New antiplatelet strategies in stroke prevention and treatment
Stroke represents the third leading cause of death in the United States, even though its incidence has decreased over the past several decades; it remains a major health problem worldwide. Overall, about 80% of strokes are ischemic, usually representing acute occlusive events in a setting of vascular disease. Twenty-five to 30% of non-hemorrhagic strokes included in stroke registries are clearly related to atherosclerosis, 20% to cardiac thromboemboli, 5% to hematologic disorders, 8% to small vessel occlusion due to lipohyalinosis or vasculitis, the rest being of undetermined or mixed cause. Substantial evidence from epidemiological and clinical studies indicates that recurrent ischemic stroke can be prevented by antiplatelet therapy (Antiplatelet Trialists’, 1994) and that control of risk factors not only is important for preventing a first stroke but also for secondary prevention after a first ischemic event. These risk factors include hypertension, cigarette smoking, coronary artery disease, diabetes mellitus, dyslipidemia, heavy alcohol consumption, thrombocytosis, erythrocytosis and asymptomatic carotid artery stenosis (Wolf et al., 1999). Preexisting cardiovascular diseases such as coronary artery disease, prior myocardial infarction, valvular heart disease, congestive heart failure, atrial fibrillation, increased left ventricular mass and certain other echocardiographic abnormalities, identify persons at increased risk of stroke who may benefit from antithrombotic therapy including antiplatelet agents (National Stroke Association, 1999). The continued search for better antithrombotic agents in ischemic stroke rests on the observation that, overall, 75% to 80% of strokes involve thrombotic events while current therapies offer <25% risk reduction (del Zoppo, 1999).