title: Critical stenosis of the internal carotid artery.
abstract: To better define the hemodynamic significance of internal carotid artery stenosis, intraoperative electromagnetic blood flow measurements were taken in 47 patients before and after carotid endarterectomy. When the ratio of pre- to postendarterectomy blood flew (Qpre/Qpost = Y) is compared to the fractional percent of internal carotid artery stenosis (X), the linear regression lines for the 25 arteries with Qpre/Qpost less than 0.70 are Y = -2.67 x +2.59 and Y = -10.10 x +10.06, respectively, for diameter and area stenosis. The intercepts of the regression lines with (a) Qpre/Qpost = 1 (normal blood flow) are 60% diameter and 90% are stenosis, (b) Qpre/Qpost = 0.60 (40% reduction in blood flow) are 75% diameter and 94% are stenosis and (c) with Qpre/Qpost = 0.36 (64% reduction in blood flow) are 84% diameter and 96% area stenosis. These data indicate that a critical or hemodynamically significant internal carotid artery stenosis may be of a higher grade than previously appreciated and that a stenosis greater than 75% diameter or 94% area may be necessary to symptomatically reduce cerebral blood flow.
mesh_terms: D001783:Blood Flow Velocity; D002340:Carotid Artery Diseases / Q000601:surgery*; D002343:Carotid Artery, Internal / Q000503:physiopathology / Q000601:surgery*; D003251:Constriction, Pathologic; D004691:Endarterectomy; D006801:Humans