The normal healthy aortic valve (AoV) has three leaflets, two of which have outflows to the coronary arteries. Blood flow through the coronary ostia will have an impact on AoV dynamics and the surrounding haemodynamics, leading to differential shear stress distributions at the aortic side of the three leaflets. In addition, aortic root haemodynamics may also be influenced by the non-Newtonian behaviour of blood which is known as a shear-thinning fluid due to the aggregation of red blood cells at low shear rate. However, the combined effect of coronary and non-Newtonian flow on AoV haemodynamics has not been studied in an anatomically realistic setting. In this study, strongly coupled fluid–structure interaction (FSI) analyses were performed on a natural, healthy AoV, with and without accounting for coronary outflows and non-Newtonian properties of blood. Our results showed that the influence of coronary outflow is more pronounced than employing a non-Newtonian model, and their combined effect is non-negligible, particularly on wall shear stress. Incorporating coronary outflow and non-Newtonian properties increased time-averaged wall shear stress (TAWSS) in the aortic sinus by up to 108.45%; it also increased TAWSS on the aortic side of valve leaflets by 41.04%, 44.76%, and 54.91% on the left, right and non-coronary leaflet, respectively. These results highlight the importance of incorporating coronary outflow and non-Newtonian properties when accurate predictions of wall shear stress and its related parameters are critical.

Background: Bioprosthetic aortic valves (BPAV) have been increasingly used for surgical aortic valve replacement (SAVR), but long-term complications associated with structural valve deterioration remain a concern. The structural behaviour of the valve and its surrounding haemodynamics play a key role in the long-term outcome of SAVR, and these can be quantitively analysed by means of fluid-structure interaction (FSI) simulation. The aim of this study was to develop a fully coupled FSI model for patient-specific analysis of BPAV haemodynamics. Methods: Using the Edwards Magna Ease valve as an example, the workflow included reconstruction of the aortic root from CT images and the creation of valve geometric model based on available measurements made on the device. Two-way fully coupled FSI simulations were performed under patient-specific flow conditions derived from 4D flow magnetic resonance imaging (MRI), the latter also provided data for model validation. Results: The simulation results were in good agreement with haemodynamic features extracted from 4D flow MRI and relevant data in the literature. Furthermore, the FSI model provided additional information that cannot be measured in vivo, including wall shear stress and its derivatives on the valve leaflets and in the aortic root. Conclusion: The FSI workflow presented in this study offers a promising tool for patient-specific assessment of aortic valve haemodynamics, and the results may help elucidate the role of haemodynamics in structural valve deterioration.

The opening and closing dynamics of the aortic valve (AV) has a strong influence on haemodynamics in the aortic root, and both play a pivotal role in maintaining normal physiological functions of the valve. The aim of this study was to establish a subject-specific fluid–structure interaction (FSI) workflow capable of simulating the motion of a tricuspid healthy valve and the surrounding haemodynamics under physiologically realistic conditions. A subject-specific aortic root was reconstructed from magnetic resonance (MR) images acquired from a healthy volunteer, whilst the valve leaflets were built using a parametric model fitted to the subject-specific aortic root geometry. The material behaviour of the leaflets was described using the isotropic hyperelastic Ogden model, and subject-specific boundary conditions were derived from 4D-flow MR imaging (4D-MRI). Strongly coupled FSI simulations were performed using a finite volume-based boundary conforming method implemented in FlowVision. Our FSI model was able to simulate the opening and closing of the AV throughout the entire cardiac cycle. Comparisons of simulation results with 4D-MRI showed a good agreement in key haemodynamic parameters, with stroke volume differing by 7.5% and the maximum jet velocity differing by less than 1%. Detailed analysis of wall shear stress (WSS) on the leaflets revealed much higher WSS on the ventricular side than the aortic side and different spatial patterns amongst the three leaflets.