Abstract
Abnormal fluid dynamics at the ascending aorta may be at the origin of aortic aneurysms. This study was aimed at comparing the performance of computational fluid dynamics (CFD) and fluid–structure interaction (FSI) simulations against four-dimensional (4D) flow magnetic resonance imaging (MRI) data; and to assess the capacity of advanced fluid dynamics markers to stratify aneurysm progression risk. Eight Marfan syndrome (MFS) patients, four with stable and four with dilating aneurysms of the proximal aorta, and four healthy controls were studied. FSI and CFD simulations were performed with MRI-derived geometry, inlet velocity field and Young's modulus. Flow displacement, jet angle and maximum velocity evaluated from FSI and CFD simulations were compared to 4D flow MRI data. A dimensionless parameter, the shear stress ratio (SSR), was evaluated from FSI and CFD simulations and assessed as potential correlate of aneurysm progression. FSI simulations successfully matched MRI data regarding descending to ascending aorta flow rates (R2 = 0.92) and pulse wave velocity (R2 = 0.99). Compared to CFD, FSI simulations showed significantly lower percentage errors in ascending and descending aorta in flow displacement (−46% ascending, −41% descending), jet angle (−28% ascending, −50% descending) and maximum velocity (−37% ascending, −34% descending) with respect to 4D flow MRI. FSI- but not CFD-derived SSR differentiated between stable and dilating MFS patients. Fluid dynamic simulations of the thoracic aorta require fluid–solid interaction to properly reproduce complex haemodynamics. FSI- but not CFD-derived SSR could help stratifying MFS patients.
Highlights
Thoracic aortic aneurysms are normally associated with conditions such as hypertension, ageing or genetic abnormalities, like Marfan syndrome (MFS) [1]
2 jet angle and maximum velocity evaluated from fluid–structure interaction (FSI) and computational fluid dynamics (CFD) simulations were compared to 4D flow magnetic resonance imaging (MRI) data
The main objectives of this work are (i) to study the accuracy of CFD and FSI simulations compared to 4D flow MRI data in MFS patients with a thoracic aorta aneurysm, and (ii) to compare advanced fluid dynamics markers between derived by CFD versus FSI simulations and assess their capacity to stratify the risk of aneurysm progression
Summary
Thoracic aortic aneurysms are normally associated with conditions such as hypertension, ageing or genetic abnormalities, like Marfan syndrome (MFS) [1]. The maximum aortic diameter is the main parameter used for the assessment of rupture risk. Surgical intervention is indicated for ascending aorta aneurysms with diameters larger than 50 mm in MFS patients [3,4] or 55 mm in nongenetic aortic aneurysms. Multimodality imaging has agreement and reproducibility limitations [6]. In this context, the use of biomechanical markers, such as aortic wall shear stress (WSS), stiffness and strain, is gaining a prominent role in the quest of possible factors for improving patient stratification [7,8,9,10,11]. To date, biomechanical markers have not been included in clinical practice
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