack would benefit stable patients and reduce the risk of future cardiovascular complications. In angioplasty, a thin tube with a balloon or other device on the end is first threaded through a blood vessel in the arm or groin (upper thigh) up to the site of a narrowing or blockage in a coronary artery. Once in place, the balloon is then inflated to push the plaque outward against the wall of the artery, widening the artery and restoring the flow of blood through it.
In OAT, a total of 2,166 patients in 27 countries were randomly assigned to routine angioplasty with stenting combined with drug therapy or to 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 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 for the patients given angioplasty. The primary endpoint or measured result of the 5-year study was a composite of death from any cause, another heart attack, or hospitalization for severe (Class IV) heart failure.
The OAT results found no statistically significant difference 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 in the angioplasty group compared to 15.6 percent of the medical therapy group. 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 heart attacks in the angioplasty group. According to Hochman, when someone has a 100 percent 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. In addition, Hochman said that it is possible that some heart muscle damage due to dislodging of clots and plaque at the time of the angioplasty procedure counteracts other potential long-term benefits.
Each year, about one million people in the United States have a heart attack and half of them (515,000) die. About one-half of those who die do so within 1 hour of the start of symptoms and before reaching the hospital. About one million angioplasty procedures are performed in the US each year.
"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, M.D., chief of NHLBI's Heart Failure and Arrhythmias Branch and member of the OAT study steering committee.
"And we should not forget that controlling the risk factors for heart disease -- such as high cholesterol and high blood pressure - can go a long way toward preventing heart attack in the first place."
To interview Dr. Nabel, or study co-authors Dr. Mascette or Dr. George Sopko of NHLBI, contact the NHLBI Communications Office at 301-496-4236; to interview Dr. Hochman, contact Pamela McDonnell, Office of Public Affairs, NYU School of Medicine at 212-404-3555.