Stroke risk factors and development of collateral flow in carotid occlusive disease

Background and purpose - Blood now through collateral vessels compensates for reduced blood now through stenotic or occluded extracranial carotid arteries. Previous studies have shown that extent of collateral flow influences likelihood of stroke and its outcome. Here we analyzed the relationship between stroke risk factors (hypertension, coronary artery disease, diabetes mellitus, tobacco smoking and hypercholesterolemia) and number of patent intracranial collaterals detected by transcranial Doppler ultrasonography. Subjects and methods - We studied 182 patients with various degrees of angiography proven unilateral stenosis of the internal carotid artery. Contribution of the anterior and posterior communicating arteries to the perfusion of the cerebral hemisphere on the side of the stenosis or occlusion was evaluated by a series of compression tests performed during continuous insonation of the middle cerebral artery. The number of detected collateral vessels was correlated with analyzed stroke risk factors. Results - Subjects with stenosis more than 75% or occlusion of the internal carotid artery had a higher frequency of two major intracranial collateral vessels (P less than or equal to 0.01 and P less than or equal to 0.001, respectively), Hypertensive patients with stenosis more than 75% or total carotid occlusion were more likely to have only a single collateral vessel than patients without hypertension (P less than or equal to 0.01 and P less than or equal to 0.05, respectively). Other risk factors did not influence the patency of preformed collateral vessels. Conclusions - Hypertension hindered the development of preformed intracranial collateral vessels in our patients with carotid occlusive disease.