Impaired Cerebral Hemodynamics in Internal Carotid Occlusion

Abstract

We performed a hemodynamic assessment involving the measurement of regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) with single-photon-emitting isotopes in 75 patients with unilateral or bilateral carotid occlusions. rCBF was measured by following the clearance of inhaled ¹³³Xe and rCBV by single-photon emission tomographic recording of the distribution of ^99mTc-labeled autologous erythrocytes. Four patterns were observed, one of which appears to represent a state of hemodynamic compromise associated with an impaired hemodynamic reserve (HR) manifesting as compensatory vasodilation and impaired autoregulation to changes in PACO2. Impaired hemodynamics were noted in 27% of patients and in 35% of the 51 patients that would have been ''eligible'' for randomization in the extracranial-intracranial (ECIC) bypass study of Barnett et al. [Surg Neurol 1986;26:222–226]. Thirty-three patients thus ''eligible'' had normal HR and only 1 suffered a delayed stroke ipsilateral to an occluded artery in 21 months of follow-up. Eighteen ''eligible'' patients with impaired HR were also followed during a mean of 21 months. Fourteen of the patients with impaired HR underwent ECIC bypass and suffered a high (18%) perioperative morbidity and mortality; 4 were not operated upon, and 2 of these developed hemiplegia due to infarction ipsilateral to the ICA occlusion. We conclude that relatively few patients considered suitable for ECIC bypass on clinical and radiological grounds have an impaired HR which might justify revascularization. The clinical benefit of revascularization in those selected because of impaired hemodynamics remains to be demonstrated. In this context it appears from our small series that there is a high risk for surgery as well as spontaneous stroke in this population.