Increased Oxygen Extraction Fraction Is Associated With Prior Ischemic Events in Patients With Carotid Occlusion

Abstract

Background and Purpose —The purpose of our study was to investigate the relationship between misery perfusion (increased oxygen extraction fraction, OEF) and baseline risk factors in patients with carotid occlusion. Methods —One-hundred seventeen patients with atherosclerotic carotid occlusion were studied prospectively by clinical evaluation, laboratory testing, and positron emission tomography (PET). PET measurements of cerebral blood flow (CBF), cerebral blood volume (CBV), and OEF were made on enrollment in the study. Increased ipsilateral OEF was identified by comparison with 18 normal control subjects. Twenty-five baseline clinical, epidemiological, and arteriographic risk factors were assessed on study entry. Student t tests, χ 2 tests, and Fisher exact tests with Bonferroni correction were used to assess statistical significance ( P <.05). Results —Of 117 patients, 44 had increased OEF distal to the occluded carotid and 73 had normal OEFs. Thirty-nine of the 81 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 the two groups of patients. Conclusions —Investigations of the relationship between hemodynamic factors and stroke risk must take into account the lower frequency of hemodynamic abnormalities in asymptomatic patients.