In this study, we present a left heart simulator that allows for the installation and comparison of different MV models, the assessment of their dynamics, and the simulation of interventions to treat MV pathologies. In contrast to existing simulators, it combines the following features: the generation of a realistic hemodynamic environment, the incorporation of the entire MV apparatus, the ability to perform surgical and cardiac interventions, and detailed measurement capabilities by sensors.

It is crucial to replicate the in-vivo hemodynamic settings to enable a realistic training of physicians. This realistic hemodynamic environment was generated by simulators developed by Bazan et al. [18] and Paulsen et al. [19]. However, these simulators do not allow for the performance of MV repair. In contrast, simulators for MV repair introduced by Sardari et al. [20] and Gollmann-Tepeköylü et al. [11] either lack a hemodynamic environment or quantitative measurements of pressure or flow. The simulator presented here combines both, a realistic hemodynamic environment, as well as the opportunity to train MIMVS and TEER.

To create a realistic hemodynamic environment for competent MVs, we used both biological and mechanical prosthetic MVs. Additionally, the use of ex-vivo porcine valves enabled evaluation of the simulator’s functionality with human-like MVs. Both the prosthetic and porcine MVs induced physiological pressures and flows. The pathological and repaired valves accurately reproduced known in-vivo conditions with MR grades ranging from 0 to 3.

The integration of the entire MV apparatus is essential for modelling MR pathologies and their treatment. While previously reported simulators for training and planning do not allow for the implementation of papillary muscles [12, 21], simulators solely used for research, such as the ones introduced by Paulsen et al. [19] and Rabbah et al. [22], and our simulator enable the integration of the entire MV apparatus, including the annulus, leaflets, chordae tendineae, and papillary muscles. This allowed us to model pathologies such as chordae tendineae rupture and annulus dilatation, which resulted in impaired valve competency and moderate MR (grade 2).

While simulations on whole porcine hearts, as reported by Gollmann-Tepeköylü et al. [11], allow for training of TEER only on certain pathologies or even on healthy MVs, our simulator also enables the integration of patient-specific silicone valves. Most importantly, this is a step towards facilitating pre-operative patient-specific planning in a hemodynamic environment, which is not possible with currently available simulators.

MIMVS and TEER are major therapies for treating MR, performed in cardiac surgery and cardiology, respectively. While MIMVS is performed on the arrested heart via transthoracic access, TEER is performed on the beating heart via transseptal access. Existing devices for simulating therapeutic procedures provide either transthoracic access (Sadari et al. [20]) or transseptal access (Gollmann-Tepeköylü [11]) in a realistic setup, or no realistic access at all (Boone et al. [21], Ginty et al. [12], Paulsen et al. [19]), as the MV apparatus must be completely removed from the simulator to perform procedures. In contrast, the simulator presented here realistically mimics both types of access, allowing for the simulation of both interventions in one device.

In the future, the simulator may potentially be used to practice and model additional techniques. Transseptal interventions such as the Cardioband and ChordArt could likely be integrated without design changes, whereas approaches like the Harpoon system or MitralStitch would require design modifications. However, their integration is facilitated by the modular construction of the simulator.

The feasibility to evaluate the hemodynamic condition quantitatively and qualitatively with the MV is a fundamental requirement for comparing different techniques or monitoring the training progress of a physician. Existing simulators including a hemodynamic setting either offer no flow and pressure data [11] or pressure measurements without flow data [12, 21]. In contrast, our simulator is compatible with transesophageal echocardiography (TEE) during experiments with porcine and patient-specific MVs. Moreover, additional tools are implemented to measure and monitor pressure and flow in real-time, allowing for a more detailed observation of the simulation.

Although our simulator reproduces a realistic environment for MV, and therapies to treat MR, a few aspects may be improved in the future. The tensioning system for the subvalvular apparatus should allow more adjustments due to the potential three-dimensional repositioning of papillary muscles forced by interventional influences. Furthermore, TEER training under fluoroscopy would improve the monitoring of the TEER-system once it passes the MV orifice, but would expose the physicians to radiation and would require more infrastructure for the simulation. Additionally, the rigid material of the simulator with its higher echogenicity limits the orientation and navigation in the echocardiographic image. For example, the aorta is hardly visible, but traditionally used as a reference marker by the echocardiographer.