283Morphometric analysis of internal carotid arteries in hypertensives implementing a semi-automatic measurement platform for magnetic resonance imaging data

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Introduction Despite extensive cardiovascular remodelling and other severe consequences occurring with long standing hypertension, the mechanisms underpinning its development remain unclear. Evidence from animal and ex-vivo studies support the hypothesis that high blood pressure (BP) may protect the brain when blood supply is inadequate. Recently, it has been shown that hypertensive patients are more likely to have hypoplastic or missing vertebral or posterior cerebral arteries, which are associated with increased cerebrovascular resistance and reduced cerebral perfusion. Although the internal carotid arteries (ICA) supply oxygenated blood to a large portion of the brain, a possible relationship between their morphology and hypertension has not been adequately investigated. Purpose To assess the influence of ICA morphometry on arterial flow and cerebral perfusion, and investigate their relation with hypertension. Methods We reconstructed the anatomy of the right and left ICA from 3D Time of Flight angiograms of normotensive and hypertensive subjects (n = 112). Each model was cut between the anterior communicating artery and the end of the carotid canal, then subdivided into 6 anatomical tracts according to the bending of the vessel. We implemented a semi-automatic platform (Matlab) that automatically identifies the tracts and measures the correspondent tortuositites (distance factor metric), lengths, curvatures and cross-sectional areas. We then integrated morphometric, demographic and clinical data of pressure and flow from phase-contrast pulse sequences and carried out a statistical analysis. An unpaired Student t-test was used to test for differences between normotensive and hypertensive groups, while a Dunn’s test was used among subgroups in relation to the action of antihypertensive medications. Results Compared to normotensives, treated hypertensives had normalised ambulatory BP but reduced total ICA flow (p < 0.007), while untreated hypertensives had higher BP but similar blood flow (p = 0.05). The flow reduction in the treated was not related to hypoplastic ICA or local lumen narrowing. Global and local tortuositites of the right and left ICA did not differ between normotensives and hypertensives. Overall, morphometric features were not associated with ICA flow and hypertension in the studied population. However, treated hypertensives exhibited more tortuous vessels than untreated (p = 0.028) and borderline (p= 0.045) patients. Locally, the carotid siphon in the untreated hypertensives was less tortuous (p = 0.027) and curved (p = 0.018) compared to normotensives, suggesting some degree of geometric remodelling of the vessels depending on the stage of hypertension. Conclusions The developed platform allows automatising and standardising the measurement of detailed morphological features of the ICA. The morphology of the ICA, especially around the carotid siphon, may remodel during different stages of hypertension. Abstract 283 Figure. Carotid curvature and subdivision.

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