Cerebral blood flow pattern in patients with carotid artery stenosis with low trans-stenotic blood flow

BackgroundCompromised cerebral blood flow has been identified as a contributing risk factor for future ischemic events in patients with symptomatic carotid artery disease. Nevertheless, the hemodynamic impact of carotid stenosis is rarely evaluated. The aim of this observational cross-section study was to investigate how a reduced internal carotid artery (ICA) blood flow rate (BFR), rather than stenosis degree, relates to BFR in the cerebral arteries. MethodsFour-dimensional phase-contrast magnetic resonance imaging (4D-PCMRI) was used to measure cerebral blood flow in 38 patients with symptomatic carotid stenosis ([&ge;]50%), being considered for carotid endarterectomy. The BFR in the cerebral arteries was compared between two subgroups that were based on the BFR in the symptomatic (ipsilateral) ICA: I. reduced ICA flow (<160 mL/min) i.e., 2 SD <normal ICA BFR; II. preserved ICA flow ([&ge;]160 mL/min). Furthermore, BFR laterality was defined as a difference in the paired ipsilateral-contralateral arteries within the groups. ResultsThe degree of stenosis was not significantly different between the two subgroups (72% vs. 80%; P=0.09). In the reduced group compared to the preserved ICA flow group, a reduced BFR was found in the ipsilateral middle cerebral artery (MCA) (108{+/-}32 vs. 136{+/-}24 mL/min; P<0.01) and anterior cerebral artery (A1 segment) (-6{+/-}47 vs. 81{+/-}27 mL/min; P<0.001), while the BFR was increased in the contralateral A1 segment (152{+/-}79 vs. 82{+/-}41 mL/min; P<0.001). There was also a reversed BFR in the posterior communicating artery and ophthalmic artery on the ipsilateral side in the group with reduced ICA flow. BFR laterality was observed in all paired arteries in the reduced ICA flow group (P<0.05), while there was no laterality in the preserved ICA flow group (P>0.05). Conclusions4D-PCMRI revealed compromised cerebral blood flow in patients with carotid stenosis, not possible to detect by solely analyzing the stenosis degree. In patients with reduced ICA flow, collateral recruitment was not sufficient to maintain symmetrical BFR distribution to the two hemispheres.