Identifying asymptomatic patients at high-risk for stroke.

Carotid endarterectomy and carotid artery stenting, in addition to good medical therapy, halve long-term stroke risk in asymptomatic patients with carotid artery stenosis. Since the absolute benefits following successful intervention are moderate, identification of asymptomatic patients at high-risk of future stroke could maximize the effectiveness of carotid interventions. The aim of this paper is to summarize the evidence for high-risk features associated with increased long-term stroke risk in asymptomatic patients. There is a paucity of reliable data describing the effect of clinical features, imaging findings and plaque characteristics on increased long-term stroke risk. Clinical and imaging features such as contralateral symptoms, silent brain infarcts/embolic signals, progression of stenosis and impaired cerebrovascular reactivity may be associated with increased future risk of stroke. Plaque characteristics such as echolucency, large plaque size (≥80 mm), intra-plaque hemorrhage, lipid-rich necrotic core and thinned/ruptured fibrous cap may also increase future risk of stroke. Whilst these form the basis for European guidelines targeting carotid intervention in asymptomatic patients with tight stenosis, conclusive evidence of their utility is lacking. Results from ongoing large, multicenter randomized clinical trials comparing carotid endarterectomy and carotid artery stenting with good medical therapy may be consistent with earlier trials, showing a halving of the long-term risk of stroke following successful carotid revascularization. However, they may well lack sufficient statistical power to identify higher-risk subgroups in whom the absolute gains of treatment are significantly higher. Large contemporary cohort studies are needed to provide further clarity regarding high-risk features associated with increased long-term stroke risk in asymptomatic patients with carotid artery stenosis.