St. Louis, Sept. 23, 1998--By measuring oxygen use in the brain, researchers at Washington University School of Medicine in St. Louis can determine which patients with blocked carotid arteries are at high risk for a stroke.
The findings, reported in the Sept. 23/30, 1998 issue of the Journal of the American Medical Association, could have implications for reviving a discarded surgical procedure that increases blood flow to the brain.
Robert L. Grubb Jr., M.D., William J. Powers, M.D., and colleagues report that patients with complete blockage of the carotid artery and a condition called hemodynamic failure, face a stroke risk six to seven times greater than those with just a blocked carotid artery. Hemodynamic failure occurs when the brain is not receiving the normal amount of oxygenated blood.
Using a specialized imaging test called positron emission tomography (PET), the investigators measured both blood flow and oxygen metabolism in the brains of the study subjects. They studied 81 patients over four years. All had complete blockage of one of their carotid arteries and had suffered either a stroke or a transient ischemic attack, which has similar symptoms to stroke but resolves itself in a few hours. The PET scans allowed the researchers to determine whether patients were in hemodynamic failure by revealing the amount of blood that reached the brain and the percentage of oxygen that the brain used.
"Under normal circumstances, the amount of blood that gets to the brain and the amount of oxygen the brain extracts from the blood are pretty well matched," said Powers, a professor of neurology and associate professor of radiology at the School of Medicine. "But using PET, we confirmed that in some patients with blocked carotid arteries, there was an imbalance between blood supply and the amount of oxygen used by the part of the brain supplied by the blocked vessel."