Assessment of cerebrovascular reserve capacity in asymptomatic and symptomatic hemodynamically significant carotid stenoses and occlusions

Abstract

BACKGROUND Cerebrovascular reactivity measurements are believed to be a helpful tool for selecting patients who are at higher risk for hemodynamic strokes. The aim of this study was to compare cerebral vasoreactivity among patients suffering from internal carotid artery stenosis of different severity (asymptomatic stenosis, asymptomatic occlusion, symptomatic stenosis, symptomatic occlusion). METHODS Sixty-two patients with asymptomatic and symptomatic internal carotid artery stenoses and occlusions underwent transcranial Doppler-acetazolamide tests. Absolute velocities of the middle cerebral arteries (MCAV), percent increases of the MCAV at different time points of the test (cerebrovascular reactivity, CVR) and maximal percent increase after administration of acetazolamide (cerebrovascular reserve, CRC) were compared on the affected and non-affected sides. Asymmetry indices (CRC affected side/CRC non-affected side) were compared between the groups of different severity of obstructive lesion. RESULTS Resting MCAV was similar on both sides in all groups. A significant side-difference of the MCAV values after acetazolamide was observed only in the symptomatic groups. Difference of cerebrovascular reserve capacity between the affected and non-affected side was statistically significant only in the symptomatic groups (CRC symptomatic stenosis 36.6 ± 20.9% vs. 71.1 ± 27.9%, CRC symptomatic occlusion: 31.2 ± 24.6% vs. 64.5 ± 29.7%). Asymmetry index of the CRC was near to 1 in the asymptomatic stenosis group only, while in all the other groups this index referred to a significant hemispheric asymmetry of the vasoreactivity. CONCLUSIONS Although in general cerebrovascular reserve capacity is compromised in cases of hemodynamically significant carotid lesions, there is a large individual variability within the subgroups. Further randomized studies are needed to clarify whether the clinical efficiency of carotid endarterectomy and extra-intracranial bypass may be improved by selecting the patients using hemodynamic criteria.