Effect of collateral blood flew and cerebral vasomotor reactivity on the outcome of carotid artery occlusion

Background and Purpose-Evidence suggests that an alteration in cerebral hem odynamics plays a relevant role in the occurrence of stroke in patients wit h carotid occlusion. The purpose of the present study was to evaluate the r elationships among baseline characteristics, type and number of collateral pathways, cerebral vasomotor reactivity (VMR), and outcome of patients with carotid occlusion, Methods-One hundred four patients with symptomatic or asymptomatic internal carotid artery occlusion were followed up prospectively for a median perio d of 24 months, Cerebral VMR to apnea was calculated with transcranial Dopp ler ultrasonography by means of the breath-holding index (BHI) in the middl e cerebral arteries. The patency of the 3 major intracranial collateral ves sels was also evaluated. Results-During the follow-up period, 18 patients experienced an ischemic st roke ipsilateral to internal carotid artery occlusion, Among factors consid ered, only older age, number of collateral pathways, and BHI values in the middle cerebral artery ipsilateral to the occluded side were significantly associated with the risk of ipsilateral stroke: (P <0.001, P=0.008 and P <0 .001, respectively; multiple Cox regression analysis). A normal VMR and fav orable prognosis characterized patients with full collateral development; i n this group, no patient experienced an ischemic event. On the other hand, an impaired VMR and increased probability of experiencing a stroke were fou nd in patients without collateral pathways; the annual risk of ipsilateral stroke in this group was 32.7%. Patients with 1 or 2 collateral pathways sh owed a different VMR ranging from normal to strongly reduced BHI values. Th e ipsilateral stroke event-risk was 17.5% in patients with 1 collateral ves sel and 2.7% in patients with 2 collateral pathways. In this case, the risk of cerebrovascular events occurring during the follow-up period was signif icantly related to VMR. Conclusions-These data suggest that cerebral hemodynamic status in patients with carotid occlusive disease is influenced by both individual anatomic a nd functional characteristics. The planning of strategies to define the:ris k profile: and any attempt to influence patients' outcome should be based o n the evaluation of the intracranial hemodynamic adaptive status, with part icular attention to the number of collateral vessels and the related VMR.