The structure of atherosclerotic plaque as a defining factor of cerebrovascular reactivity in patients with carotid atherosclerosis

The aim of our study was to compare the magnetic resonance imaging (MRI)-based structure of atherosclerotic plaques and cerebral vascular reactivity quantified by echocardiography. All patients underwent MRI of the carotid arteries. To assess the cerebrovascular reactivity, transcranial ultrasound of middle cerebral artery was carried out with quantification of blood flow parameters at rest and during stress tests: first with breath holding and then with hyperventilation, with calculation of reactivity index. Data showed a statistically significant association between MRI plaque structure and type of the reaction during breath holding in hypercapnic test, whereas no significant differences were found in hyperventilation test. In breath-holding test, 56% of patients with hypointense plaques on T1- and hyperintense plaques on T2-weighted MRI scans had unidirectional positive response to functional hypercapnic stress. On the contrary, pathologic unidirectional negative or negative response on a side of the stenosis was observed in patients with MRI evidence of hyperintense plaques on T1- and hypointense plaques on T2-weighted scans. Atherosclerotic lesions of the internal carotid artery with intra-plaque hemorrhage were accompanied with critical deterioration of cerebrovascular reactivity. Any hemorrhage to carotid plaque could probably be assumed as critical risk factor requiring removal of the plaque by carotid endarterectomy. High-resolution MRI of carotid arteries may be suggested as screening test for all patients in atherosclerosis risk groups.