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The presence of collaterals supplying the symptomatic ICA increased with severity of stenosis. Two-year risk of hemispheric stroke in medically treated patients with severe ICA stenosis was reduced in the presence of collaterals: 27.8% to 11.3% (P=0.005). Similar reductions were observed for hemispheric TIA (36.1% versus 19.1%; P=0.008) and disabling or fatal strokes (13.3% versus 6.3%; P=0.11). For surgically treated patients, the perioperative risk of hemispheric stroke was 1.1% in th e presence of collaterals versus 4.9% when absent. The 2-year stroke risks for surgical patients with and without collaterals were 5.9% versus 8.4%, respectively. Neither comparison in the surgical groups was statistically significant. The observed red uctions were independent of the degree of ICA stenosis and other vascular risk factors. Collaterals are associated with a lower risk of hemispheric stroke and TIA, both long term and perioperatively. Angiographic identification of collaterals assists in identifying patients with severe ICA stenosis at lower risk of stroke and TIA. |
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