ASSESSMENT OF CEREBRAL VASOMOTOR REACTIVITY BY TRANSCRANIAL DOPPLER ULTRASOUND AND BREATH-HOLDING - A COMPARISON WITH ACETAZOLAMIDE AS VASODILATORY STIMULUS

Background and Purpose Evaluating cerebrovascular vasomotor reactivity seems to be of prognostic relevance for patients with occlusive inter nal carotid artery disease. To evaluate its clinical usefulness, the r ecently introduced breath-holding maneuver as a carbon dioxide-depende nt vasodilatory stimulus was compared with the acetazolamide challenge by means of transcranial Doppler ultrasound and stable xenon-enhanced computed tomography. Methods In a total of 134 middle cerebral arteri es of 74 patients (mean+/-SD age, 62+/-9 years) with unilateral or bil ateral occlusive carotid artery disease, vasomotor reactivity was esti mated by the increase of middle cerebral artery mean blood velocity by transcranial Doppler ultrasound, comparing the breath-holding maneuve r and 1 g IV acetazolamide as vasodilatory stimuli. The carotid artery findings were classified as normal, stenosis of 50% to <70%, 70% to < 90%, 90% to 99%, and occlusion. Eighteen of the 74 patients additional ly underwent stable xenon-enhanced computed tomography to calculate th e increase of mean cortical regional cerebral blood flow in the middle cerebral artery territory after acetazolamide stimulation. Results Th e percentage of mean regional cerebral blood how changes (n=36 hemisph eres) correlated best with the absolute mean brood velocity changes wh ile breath-holding (P=.007, r=.4332). The absolute mean regional cereb ral blood flow changes correlated best with the percentage of mean blo od velocity changes after acetazolamide stimulation (P=.004, r=.4580). On all 134 middle cerebral arteries, both vasodilatory stimuli correl ated highly significantly (P<.0001) when comparing increases in absolu te (r=.5448) or relative (r=.3516) mean blood velocity. Both stimulati on techniques similarly indicated significantly reduced vasomotor reac tivity with increasing degree of internal carotid artery lesions (P le ss than or equal to.01). However, the acetazolamide challenge differen tiated more accurately between the various groups of internal carotid artery findings. Conclusions The assessment of vasomotor reactivity by transcranial Doppler ultrasound correlates with cerebral blood flow c hanges even when different vasodilatory stimuli are used. In cooperati ve patients the breath-holding maneuver as vasodilatory stimulus seems clinically useful for a first estimation of cerebral vasomotor reacti vity.