Sarcomere length changes in a 3D mathematical model of the pig ventricles

Abstract

Measurements of the geometry and fibrous-sheet structure of the left and right ventricles of the pig heart are fitted with a finite element model. Mechanical changes during the heart cycle are computed by solving the equations of motion under specified ventricular boundary conditions and using experimentally defined constitutive laws for the active and passive material properties of myocardial tissue. The resulting patterns of deformation, such as axial torsion and changes in wall thickness and base-apex length, are consistent with experimental observations. The model can therefore be used to predict sarcomere length changes and other strain patterns throughout the myocardium and throughout the cardiac cycle. Here we present sarcomere length changes at a limited number of material points within the wall. Sarcomere length typically varies by 10% above and below the unloaded length; although under the boundary conditions imposed in the current model the midwall circumferentially oriented sarcomere lengths increased by up to 20% at end diastole. We provide web-access details for a downloadable software program designed to provide more extensive information on mechanical deformation, such as the principal strains and muscle fibre cross-sectional area changes during the cardiac cycle.

The Frank–Starling mechanism in vertebrate cardiac myocytes

“…Fig.·1A). Work has been carried out on mammalian hearts which characterize the changes in SL that actually occur during the in vivo cardiac cycle (Stevens and Hunter, 2003). This entailed detailed structural mapping because strain is influenced by fibre orientation (Gilbert et al, 2007).…”

Stretch of Contracting Cardiac Muscle Abruptly Decreases the Rate of Phosphate Release at High and Low Calcium

“…Experiments were done at both high (maximally activating) and lower, half-maximally activating [Ca 2ϩ ], which is more relevant to in vivo function. During systole the volume of the ventricle decreases as working cardiomyocytes shorten, but there is regional variation within the ventricle wall, with some cardiomyocytes being stretched at the beginning of systole by the incoming blood or neighboring myocyte contraction (1)(2)(3). We have measured the effects of stretch on force and P i release rate by applying ramp stretches to isometrically contracting trabeculae obtained from rat hearts.…”

Functionally and Structurally Integrated Computational Modeling of Ventricular Physiology

“…Models have been developed of the geometry and myofiber architecture of the dog ventricles [38], rabbit ventricles [39], pig ventricles [40] and human atria [41,42]. Although most detailed anatomic models have been developed from painstaking dissections and histological reconstructions, diffusion tensor magnetic resonance imaging has emerged as an alternative method for imaging myofiber architecture in fixed tissues [43,44] Because of interest in genetically engineered mouse models for studies of the molecular pathogenesis of inherited and acquired heart disease, there is an increasing need for a model of the mouse ventricles.…”

“…The development of anatomically detailed models of cardiac geometry and muscle fiber architecture has enabled investigators to develop structurally integrated continuum models of cardiac electrical impulse propagation [28,45] and wall mechanics [40] using finite volume, finite dif-ference, or finite element methods. As cellular models become more biophysically detailed and functionally integrated, the opportunity arises for structurally integrated models that are also functionally integrated, such as continuum models of coupled ventricular electromechanics [46][47][48][49][50].…”