INCREASED OXYGEN EXTRACTION FRACTION IS ASSOCIATED WITH PRIOR ISCHEMIC EVENTS IN PATIENTS WITH CAROTID OCCLUSION

Background and Purpose-The purpose of our study was to investigate the relationship between misery perfusion (increased oxygen extraction fr action, OEF) and baseline risk factors in patients with carotid occlus ion. Methods-One-hundred seventeen patients with atherosclerotic carot id occlusion were studied prospectively by clinical evaluation, labora tory testing, and positron emission tomography (PET). PET measurements of cerebral blood flow (CBF), cerebral blood volume (CBV), and OEF we re made on enrollment in the study, Increased ipsilateral OEF was iden tified by comparison with 18 normal control subjects, Twenty-five base line clinical, epidemiological, and arteriographic risk factors were a ssessed on study entry. Student t tests, chi(2) tests, and Fisher exac t tests with Bonferroni correction were used to assess statistical sig nificance (P<.05). Results-Of 117 patients, 44 had increased OEF dista l to the occluded carotid and 73 had normal OEFs. Thirty-nine of the 8 1 patients with prior ipsilateral ischemic symptoms had high OEFs (42% ), whereas only 5 of the 31 asymptomatic patients had high OEFs (16%, P<.001) All of the other baseline risk factors were similar between th e two groups of patients. Conclusions-Investigations of the relationsh ip between hemodynamic factors and stroke risk must take into account the lower frequency of hemodynamic abnormalities in asymptomatic patie nts.