Quantification of Material Constants for a Phenomenological Constitutive Model of Porcine Tricuspid Valve Leaflets for Simulation Applications

Abstract

The tricuspid valve is a one-way valve on the pulmonary side of the heart, which prevents backflow of blood during ventricular contractions. Development of computational models of the tricuspid valve is important both in understanding the normal valvular function and in the development/improvement of surgical procedures and medical devices. A key step in the development of such models is quantification of the mechanical properties of the tricuspid valve leaflets. In this study, after examining previously measured five-loading-protocol biaxial stress-strain response of porcine tricuspid valves, a phenomenological constitutive framework was chosen to represent this response. The material constants were quantified for all three leaflets, which were shown to be highly anisotropic with average anisotropy indices of less than 0.5 (an anisotropy index value of 1 indicates a perfectly isotropic response, whereas a smaller value of the anisotropy index indicates an anisotropic response). To obtain mean values of material constants, stress-strain responses of the leaflet samples were averaged and then fitted to the constitutive model (average R2 over 0.9). Since the sample thicknesses were not hugely different, averaging the data using the same tension levels and stress levels produced similar average material constants for each leaflet.

Dilation of tricuspid valve annulus immediately after rupture of chordae tendineae in ex-vivo porcine hearts

“…An increase in the annulus area following chordae rupture may change the annulus tension and alter the homeostatic mechanical environment to which the leaflets and the myocardium surrounding the annulus are subjected. The homeostatic mechanical environment is extremely important for the normal function of the TV and its surrounding tissues and can alter its normal mechanical properties [ 5 , 24 ]. In all types of cardiac valves, valve interstitial cells reside within the leaflet tissue [ 36 – 40 ].…”

“…The leaflets and annulus of the TV undergo complicated dynamic deformations during normal cardiac cycles [ 1 , 2 ]. Any disturbance in the normal deformation of the valve leaflets and/or annulus could lead to valvular regurgitation [ 3 , 4 ] and changes in the valve’s mechanical response [ 5 , 6 ]. In most cases, TV regurgitation—whether it is caused by primary valvular lesions (e.g., due to congenital malformations [ 7 ], trauma [ 8 , 9 ] or degenerative diseases such as Marfan syndrome [ 10 , 11 ]) or takes place as a result of other cardiovascular diseases (e.g.…”

“…Previous studies have shown that acute biomechanical changes in cardiac valves could induce remodeling responses that may negatively affect the valve structure, mechanical properties, and function [ 5 , 22 , 23 ]. Considering the importance of such acute events, in this study we aimed to identify how TV regurgitation develops immediately following chordae rupture.…”

Soft-Tissue Material Properties and Mechanogenetics during Cardiovascular Development

“…Embryonic data on biomechanical properties of bovine and ovine cardiovascular components are limited. Despite the ample biomechanical data on mature porcine heart valves [28,[79][80][81][82], limited embryonic studies have been conducted to our knowledge. Ovine arterial pressure at the fetal stage was measured for different gestational ages.…”

Mechanics of the Tricuspid Valve—From Clinical Diagnosis/Treatment, In-Vivo and In-Vitro Investigations, to Patient-Specific Biomechanical Modeling

“…Pressure systems, on the other hand, operate by applying a pressure to the ventricles to force full leaflet closure, allowing analyses of the pressurized valve statically. There is an exception to pressure or flow systems for in-vitro analysis of heart operation to create active beating hearts, known as the Langendorff or the working heart model (Figure 7c) [107]. In these models, the human/ovine/porcine heart is retrieved immediately preceding the human or animal death and the organ is placed into a flow system and perfused with a solution to provide cell nutrients and maintain cell life.…”