# Development of Heart Simulator and Analysis of Valve Dysfunction in Tricuspid Regularization
## 1 Introduction  
Recently, tricuspid regurgitation (TR) has become increasingly prevalent among patients over the age of 75, significantly impacting their quality of life [1]. Particularly, TR during this period often progresses to a severe stage with a very poor prognosis. With human life expectancy now extending beyond 80 years, this represents a significant issue. Surgical approaches to addressing this, compared to mitral or aortic surgery, are associated with higher postoperative mortality rates, necessitating a non-surgical approach [2, 3]. Therefore, this study aims to suppress TR through non-surgical means and approach the phenomenon of TR from a signal analysis perspective.  
From a biomechanics standpoint, the tricuspid valve (TV) displays anisotropic elasticity. Its elasticity is lower in the forward flow direction but higher in the reverse. As the heart undergoes age-related structural changes, there is a drop in its forward elasticity and a rise in the reverse elasticity. This shift hinders the heart from effectively preventing retrograde flow, resulting in a dysfunctional valve. Moreover, arteriosclerosis shows that blood vessel fluid resistance escalation obstructs blood egress from the heart. Consequently, there is blood buildup, enlarging the heart's volume. These compounded issues strain the valve, causing heart and valve malfunctions, such as TR [4; 5].  
TR arises due to structural abnormalities of the TV. The causes can include valve leaflet prolapses, TV annular dilation, or ruptures in the chordae tendineae. The extent of TR's severity is gauged based on the regurgitation magnitude and its effects on a patient's hemodynamics. Diagnosis and assessment tools include echocardiography, cardiac catheterization, and Doppler ultrasound [6; 7; 8].  
Prior to this study, we had developed a membrane-based structure to manage TR and successfully tested its effectiveness in controlling TR in in vivo porcine hearts [9]. We named this structure the Pivot-TR device (TAU MEDICAL Inc., Yangsan, Republic of Korea). A simulator was needed to mimic the heart's structure mechanically for a quantitative performance evaluation of this device and its aging tests. This paper encompasses the development of this simulator and methods to evaluate the performance of the tricuspid-valve assistive structure device (Pivot-TR) by atrial-pressure-time data and STFT, along with its limitations and potential improvements.  
During the development of Pivot-TR, it became evident that indirect imaging methods, like magnetic resonance imaging (MRI) and ultrasound, have limitations in capturing the biomechanical behavior of the Pivot-TR. This realization necessitated optical imaging methods like endoscopy [10]. Thus, this study needed to begin and create a test bench suitable for experiments in ex vivo conditions. This test bench should be able to provide an environment in which atrial pressure and heart rate can be tested as control variables [11].  
In this research, we aim to develop a flow simulator that represents the basic appearance of hemodynamics in the heart affected by TR. Using the simulator and ex vivo porcine hearts, we aim to observe changes in blood pressure and flow. The research verifies the reproducibility of these observations and, when inserting a structure to alleviate TR and assist the valve function, determines how much the valve function is restored and how blood flow and pressure are adjusted.