Abstract
Objective: Hypertension is associated with reduced cerebral blood flow, but it is not known how this impacts on wave dynamics or potentially relates to arterial morphology. Given the location of the internal carotid artery (ICA) and risks associated with invasive measurements, wave dynamics in this artery have not been extensively assessed in vivo. This study explores the feasibility of studying wave dynamics in the internal carotid artery non-invasively. Approach: Normotensive, uncontrolled and controlled hypertensive participants were recruited (daytime ambulatory blood pressure <135/85 mmHg and >135/85 mmHg, respectively; n = 38). Wave intensity, reservoir pressure and statistical shape analyses were performed on the right ICA and ascending aorta high-resolution phase-contrast magnetic resonance angiography data. Main results: Wave speed in the aorta was significantly lower in normotensive compared to hypertensive participants (6.7 ± 1.8 versus 11.2 ± 6.2 m s−1 for uncontrolled and 11.8 ± 4.6 m s−1 for controlled hypertensives, p = 0.02), whilst there were no differences in wave speed in the ICA. There were no significant differences between the groups for the wave intensity or reservoir pressure. Interestingly, a significant association between the anatomy of the ICA and wave energy (FCW and size, r2 = 0.12, p = 0.04) was found. Significance: This study shows it is feasible to study wave dynamics in the ICA non-invasively. Whilst changes in aortic wave speed confirmed an expected increase in arterial stiffness, this was not observed in the ICA. This might suggest a protective mechanism in the cerebral circulation, in conjunction with the effect of vessel tortuosity. Furthermore, it was observed that ICA shape correlated with wave energy but not wave speed.
Highlights
Arterial wave transmission is of great interest to better understand integrated cardiovascular physiology
Wave speed Wave speed in the aorta was significantly lower in the normotensive group (6.7 ± 1.8 m s−1, analysis of variance (ANOVA) p = 0.0197, see figure 2(A)) compared to both the uncontrolled (11.8 ± 4.6 m s−1, p = 0.02 Dunnett post hoc) and controlled hypertensive (11.2 ± 6.2 m s−1, p = 0.04 Dunnett post hoc)
Wave speed in the aorta was positively correlated with ambulatory daytime pulse pressure (r = 0.3, r2 = 0.09, p = 0.04, figure 2(B)) and systolic blood pressure (r = 0.4, r2 = 0.2, p = 0.01, figure 2(C)), this correlation was not present in the internal carotid artery (ICA) (figures 2(E) and (F))
Summary
Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. S Neumann1 , F Sophocleous1, M D Kobetic1, E C Hart1, A K Nightingale1,2, K H Parker3, M K Hamilton2 and G Biglino1,2 Keywords: wave intensity analysis, reservoir pressure, statistical shape modelling, internal carotid artery, blood pressure, hypertension Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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