Clopidogrel reduces risk of adverse events for patients with acute coronary syndromes undergoing balloon angioplasty

Patients with acute coronary syndromes who were pre-treated with the anti-platelet agent clopidogrel before undergoing a procedure such as balloon angioplasty or stent placement had a reduced risk of adverse events if they received the anti-clotting drug abciximab, according to a study that will appear in the April 5 issue of JAMA: The Journal of the American Medical Association.

The study is being released early online to coincide with its presentation at the American College of Cardiology annual conference.

Non -ST-segment elevation (a certain pattern on an electrocardiogram) acute coronary syndromes (ACS - a spectrum of conditions involving chest discomfort or other symptoms) are associated with an increased risk of death and are a major reason for hospital admissions. Although percutaneous coronary interventions (PCIs - procedures such as angioplasty or stent placement used to open narrowed coronary arteries) are an established therapeutic approach in high-risk patients presenting with ACS, it is still unclear what the best adjunctive antithrombotic therapies are, according to background information in the article. There is increasing evidence that treatment with clopidogrel prior to PCI prevents postprocedural ischemic complications. It is not known whether the antiplatelet effect provided by 600 mg of clopidogrel eliminates the need for more potent antiplatelet therapies in patients with ACS undergoing PCI.

Adnan Kastrati, M.D., of the Deutsches Herzzentrum, Munich, Germany and colleagues with the ISAR-REACT 2 Trial assessed whether abciximab is a useful therapy in patients with non -ST-segment elevation ACS undergoing PCI, even after pretreatment with a 600-mg loading dose of clopidogrel. The randomized, double-blind, placebo-controlled trial included 2,022 patients and was conducted from March 2003 through December 2005. The patients, with non -ST-segment elevation ACS undergoing PCI, were assigned to receive either abciximab or placebo. All patients received clopidogrel, 600 mg, at least 2 hours prior to the procedure, as well as 500 mg of oral or intravenous aspirin.

The primary end point of death, heart attack, or urgent target vessel revascularization occurring within 30 days after randomization was reached in 90 patients (8.9 percent) assigned to abciximab vs. 120 (11.9 percent) assigned to placebo. Thus, there was a significant 25 percent relative reduction of the risk with abciximab. Most of the risk reduction caused by abciximab resulted from a reduction in the occurrence of death and heart attack.

There was no difference in the incidence of ischemic events between the abciximab group and the placebo group among patients without an elevated troponin (muscle protein that is elevated in patients with cardiac ischemia) level. However, among patients with an elevated troponin level, the incidence of ischemic events was significantly lower (29 percent reduced risk) in the abciximab group (13.1 percent) compared with the placebo group (18.3 percent). There were no significant differences between the 2 groups regarding the risk of major and minor bleeding as well as need for transfusion.

"The benefits of abciximab appear to be confined to patients with an elevated troponin level," the authors conclude.