Combination antiplatelet agents for secondary prevention of ischemic stroke

Abstract

Stroke is a leading cause of death and the primary cause of serious, long-term disability in the United States. Joint guidelines from the American Heart Association (AHA) and American Stroke Association (ASA), as well as recent guidelines from the Eighth American College of Chest Physicians (ACCP) Conference on Antithrombotic and Antiplatelet Therapy, recommend aspirin, clopidogrel, or extended-release dipyridamole plus aspirin as acceptable first-line options for secondary prevention of ischemic events in patients with a history of ischemic stroke or transient ischemic attack (TIA). The ACCP strongly recommends the combination of extended-release dipyridamole plus aspirin over aspirin monotherapy (highest level of evidence) and suggests clopidogrel monotherapy over aspirin monotherapy (lower level of evidence). The AHA-ASA guidelines suggest that either extended-release dipyridamole plus aspirin or clopidogrel monotherapy should be used over aspirin monotherapy. Both guidelines recommend avoiding the combination of clopidogrel and aspirin for most patients with previous stroke or TIA. Results from recent trials evaluating combination antiplatelet therapy have been published that enhance the AHA-ASA recommendations and provide the foundation for the updated ACCP guideline. To identify pertinent combination antiplatelet trials, a MEDLINE search of the literature from 1967-2007 was performed. Two trials were identified--the European-Australasian Stroke Prevention in Reversible Ischemia Trial (ESPRIT) and Clopidogrel for High Atherothrombotic Risk and Ischemic Stabilization, Management, and Avoidance (CHARISMA). The ESPRIT compared aspirin monotherapy with the combination of aspirin plus extended-release dipyridamole for prevention of secondary ischemic events in patients with a history of TIA or minor stroke. The CHARISMA trial compared aspirin plus clopidogrel with aspirin alone in a population at high risk for atherothrombotic events using the composite outcome of myocardial infarction, stroke, and death from cardiovascular causes. Data from ESPRIT add to evidence that the combination of aspirin plus extended-release dipyridamole is superior to aspirin alone. The findings of the CHARISMA trial reinforce recommendations from both AHA-ASA and ACCP that the combination of aspirin and clopidogrel be reserved for special populations requiring this antiplatelet combination (e.g., those who have had coronary artery stenting).