NEW YORK, Nov. 14 - In the days following a heart attack, patients who have no or mild symptoms and undergo a procedure called angioplasty to mechanically open their totally blocked coronary arteries do not reduce their risk of having another heart attack, going into heart failure, or dying, according to the results of a new study.
Opening arteries that are 100 percent blocked in the first 12 hours after a heart attack with angioplasty can quickly restore vital blood flow to the heart, and is considered optimal treatment for almost all patients. However physicians in the United States often open blocked coronary arteries with angioplasty in stable patients who are beyond this treatment window, although there aren't any definitive clinical trials addressing this practice.
The study, called the Occluded Artery Trial or OAT, evaluated whether opening arteries three to 28 days after a heart attack benefited patients over the long term. It was designed to provide definitive answers to questions about this practice.
"OAT was created to help resolve a controversy that affects more than 100,000 heart attack survivors each year in the U.S. alone," said Judith S. Hochman, M.D., Director of the Cardiovascular Clinical Research Center at NYU School of Medicine and the lead author of the new study. She estimated that some one-third of eligible patients do not receive therapy to open blocked arteries within the treatment window often because they arrive too late at the hospital.
The study is being published in an early on-line edition of the New England Journal of Medicine to coincide with a presentation of the results by Dr. Hochman on November 14 at the annual meeting of the American Heart Association in Chicago. The study, which was funded by the National Heart, Lung, and Blood Institute of the National Institutes of Health, is expected to be published in Dec. 7, 2006, issue of the journal.
"We had expected that angioplasty to open arteries would reduce the risk of subsequent clinical events, specifically heart failure and death in this population that was stable after the initial heart attack but at increased risk of events in the future," said Dr. Hochman, who is also the Clinical Chief of the Leon H. Charney Division of Cardiology and the Harold Snyder Family Professor of Cardiology at NYU School of Medicine. "We thought it was possible that the risk of a recurrent heart attack would also be reduced. The results were surprising and do warrant a major change in practice."
"Angioplasty has been proven to improve symptoms in patients with angina and to prolong life in patients early after a heart attack," said Dr. Hochman. "This study shows that angioplasty provides no benefit in these patients with a total blockage and no or mild symptoms late after a heart attack. Patients should know whether a procedure is being performed to treat symptoms or whether there is evidence that they will live longer or have a lower likelihood of heart attack or heart failure," she said.
Interventional cardiologists use miniature devices that clear clogged arteries and restore blood flow to the heart to treat heart attack patients. In the study, doctors employed balloon angioplasty, which flattens plaque against the walls of blood vessels by inflating a tiny balloon tethered to the tip of a catheter. Tiny wire tubes called stents were inserted then into the artery to keep the vessel open. The vast majority of the patients who were treated with the balloon procedure had stents implanted at the same time.
"It is critical that patients present immediately after the onset of symptoms of a heart attack," said Dr. Hochman. "If they miss the reperfusion treatment window, they should receive optimal medication therapy. Medical therapy has improved dramatically and those patients did quiet well and better than projected."
A trial on five continents
The OAT study involved 217 sites on five continents. It enrolled 2,166 patients who had a completely blocked coronary artery causing their heart attack, which was identified after the early phase of the heart attack. All of the patients were in stable condition. They were randomly assigned by computer to receive balloon angioplasty and stents plus medical therapy or medical therapy alone three to 28 days after their heart attack. Researchers tracked their health for an average of three years after the heart attack.
There was no statistically significant difference between the two groups in the occurrence of death, heart attacks, or heart failure in up to five years of follow up, according to the study. The researchers also observed a "worrisome" trend toward excess rates of repeat heart attack in the group receiving the angioplasty and stents. Dr. Hochman said that further analysis and longer follow up is necessary to understand this observation, which did not reach the level of statistical significance, so it could have been due to chance alone.
Dr. Hochman speculated that opening a totally blocked artery in a patient who has collateral blood flow may interfere with the ability of the collateral vessels to rapidly supply blood if the opened (stented) artery re-closes. "It seems that total occlusion is a stable situation and this may be converted to a potential risk for recurrent heart attack if the artery is opened and then re-occludes," she said. In addition, it is possible that some heart muscle may be damaged due to dislodging of clots and plaque at the time of the angioplasty procedure, counteracting other potential long-term benefits.