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Stroke risk and critical carotid stenosis.
  1. J W Norris,
  2. C Z Zhu
  1. Stroke Research Unit, Sunnybrook Medical Centre, University of Toronto, Canada.


    The risk of stroke from carotid stenosis is proportionate to the degree of stenosis, but whether this is a direct and linear relationship is unknown. Using the degree of carotid stenosis in 500 patients with asymptomatic carotid bruits as a continuous variable, we plotted the frequency distribution and related this to the risk of ischaemic cerebral events and the progression of the arterial lesion. There was a bi-modal distribution, with the junction of the two populations at 85% stenosis. The frequency of ischaemic cerebral events was maximal at 75-90% stenosis. Our data suggest that there is a critical degree of carotid stenosis at which stroke risk becomes maximal. This may represent a window of therapeutic opportunity.

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