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 ≤.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.