ABSTRACT
Atherosclerotic cerebrovascular disease Atherosclerosis accounts for up to one-third of all strokes. Approximately 50% of strokes occur in the territory of the carotid arteries, and while extracranial carotid disease is more frequent in Caucasians, intracranial disease is more frequent in non-whites ( Figure 6.4 ). 27-29 Carotid disease that is amenable to revascularization accounts for 5-12% of new strokes. 30-32 Carotid atherosclerosis is typically unifocal, and 90% of lesions are located within 2cm of the origin of the internal carotid artery (ICA) (see Figure 6.4 ). 4,33 The degree of carotid stenosis is associated with stroke risk in symptomatic patients. Carotid atherosclerosis can produce retinal and cortical symptoms by either progressive carotid stenosis leading to hypoperfusion (less commonly) or by intracranial arterial embolization (more commonly). The risk of progression of carotid stenosis is 9.3% per year, and risk factors for progression include: 34
■ ipsilateral or contralateral ICA stenosis greater than >50%; ■ ipsilateral external carotid artery (ECA) stenosis >50%; and ■ systolic blood pressure >160 mmHg. 34
Medical therapy A demographic profile can gauge the risk of stroke based on age, systolic blood pressure, antihypertensive therapy, diabetes,
cigarette smoking, and history of coronary artery disease (CAD), congestive heart failure, or atrial fibrillation. 35,37 Clinical findings must be correlated with brain and vascular imaging to determine whether or not suspected atherosclerotic cerebrovascular disease is symptomatic. Imaging is critical to assess the anatomy and structural pathology of the brain (e.g. mass, old or new stroke, presence of hemorrhage) and the cervical vessels (e.g. stenosis, plaque morphology, dissection), and to guide treatment. In asymptomatic patients there are no guidelines to support routine carotid imaging, except for some candidates for coronary artery bypass grafting (CABG.) Prior to CABG, carotid duplex studies are recommended in asymptomatic patients who are older than 65 years or who have left main coronary artery stenosis; peripheral arterial disease; a history of smoking, TIA, or stroke; or a carotid bruit. 12
Hypertension is major risk factor for all forms of cerebrovascular disease by virtue of its direct atherogenic effects on the systemic and cerebral circulations, and by association with CAD and atrial fibrillation. 38 Control of blood pressure is key to modification of atherogenic risk factors: there is a linear
Figure 6.1 NASCET Kaplan-Meier survival curves for stroke in symptomatic patients with severe carotid stenoses treated by surgery (red) or best medical therapy (blue). (Reprinted with permission from Barnett et al. 10 )
Figure 6.2 Survival curves for asymptomatic patients with severe carotid stenoses treated with endarterectomy and medical therapy. TIA, transient ischemic attack. Reprinted with permission from: Endarterectomy for Asymptomatic Carotid Artery Stenosis. JAMA 1995; 273: 1421-28.
