The impact of coronary outflow and non-Newtonian fluid property on aortic valve haemodynamics.

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.