INCREASED STROKE RISK PREDICTED BY COMPROMISED CEREBRAL BLOOD-FLOW REACTIVITY

The authors sought to determine risk for stroke in individuals with sy mptomatic carotid stenosis or occlusion based upon an assessment of ce rebral blood flow (CBF) reserves. Vascular reserve was assessed by two consecutive xenon/computerized tomography (Xe/CT) CBF studies with in travenous acetazolamide introduced 20 minutes prior to the second stud y. Patients were assigned t one of two vasoreactivity groups. Group 2 included individuals who experienced a CBF reduction of more than 5% i n at least one vascular territory and had a baseline flow of 45 cc/100 gm/min or less. Group 1 included all other individuals. Any territory with volume loss on CT of more than 50% was eliminated from analysis. Sixty-eight individuals were followed at 6-month intervals for a mean of 24 months. In Group 1 two strokes were observed contralateral to t he side with lowest reserve, for a stroke incidence of 4.4%; in Group 2 eight strokes were observed ipsilateral to the side with lowest rese rve, for a stroke incidence of 36%. The latter group had a 12.6 times greater chance of stroke (p = 0.0007). History of stroke, history of t ransient ischemic attacks, baseline CBF, and degree of stenosis were n ot associated with an increased stroke rate. In this study, significan tly compromised vascular reserves accompanied by relatively low initia l flow identified individuals who subsequently demonstrated a signific antly increased rate of ipsilateral stroke.