Development of an Ex Vivo Mitral Valve Evaluation Model Using a Pulsatile Flow Simulator

Summary

We present an ex vivo model for mounting lamb mitral valves into a pulsatile simulator to assess valve function under physiologic conditions. This setup enables quantitative evaluation of mitral valve dynamics using biological tissue in a reproducible, anatomically accurate configuration.

Abstract

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.

Introduction

Mitral valve repair has evolved significantly, with contemporary surgical techniques offering enhanced efficacy and improved long-term outcomes¹. Although many centers have standardized mitral repair strategies, a persistent gap remains in the comprehensive evaluation of the hemodynamic impact of these interventions². Optimizing repair strategies, particularly for anatomically complex or pediatric cases, requires models that allow for controlled, repeatable physiological testing.

The primary objective of this study was to develop a reproducible ex vivo model using biological mitral va....

Protocol

This study was conducted using lamb hearts obtained post-mortem from a licensed abattoir. According to the decision of the Istanbul University-Cerrahpaşa Local Ethics Committee for Animal Experiments (2025/11), this work falls under the exemption outlined in Article 8 (8-k1) of the HADYEK directive and therefore did not require ethical approval .

1. Experiment setup

1. Duplicate the mitral inflow component of the pulse duplicator system using 3D modeling software. Create a digital copy of the existing geometry to ensure compatibility. Print the design using PLA filament on a 3D printer. Use the printed mold to....

Results

Baseline hemodynamic data were obtained from five ex vivo experiments using native mitral valves mounted in a custom silicone holder within a pulse duplicator system. The model was perfused under standardized pediatric physiological conditions (cardiac output: 2 L/min; HR: 120 bpm), and functional assessments were performed using pressure transducers and echocardiographic imaging.

The regurgitation fraction ranged from 15.9% to 26.6%, with a mean of 21.1% ± 5.3%. Stroke volume varied .......

Discussion

The objective of this study was to develop a model replicating the mitral valve under pediatric hemodynamic state, which guided our choice to use lamb hearts as the experimental basis. This selection was driven by the close resemblance in dimensions between the lamb mitral valve and that of pediatric patients. Anatomically, the lamb heart exhibits a more ventrally tilted orientation along its longitudinal axis compared to the human heart and possesses a relatively blunt apex composed entirely of the left ventricle

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
2-0 Coated Braided Polyester Suture	Covidien	88863230-56	Stabilization of papillary muscles during testing
3D Printer	Ultimaker	Ultimaker S3	Used for fabricating custom silicone molds
5-0 Monofilament Polypropylene Suture, Double Armed	Covidien	VPF-720-X	Suturing the valve to the silicone mold
DeBakey Atraumatic Forceps	Aesculap	MB062R	Tissue handling during dissection
Fresh Lamb Hearts	Licensed Abattoir	—	Source of native mitral valves
Mayo Dissection Scissors	Aesculap	BC252B	General cardiac dissection
Micro Needle Holder	Aesculap	FM538R	Suturing the mitral valve
Nelson-Metzenbaum Scissors	Aesculap	BC606R	Used for suture cutting
Pulse Duplicator System	ViVitro Labs	18363	Simulated physiologic flow for valve testing
Silicone Molds	—	Custom-fabricated	Used to replicate ventricular geometry
Sterile Saline (0.9%)	Elabscience	PB180353	Medium for perfusion circuit