Effect of Adenosine on Cerebral Blood Flow as Evaluated by Single-Photon Emission Computed Tomography in Normal Subjects and in Patients With Occlusive Carotid Disease

Abstract

Acetazolamide is commonly used with single-photon CT to assess the cerebrovascular reserve in patients with internal carotid artery stenosis or occlusion. In this study we wanted to evaluate the effects of adenosine, a well-known vasodilatatory compound with a short biological half-life, on brain circulation in humans and compare the results with those of acetazolamide. Acetazolamide (1 g) and adenosine (140 micrograms/kg per minute) were injected intravenously on different days in 6 normal subjects and 6 patients: 4 with unilateral stenosis, 1 with bilateral stenosis, and 1 with complete occlusion of the internal carotid artery. Changes in regional cerebral blood flow relative to that of the cerebellum (cortico/cerebellar ratios) from resting conditions were evaluated by 99mTc-hexamethylpropyleneamine oxime and single-photon emission CT. The measured blood flow ratios increased significantly in the normal group 20 minutes after acetazolamide injection in several cortical and subcortical regions, as well as at the 4th minute of a 6-minute adenosine infusion. Regional cerebral blood flow ratio values were higher after adenosine than after acetazolamide in both cortical (frontal and parietal) and subcortical (thalamus and basal ganglia) regions. In 4 of the 6 patients the side-to-side asymmetry increased from the basal resting condition after the injection of acetazolamide and even more so after the injection of adenosine. Adenosine infusion causes vasodilation of cerebral arteries and can be used for the investigation of cerebrovascular perfusion capacity in patients with carotid occlusive disease. One advantage in the use of adenosine over acetazolamide is the possibility of interrupting the test with reversal of clinical symptoms or patient discomfort within a few minutes.