Relationship between cerebral circulatory reserve and oxygen extraction fraction in patients with major cerebral artery occlusive disease: A positron emission tomography study

Abstract

Background and Purpose - The present study examined the relationship between circulatory and metabolic reserve in patients with hemodynamic impairment. Methods - Positron emission tomography was used to investigate 40 patients with major cerebral artery occlusive disease. The ratio of cerebral blood volume to cerebral blood flow (CBV/CBF) and vasoreactivity in response to hypercapnia (%CBFhypercapnia) and acetazolamide (ACZ) stress (%CBFACZ) were measured to evaluate circulatory reserve. Oxygen extraction fraction (OEF) was measured to evaluate metabolic reserve. To detect relationships between circulation reserve and OEF, cerebral hemispheres were grouped into 5 or 6 stepwise groups based on reduction of circulation reserve. Results - OEF was significantly elevated in hemispheres with CBV/CBF ≥0.11 minutes and in hemispheres with %CBFhypercapnia <0%. OEF was significantly increased according to %CBFACZ in hemispheres with %CBFACZ <15% and plateaued at levels below -15%. Conclusions - Metabolic reserve consumption began at CBV/CBF ≥0.11 minutes, CBF hypercapnia <0%, and CBFACZ <15%. © 2006 American Heart Association, Inc.