Hemodynamic Abnormalities in the Aorta of Turner Syndrome Girls.

Lauren Johnston,Asimina Kazakidi,Avril Mason,Ruth Allen,Pauline Hall Barrientos

doi:10.3389/fcvm.2021.670841

Abstract

Congenital abnormalities in girls and women with Turner syndrome (TS), alongside an underlying predisposition to obesity and hypertension, contribute to an increased risk of cardiovascular disease and ultimately reduced life expectancy. We observe that children with TS present a greater variance in aortic arch morphology than their healthy counterparts, and hypothesize that their hemodynamics is also different. In this study, computational fluid dynamic (CFD) simulations were performed for four TS girls, and three age-matched healthy girls, using patient-specific inlet boundary conditions, obtained from phase-contrast MRI data. The visualization of multidirectional blood flow revealed an increase in vortical flow in the arch, supra-aortic vessels, and descending aorta, and a correlation between the presence of aortic abnormalities and disturbed flow. Compared to the relatively homogeneous pattern of time-averaged wall shear stress (TAWSS) on the healthy aortae, a highly heterogeneous distribution with elevated TAWSS values was observed in the TS geometries. Visualization of further shear stress parameters, such as oscillatory shear index (OSI), normalized relative residence time (RRTn), and transverse WSS (transWSS), revealed dissimilar heterogeneity in the oscillatory and multidirectional nature of the aortic flow. Taking into account the young age of our TS cohort (average age 13 ± 2 years) and their obesity level (75% were obese or overweight), which is believed to accelerate the initiation and progression of endothelial dysfunction, these findings may be an indication of atherosclerotic disease manifesting earlier in life in TS patients. Age, obesity and aortic morphology may, therefore, play a key role in assessing cardiovascular risk in TS children.

Highlights

Turner syndrome (TS) is a rare genetic disorder where the second sex chromosome in females is partially or completely absent and can affect all or only a percentage of cells
In all three healthy cases (H1-H3), the flow at peak systole was laminar throughout the aortic arch, the descending aorta, and the three major branches arising from the arch
The visualization of multidirectional blood flow revealed increased vortical flow in the arch, supraaortic branches, and descending aorta of the TS girls compared to the healthy controls, but no significant difference was found in the ascending aorta

Summary

Introduction

Turner syndrome (TS) is a rare genetic disorder where the second sex chromosome in females is partially or completely absent and can affect all or only a percentage of cells (mosaicism). The clinical characteristics of TS are highly variable, with congenital heart abnormalities estimated to occur in as many as half of individuals [4] These defects predominantly affect the left side of the heart, with the most commonly reported being an elongated transverse aortic arch (ETA) [5, 6]. Aberrant right subclavian artery (RSA) is an anatomical variation of the RSA which atypically originates from the arch as a separate fourth branch and has a prevalence of 8% in TS [6] These congenital abnormalities, alongside an underlying predisposition to obesity and hypertension, contribute to a greater risk of cardiovascular disease and reduced life expectancy in TS [9]

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Discussion

Conclusion