THE EFFECT OF ARM EXERCISE ON REGIONAL CEREBRAL BLOOD-FLOW IN THE SUBCLAVIAN STEAL SYNDROME

Reversed vertebral blood flow distal to a subclavian obstruction is no t uncommon and rarely leads to stroke. A small subgroup of these patie nts have obstruction in other portions of the extracranial or intracra nial circulation, however, and cerebrovascular symtoms are induced by arm exercise, which may decrease regional cerebral blood flow-at times to critical levels-indicating a true ''steal'' syndrome. We evaluated six patients with symptomatic subclavian steal syndrome using stable xenon with computed tomography cerebral blood flow mapping. A decrease in flow from 13% to 90% in one or more regional vascular territories nas found after arm exercise. Patients with a true ''steal'' syndrome may he at higher risk for stroke. Measuring regional cerebral blood fl ow may be a means of detecting patients who have a critical loss of fl ow reserves and who will be symptomatically improved by cerebral revas cularization.