Development of an <em>Ex Vivo</em> Mitral Valve Evaluation Model Using a Pulsatile Flow Simulator

Surgical mitral valve repair remains a challenging procedure. Although several repair techniques have been defined, data comparing their hemodynamic effects are lacking. The commercially available pulse duplicators are commonly used to simulate blood circulation through mechanical or 3D printed cardiac valves. However, due to the specific structure and working mechanism of the mitral valve, the experiments on surgical techniques require the use of biological tissues. Ex vivo lamb mitral valves are suitable for such experiments, but the methods for mounting these valves to the pulse duplicator system (PDS) are not well defined. To address this, we modified the system by 3D printing and silicone molding as a mitral valve holder. We excised the mitral valve from a lamb heart for each experiment, including its annulus and subvalvar apparatus. We implanted this into the atrioventricular (mitral) valve area of the test machine using the silicone holder. Papillary muscle tension was simulated by tying sutures around the chordae-papillary junctions and passing these sutures through the release hole at the bottom of the ventricular chamber. Initial testing of the valve competence was conducted at a heart rate of 120 beats per minute and a cardiac output of 2 L/min. Valve regurgitation and the pressure gradient between the atrial and ventricular chambers were measured using pulse duplicator electromagnetic flowmeters and validated with echocardiography. Baseline hemodynamic testing demonstrated consistent valve function across five experiments, with a mean regurgitation fraction of 21.1% and echo-derived transmitral gradients ranging from 5.15 to 8.13 mmHg. Stroke volumes and peak flow rates varied among specimens, reflecting physiological variability within the pediatric model.