PIV EXPERIMENTAL STUDY ON THE FLOW FIELD CHARACTERISTICS OF AORTIC VALVE WITH ECCENTRIC LOWER VALVE PLACEMENT
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Abstract:
Purpose Investigating the impact of eccentric positioning for various types of artificial aortic valves on downstream flow dynamics. Methods This study employed a physiological pulsatile circulation simulation system and utilized Particle Image Velocimetry (PIV) to analyze the downstream flow field variations for bioprosthetic and mechanical valves under two positioning conditions: centralized placement (0 mm) and eccentric placement (1 mm). Hemodynamic parameters such as velocity, vorticity, and viscous shear stress were assessed to evaluate the flow field characteristics. Results By analyzing the flow field variations at four characteristic time points—early systole, acceleration phase, peak systole, and deceleration phase—significant differences in flow field distribution between bioprosthetic and mechanical valves were observed. The bioprosthetic valve exhibited a centrally symmetric jet with higher flow velocity, whereas the mechanical valve displayed a three-jet structure with lower central flow velocity. Under eccentric placement, the blood flow in the aortic sinus region was sluggish, with a reduction in average velocity, hindering the formation and maintenance of vortices. During the peak systolic phase, the maximum viscous shear stresses in the sinus region for the bioprosthetic and mechanical valves were 0.45 N/m2 and 0.67 N/m2, respectively, approaching the threshold for endothelial cell damage. Conclusions Eccentric placement of both mechanical and bioprosthetic valves resulted in reduced sinus blood flow velocity and diminished viscous shear stress, creating favorable conditions for thrombus formation. Clinical valve replacement procedures should prioritize optimal positioning to avoid eccentric placement and associated complications.
