Fluid-structure simulations outperform computational fluid dynamics in the differentiation of progressive dilation in Marfan syndrome patients

Introduction: 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 4D-flow MRI data; and to assess the
capacity of advanced fluid dynamics markers to stratify aneurysm
progression risk. Methods: Eight Marfan syndrome 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, was evaluated from FSI and CFD simulations and
assessed as potential correlate of aneurysm progression. Results: 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 shear stress ratio differentiated
between stable and dilating Marfan patients. Conclusions: Fluid dynamic
simulations of the thoracic aorta require fluid-solid interaction to
properly reproduce complex hemodynamics. FSI- but not CFD-derived shear
stress ratio could help stratifying Marfan patients.