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Atherosclerosis is a systemic disease affecting arteries throughout the body. Multiple factors including hypertension, diabetes, hyperlipidemia, and family history influence stroke and TIA risk (Table 17-5). Cardioembolic risk factors include atrial fibrillation/flutter, MI, valvular heart disease, and cardiomyopathy. Hypertension and diabetes are also specific risk factors for lacunar stroke and intraparenchymal hemorrhage. Smoking is a potent risk factor for all vascular mechanisms of stroke. Identification of modifiable risk factors and prophylactic interventions to lower risk is probably the best approach to stroke overall.
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Platelet antiaggregation agents can prevent atherothrombotic events, including TIA and stroke, by inhibiting formation of intraarterial platelet aggregates. Aspirin (50–325 mg/d) inhibits thromboxane A2, a platelet aggregating and vasoconstricting prostaglandin. Aspirin, clopidogrel (blocks the platelet adenosine diphosphate [ADP] receptor), and the combination of aspirin plus extended-release dipyridamole (inhibits platelet uptake of adenosine) are the antiplatelet agents most commonly used. In general, antiplatelet agents reduce new stroke events by 25–30%. Every pt who has experienced an atherothrombotic stroke or TIA and has no contraindication should take an antiplatelet agent regularly because the average annual risk of another stroke is 8–10%. The choice of aspirin, clopidogrel, or dipyridamole plus aspirin must balance the fact that the latter are marginally more effective than aspirin but the cost is higher.
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In pts with atrial fibrillation and stroke, anticoagulants are generally the treatment of choice.
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Anticoagulation Therapy for Noncardiogenic Stroke
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Data do not support the use of long-term warfarin for preventing atherothrombotic stroke for either intracranial or extracranial cerebrovascular disease.
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Carotid Revascularization
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Carotid endarterectomy benefits many pts with symptomatic severe (>70%) carotid stenosis; the relative risk reduction is ~65%. However, if the perioperative stroke rate is >6% for any surgeon, the benefit is questionable. Endovascular stenting is an emerging option; there remains controversy as to who should receive a stent or undergo endarterectomy. Surgical results in pts with asymptomatic carotid stenosis are less robust, and medical therapy for reduction of atherosclerosis risk factors plus antiplatelet medications is generally recommended in this group.
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For a more detailed discussion, see Smith WS, Johnston SC, Hemphill JC III: Cerebrovascular Diseases, Chap. 446, p. 2559, in HPIM-19.