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 - A COMPARISON WITH ACETAZOLAMIDE

Background and Purpose Acetazolamide is commonly used with single-phot on CT to assess the cerebrovascular reserve in patients with internal carotid artery stenosis or occlusion. In this study we wanted to evalu ate the effects of adenosine, a well-known vasodilatatory compound wit h a short biological half-life, on brain circulation in humans and com pare the results with those of acetazolamide. Methods Acetazolamide (1 g) and adenosine (140 mu g/kg per minute) were injected intravenously on different days in 6 normal subjects and 6 patients: 4 with unilate ral stenosis, 1 with bilateral stenosis, and 1 with complete occlusion of the internal carotid artery. Changes in regional cerebral blood fl ow relative to that of the cerebellum (cortico/cerebellar ratios) from resting conditions were evaluated by Tc-99m-hexamethylpropyleneamine oxime and single-photon emission CT. Results The measured blood flow r atios increased significantly in the normal group 20 minutes after ace tazolamide injection in several cortical and subcortical regions, as w ell as at the 4th minute of a 6-minute adenosine infusion. Regional ce rebral 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 ad enosine. Conclusions Adenosine infusion causes vasodilatation of cereb ral arteries and can be used for the investigation of cerebrovascular perfusion capacity in patients with carotid occlusive disease. One adv antage in the use of adenosine over acetazolamide is the possibility o f interrupting the test with reversal of clinical symptoms or patient discomfort within a few minutes.