EXPERIMENTAL STUDY OF AORTIC BMHV FLOW CHARACTERISTICS UNDER DIFFERENT PHYSIOLOGICAL CONDITIONS USING PIV

Prosthetic heart valve (PHV) replacement for diseased native valves stands as the primary therapeutic modality for valvular heart diseases. Bileaflet mechanical heart valves (BMHV) are extensively employed in clinical practice due to their commendable durability. Post-valve replacement, complications such as thromboembolism emerge, intricately linked to alterations in the physiological blood flow pattern induced by the structural changes in mechanical valves. In this study, a physiologically pulsatile left heart flow circulation system was constructed. A realistic human aortic root silicone model, derived from medical CT images, was utilized, and a transparent chamber with adjustable pressure housed the aortic root model to simulate the impact of arterial compliance on blood flow. Simulating inlet and outlet loading conditions under varying physiological pressures and flow rates corresponding to healthy, heart failure, and exercise states, Particle Image Velocimetry (PIV) technology was employed to capture planar flow field data throughout a complete cardiac cycle as blood passed through a bileaflet mechanical valve in the aortic root. Velocity distribution, vorticity distribution, and shear stress analysis were conducted to assess the blood flow characteristics of the bileaflet mechanical valve at the aortic root, sinus, and ascending aorta. The study investigated the influence of different physiological states on transvalvular blood flow, providing theoretical foundations and experimental data support for preoperative valve selection and postoperative patient rehabilitation. Results revealed that, under exercise conditions with an elevated cardiac output ( CO= 14.6 L/min), blood exhibited a peak velocity of 2.2 m/s, impacting the wall at the junction of the aortic sinus and ascending aorta. The wall experienced a maximum shear stress of 2.8 N/m ², surpassing 1.4 N/m ²throughout the entire systolic phase, potentially leading to the exposure of collagen and tissue factor in the flowing blood, triggering platelet activation. Hence, postoperative patients are advised to avoid prolonged periods of physical activity to mitigate the risk of hemolysis-induced thromboembolism.