Assessment of Cerebral Vasomotor Reactivity by Transcranial Doppler Ultrasound and Breath-Holding

Abstract

BACKGROUND AND PURPOSE: Evaluating cerebrovascular vasomotor reactivity seems to be of prognostic relevance for patients with occlusive internal carotid artery disease. To evaluate its clinical usefulness, the recently introduced breath-holding maneuver as a carbon dioxide-dependent 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 arteries of 74 patients (mean +/- SD age, 62 +/- 9 years) with unilateral or bilateral occlusive carotid artery disease, vasomotor reactivity was estimated by the increase of middle cerebral artery mean blood velocity by transcranial Doppler ultrasound, comparing the breath-holding maneuver 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 additionally underwent stable xenon-enhanced computed tomography to calculate the increase of mean cortical regional cerebral blood flow in the middle cerebral artery territory after acetazolamide stimulation. RESULTS: The percentage of mean regional cerebral blood flow changes (n = 36 hemispheres) correlated best with the absolute mean blood velocity changes while breath-holding (P = .007, r = .4332). The absolute mean regional cerebral blood flow changes correlated best with the percentage of mean blood velocity changes after acetazolamide stimulation (P = .004, r = .4580). On all 134 middle cerebral arteries, both vasodilatory stimuli correlated highly significantly (P < .0001) when comparing increases in absolute (r = .5448) or relative (r = .3516) mean blood velocity. Both stimulation techniques similarly indicated significantly reduced vasomotor reactivity with increasing degree of internal carotid artery lesions (P < or = .01). However, the acetazolamide challenge differentiated 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 changes even when different vasodilatory stimuli are used. In cooperative patients the breath-holding maneuver as vasodilatory stimulus seems clinically useful for a first estimation of cerebral vasomotor reactivity.