On the impact of vessel wall stiffness on quantitative flow dynamics in a synthetic model of the thoracic aorta

Judith Zimmermann,Kyle Gifford,Seraina A Dual,Marc Levenston,Daniel B Ennis,Fikunwa O Kolawole,Michael Loecher,Kathrin Bäumler,Alison L Marsden

doi:10.1038/s41598-021-86174-6

Abstract

Aortic wall stiffening is a predictive marker for morbidity in hypertensive patients. Arterial pulse wave velocity (PWV) correlates with the level of stiffness and can be derived using non-invasive 4D-flow magnetic resonance imaging (MRI). The objectives of this study were twofold: to develop subject-specific thoracic aorta models embedded into an MRI-compatible flow circuit operating under controlled physiological conditions; and to evaluate how a range of aortic wall stiffness impacts 4D-flow-based quantification of hemodynamics, particularly PWV. Three aorta models were 3D-printed using a novel photopolymer material at two compliant and one nearly rigid stiffnesses and characterized via tensile testing. Luminal pressure and 4D-flow MRI data were acquired for each model and cross-sectional net flow, peak velocities, and PWV were measured. In addition, the confounding effect of temporal resolution on all metrics was evaluated. Stiffer models resulted in increased systolic pressures (112, 116, and 133 mmHg), variations in velocity patterns, and increased peak velocities, peak flow rate, and PWV (5.8–7.3 m/s). Lower temporal resolution (20 ms down to 62.5 ms per image frame) impacted estimates of peak velocity and PWV (7.31 down to 4.77 m/s). Using compliant aorta models is essential to produce realistic flow dynamics and conditions that recapitulated in vivo hemodynamics.

Highlights

Aortic wall stiffening is a predictive marker for morbidity in hypertensive patients
Aortic wall stiffening is linked to an increase of pulse wave velocity (PWV) - the velocity at which the blood pressure pulse travels through the circulatory system
Non-invasive 4D-flow magnetic resonance imaging (MRI) provides three-dimensional (3D) and timeresolved velocity vector maps that serve as basis for image-based quantitative flow c haracterization[7,8]

Summary

Introduction

Aortic wall stiffening is a predictive marker for morbidity in hypertensive patients. The objectives of this study were twofold: to develop subject-specific thoracic aorta models embedded into an MRI-compatible flow circuit operating under controlled physiological conditions; and to evaluate how a range of aortic wall stiffness impacts 4D-flow-based quantification of hemodynamics, PWV. In. particular, 4D-flow PWV calculations use a similar transit-time over fixed distance approach as in conventional cfPWV measurements, but in addition exploits the volumetric imaging d ata[9] and analyzes temporal shifts in flow rate waveforms extracted at numerous cross-sectional image planes along the aorta. Particular, 4D-flow PWV calculations use a similar transit-time over fixed distance approach as in conventional cfPWV measurements, but in addition exploits the volumetric imaging d ata[9] and analyzes temporal shifts in flow rate waveforms extracted at numerous cross-sectional image planes along the aorta This approach enables both regionally specific and more robust PWV estimates compared to two-point methods. The same studies affirm that PWV increases with age and in the presence of aortic atherosclerosis

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Conclusion