The need to account for residual strains and composite nature of heart wall in mechanical analyses

Kang, Taehak; Yin, F. C. P.

doi:10.1152/ajpheart.1996.271.3.h947

Cited by 10 publications

(8 citation statements)

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“…The VP tensile strength is more than an order of magnitude greater than that of any other portion of the myocardium, which agrees with the greater hydroxyproline content found in this layer (26). In addition, the epicardium with the VP has greater stiffness than the intact endocardium (16,26).…”

Section: Discussionsupporting

confidence: 71%

The visceral pericardium: macromolecular structure and contribution to passive mechanical properties of the left ventricle

Jobsis

Ashikaga²,

Wen

et al. 2007

American Journal of Physiology-Heart and Circulatory Physiology

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Much attention has been focused on the passive mechanical properties of the myocardium, which determines left ventricular (LV) diastolic mechanics, but the significance of the visceral pericardium (VP) has not been extensively studied. A unique en face three-dimensional volumetric view of the porcine VP was obtained using two-photon excitation fluorescence to detect elastin and backscattered second harmonic generation to detect collagen, in addition to standard light microscopy with histological staining. Below a layer of mesothelial cells, collagen and elastin fibers, extending several millimeters, form several distinct layers. The configuration of the collagen and elastin layers as well as the location of the VP at the epicardium providing a geometric advantage led to the hypothesis that VP mechanical properties play a role in the residual stress and passive stiffness of the heart. The removal of the VP by blunt dissection from porcine LV slices changed the opening angle from 53.3 +/- 10.3 to 27.3 +/- 5.7 degrees (means +/- SD, P < 0.05, n = 4). In four porcine hearts where the VP was surgically disrupted, a significant decrease in opening angle was found (35.5 +/- 4.0 degrees ) as well as a rightward shift in the ex vivo pressure-volume relationship before and after disruption and a decrease in LV passive stiffness at lower LV volumes (P < 0.05). These data demonstrate the significant and previously unreported role that the VP plays in the residual stress and passive stiffness of the heart. Alterations in this layer may occur in various disease states that effect diastolic function.

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Section: Discussionsupporting

confidence: 71%

The visceral pericardium: macromolecular structure and contribution to passive mechanical properties of the left ventricle

Jobsis

Ashikaga²,

Wen

et al. 2007

American Journal of Physiology-Heart and Circulatory Physiology

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“…The collagenous epicardium and parietal pericardium are distinctly different in material properties from myocardium, being more compliant and isotropic at low biaxial strains and much stiffer and more anisotropic at higher strains (Humphrey et al 1990c). Biaxial tests also indicated that the epicardium may significantly influence the mechanics of the underlying subepicardial muscle (Kang & Yin 1996). ; b Omens et al (1993).…”

Section: (A) Biaxial Testing Of Excised Myocardiummentioning

confidence: 99%

Modelling cardiac mechanical properties in three dimensions

Costa¹,

Holmes²,

McCulloch

2001

Philosophical Transactions of the Royal Society of London. Seri

247

232

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The central problem in modelling the multi-dimensional mechanics of the heart is in identifying functional forms and parameters of the constitutive equations, which describe the material properties of the resting and active, normal and diseased myocardium. The constitutive properties of myocardium are three dimensional, anisotropic, nonlinear and time dependent. Formulating useful constitutive laws requires a combination of multi-axial tissue testing in vitro, microstructural modelling based on quantitative morphology, statistical parameter estimation, and validation with measurements from intact hearts. Recent models capture some important properties of healthy and diseased myocardium including: the nonlinear interactions between the responses to different loading patterns; the influence of the laminar myofibre sheet architecture; the effects of transverse stresses developed by the myocytes; and the relationship between collagen fibre architecture and mechanical properties in healing scar tissue after myocardial infarction.

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“…The presence of significant residual stress is most notably demonstrated by the tendency of rings of the arterial wall to open when cut radially (8,49). From a biomechanical standpoint, residual stresses (and the associated residual strains) play a key role in the identification of an appropriate "zero-stress" reference configuration and hence impact the definition of mechanical stresses and strains in the tissue (8,23,34). From a physiological standpoint, knowledge of the mechanisms underlying acute and chronic changes in residual stress are also required for understanding how growth and remodeling influence the mechanical homeostasis in vascular tissue (22,30,32,46,47).…”

mentioning

confidence: 99%

Heterogeneous transmural proteoglycan distribution provides a mechanism for regulating residual stresses in the aorta

Azeloglu¹,

Albro²,

Thimmappa³

et al. 2008

American Journal of Physiology-Heart and Circulatory Physiology

128

150

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The arterial wall contains a significant amount of charged proteoglycans, which are inhomogeneously distributed, with the greatest concentrations in the intimal and medial layers. The hypothesis of this study is that the transmural distribution of proteoglycans plays a significant role in regulating residual stresses in the arterial wall. This hypothesis was first tested theoretically, using the framework of mixture theory for charged hydrated tissues, and then verified experimentally by measuring the opening angle of rat aorta in NaCl solutions of various ionic strengths. A three-dimensional finite element model of aortic ring, using realistic values of the solid matrix shear modulus and proteoglycan fixed-charge density, yielded opening angles and changes with osmolarity comparable to values reported in the literature. Experimentally, the mean opening angle in isotonic saline (300 mosM) was 15 +/- 17 degrees and changed to 4 +/- 19 degrees and 73 +/- 18 degrees under hypertonic (2,000 mosM) and hypotonic (0 mosM) conditions, respectively (n = 16). In addition, the opening angle in isotonic (300 mosM) sucrose, an uncharged molecule, was 60 +/- 16 degrees (n = 11), suggesting that the charge effect, not cellular swelling, was the major underlying mechanism for these observations. The extent of changes in opening angle under osmotic challenges suggests that transmural heterogeneity of fixed-charge density plays a crucial role in governing the zero-stress configuration of the aorta. A significant implication of this finding is that arterial wall remodeling in response to altered wall stresses may occur via altered deposition of proteoglycans across the wall thickness, providing a novel mechanism for regulating mechanical homeostasis in vascular tissue.

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The need to account for residual strains and composite nature of heart wall in mechanical analyses

Cited by 10 publications

References 0 publications

The visceral pericardium: macromolecular structure and contribution to passive mechanical properties of the left ventricle

The visceral pericardium: macromolecular structure and contribution to passive mechanical properties of the left ventricle

Modelling cardiac mechanical properties in three dimensions

Heterogeneous transmural proteoglycan distribution provides a mechanism for regulating residual stresses in the aorta

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