Cerebral hemodynamics in patients with carotid artery occlusion and contralateral moderate or severe internal carotid artery stenosis

Object. The purpose of this study was to evaluate cerebral hemodynamics in patients suffering from occlusion of the carotid artery (CA) and contralate ral CA stenosis. Methods. Using transcranial Doppler ultrasonography, the cerebrovascular re activity to hypercapnia in the middle cerebral arteries was evaluated by ca lculating the breath-holding index (BHI) of 69 symptomatic patients sufferi ng from internal CA (ICA) occlusion and moderate or severe contralateral IC A stenosis. To evaluate which variables influenced BHIs ipsilateral to the site of ICA occlusion, a multiple stepwise linear regression analysis was p erformed that included the following factors: patient age, percentage of co ntralateral ICA stenosis, contralateral BHI, number of collateral pathways, and presence of hypertension, diabetes, smoking, and hyperlipidemia. An an alysis of variance was conducted to evaluate the impact of the type of coll ateral vessels on the BHI. A regression analysis showed that the BHI ipsila teral to the site of ICA occlusion could be accounted for by the contralate ral BHI (which was entered at the first step of the analysis, p < 0.001) an d by the number of collateral pathways (which was entered at the second ste p, p = 0.033). Neither the degree of contralateral ICA stenosis nor the oth er variables could be added to improve the model. The analysis demonstrated that the absence of collateral pathways and the presence of the anterior c ommunicating artery (ACoA) alone were associated with lower BHI values than those found in the presence of two or three collateral vessels, regardless of the presence of an anterior collateral pathway. Conclusions. On the basis of these data one can infer that the cerebral hem odynamic status of patients with occlusive disease of the CA is influenced by individual anatomical and functional characteristics. Because improvemen t in contralateral hemodynamics after surgical correction of an ICA stenosi s can only be expected in the presence of an ACoA, the planning of strategi es for influencing cerebral blood flow distal to an ICA occlusion and, in p articular, the consideration of a contralateral carotid endarterectomy, sho uld be preceded by a careful evaluation of the intracranial hemodynamic ada ptive status of the patient. Particular attention should be paid to cerebro vascular reactivity and the number and type of collateral Vessels that are present.