Comparison of biaxial mechanical properties of excised endocardium and epicardium

Abstract

A complete understanding of cardiac mechanics requires knowledge of the mechanical properties of each of the tissues that comprise the heart, Data and constitutive relations are available for the nonlinear multiaxial behavior of epicardium and noncontracting myocardium, but there have been no comparable results for endocardium. In this paper, we present biaxial mechanical data for endocardium and epicardium excised from the same bovine hearts. The data reveal that these two membranes behave differently; endocardium exhibits a greater stiffness in the low-strain range. Moreover, quantification of endocardial behavior requires a seven-parameter, polynomial-exponential pseudostrain-energy function w, whereas epicardium can be described by a four-parameter exponential w. Comparison of our current findings with previous results on canine epicardium reveals further that canine and bovine epicardium behave similarly, although the latter is more extensible. Thus there appear to be marked species differences.

A passive strain-energy function for elastic and muscular arteries: correlation of material parameters with histological data

“…The appearance of an exponential term was unanimous with past studies, whereas the quadratic term was dictated by our low-stress mechanical results and behavior of other elastin-rich tissues, including arteries [1,5,31,44], visceral pleura [20], and cardiac tissue, i.e., parietal pericardium [2] and endocardium [22]. All experimental data were fitted well with the chosen SEF.…”

Biomechanical and histological characteristics of passive esophagus: Experimental investigation and comparative constitutive modeling

“…The incapacity of biphasic models to offer improved reproduction of the experimental responses of esophageal tissue may be ascribed to that these were developed to capture the sigmoidal biomechanical response of elastic arteries (Demiray et al, 1986;Fung et al, 1993;Weizsäcker et al, 1995;Holzapfel and Weizsäcker, 1998) and other elastin-rich tissues, such as skin (Tong and Fung, 1976) and endocardium (Kang et al, 1996). The sigma-shaped response of those tissues necessitates the use of two-part SEFs, since a single exponential function may be unable to capture the multiple convexities present.…”

“…We finally examined the quadratic and exponential SEF proposed by Tong and Fung (1976) to model the biphasic response of skin, and later applied by Demiray et al (1986) and Fung et al (1993) for arteries, Humphrey et al (1987) for visceral pleura, Chew et al (1986) for pericardium, and Kang et al (1996) for endocardium:…”

Complex distributions of residual stress and strain in the mouse left ventricle: experimental and theoretical models

“…To find out what the actual residual stress field is like in myocardium, we need to know an appropriate constitutive law for myocardium and how that law changes from the endocardium to the epicardium. Additionally, the endocardium and epicardium are residually stressed and have constitutive behavior that differs from that of myocardium (Kang et al 1996). These membranes should be included in future deterministic models.…”