In vitro characterization of left ventricular flow dynamics in presence of a biological monoleaflet mitral valve prosthesis through Particle Image Velocimetry

Intraventricular flow patterns, pressure distribution, and kinetic energy are closely linked to left ventricular function. Mitral valve opening generates a large clockwise vortex in the left ventricle (LV), that promotes inflow, reduces energy loss, and directs flow towards the outflow tract. This study examines in vitro, using two-dimensional Particle Image Velocimetry (PIV), the fluid dynamics of the Epygon transcatheter mitral valve (Affluent Medical), designed with a pericardial monoleaflet, D-shaped annular ring, and self-expanding nitinol frame to restore physiological LV hemodynamics. Experiments were conducted using the ViVitro Pulse Duplicator System, a left heart simulator. The working fluid used was a 0.9% w/v NaCl solution with spherical polyamide tracer particles. Mitral flow was measured with an electromagnetic flowmeter, and pressure signals were recorded. The Epygon valve was placed in the mitral position, while in the aortic position a mechanical tilting disk valve (Vivitro Labs) and a biological trileaflets valve, the Perimount Magna Ease (Edwards Lifesciences Corporation), were tested to assess their impact on ventricular flow. The experiments followed BS EN ISO 5840-1:2021 standards (heart rate 70 bpm, systolic percentage 35%, and mean arterial pressure 100 mmHg) at cardiac outputs (CO) of 3.5, 5.0, and 5.5 L/min. A preliminary hydraulic characterization allowed the analysis of flow and pressure waveforms and calculation of Effective Orifice Area (EOA) and Regurgitation Fraction (RF). The images of the flow fields were acquired using a high-resolution sCMOS camera (Andor Zyla 5.5, Dantec Dynamics) in double-frame mode (2560 x 2160 pixels), synchronized with a dual-pulse Nd:YAG laser (532 nm). PIV measurements were conducted in phase-locked mode on 48 cardiac phases and on two orthogonal planes (xy and yz), enabling reconstruction of velocity fields and calculation of velocity magnitude, vorticity, circulation per unit area, turbulent kinetic energy (TKE), and shear rate. Velocity analysis revealed a laterally directed inflow jet during diastole, with maximum velocity increasing with CO, about 0.6 m/s at 3.5 L/min, 0.8 m/s at 5.0 L/min, and 0.9–1.0 m/s at 5.5 L/min. Vorticity fields revealed the development of a main clockwise sub valvular vortex, which expands, migrates toward the apex, and dissipates toward the end of diastole. With increasing CO, the vortex intensifies, reaching peak vorticity of −80 to −90 s⁻¹ at 3.5 L/min, around −100 s⁻¹ at 5.0 L/min, and −110 to −120 s⁻¹ at 5.5 L/min. Circulation per unit area followed a similar trend, becoming more negative during diastole as CO increased, reaching about −12 s⁻¹ at 5 L/min and gradually rising toward systole. Shear rate and TKE also rose with CO, with high-vorticity regions corresponding to TKE approximately 0.1 m²/s² and shear rate around 10² s⁻¹ at 5 L/min. Acquisition on two orthogonal planes provided a qualitative view of the three-dimensional flow, revealing the rotation and spatial migration of the main vortex. Finally, comparison between the Epygon–Perimount and Epygon–tilting disk configurations revealed negligible differences in velocity and vorticity, suggesting that the type of aortic valve does not significantly affect mitral inflow and ventricular fluid dynamics. In conclusion, the results indicate that the Epygon mitral valve, thanks to its asymmetric geometry and single leaflet, effectively reproduces physiological intraventricular flow across the analyzed range of CO.