Angiographically Defined Collateral Circulation and Risk of Stroke in Patients With Severe Carotid Artery Stenosis

Abstract

Background and Purpose-Blood supply through collateral pathways improves regional cerebral blood flow and may protect against ischemic events. The effect of collaterals on the risk of stroke and transient ischemic attack (TIA), in the presence of angiographic severe internal carotid artery (ICA) stenosis, was assessed. Methods-Angiographic collateral filling through anterior communicating and posterior communicating arteries and retrograde filling through ophthalmic arteries were determined in all patients at entry into the North American Symptomatic Carotid Endarterectomy Trial. Kaplan-Meier event-free survival analyses were performed on 339 medically treated and 342 surgically treated patients. Results-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% (Pϭ0.005). Similar reductions were observed for hemispheric TIA (36.1% versus 19.1%; Pϭ0.008) and disabling or fatal strokes (13.3% versus 6.3%; Pϭ0.11). For surgically treated patients, the perioperative risk of hemispheric stroke was 1.1% in the 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 group was statistically significant. The observed reductions were independent of the degree of ICA stenosis and other vascular risk factors. Conclusions-Collaterals

High blood pressure is inversely related with the presence and extent of coronary collaterals

“…Two studies, in patients with carotid artery disease, 37 also reported a lower prevalence of cerebral collateral circulation among the patients with hypertension. Yet, three other studies 9 found hypertension to be positively associated with the presence of CCs.…”

Significance of the perfusion‐diffusion mismatch in chronic cerebral ischemia

“…In particular, patients with symptomatic ICA occlusion have deteriorated cerebral hemodynamics and metabolism (26). However, when the collaterals were demonstrated angiographically, the patients were shown to bear a lower risk of hemispheric stroke or transient ischemic attack (TIA) (29). MRA is a sensitive tool for assessing occlusive artery disease in stroke with a high concordance with perfusion abnormalities in the acute situation (30 -32).…”

Normal Variants of the Circle of Willis in patients undergoing CT Angiography

“…Those patients with variants of the circle with efficient collateral circulation have a lower risk of transient ischemic attack and stroke than that of patients without such collaterals. 4,5 CT angiography (CTA) allows reliable non-invasive evaluation of the intracranial arteries. Moreover, CTA provides useful information about anatomical variations of cerebral circulation, with reported high sensitivity and specificity (81-90% and 93%, respectively), approaching the diagnostic accuracy of digital subtraction angiography.…”