Impact of Material Anisotropy on Deformation of Myocardial Tissue due to Pacemaker Electrodes

2011 ◽  
Author(s):  
Caroline Forsell ◽  
T. Christian Gasser
Keyword(s):  
Numerical Simulations ◽  
Myocardial Tissue ◽  
Rigid Punch ◽  
Anisotropic Model ◽  
Material Anisotropy ◽  
Ventricular Tissue ◽  
Hyperelastic Model ◽  
Pacemaker Electrodes ◽  
Heart Wall

A Pacemaker electrode can penetrate the heart wall, and to design a penetration-resistent lead tip sound knowledge regarding failure of ventricular tissue is required. Numerical simulations can be particular helpful in that respect, but depend on a reliable constitutive description for ventricular tissue. In this study an anisotropic hyperelastic model for the myocardium has been implemented and compared to predictions from an isotropic description. Specifically, the response due to pushing a rigid punch into the myocardium was studied. Results between anisotropic and isotropic descriptions of the myocardium differed significantly, which justified the implementation of an anisotropic model for the myocardium.

scholarly journals Understanding regional mechanics of rat myocardia by fitting hyperelatsic models

2021 ◽  
Author(s):  
Fulufhelo Nemavhola ◽  
Harry Ngwangwa ◽  
Thanyani Pandelani ◽  
Neil Davies ◽  
Thomas Franz
Keyword(s):  
Rat Heart ◽  
Goodness Of Fit ◽  
Regional Difference ◽  
Computational Models ◽  
Coefficient Of Determination ◽  
Myocardial Tissue ◽  
Biaxial Test ◽  
Anisotropic Model ◽  
Septal Wall ◽  
Hyperelastic Model

Abstract Availability of biaxial mechanical data for heart myocardia remains high in demand for the development of accurate and detailed computational models. The aim of this study is to study the regional difference of wall mechanics using rat heart in the left ventricle (LV), septal wall (STW) and right ventricle (RV). This was achieved by conducting a biaxial test on three rat heart myocardia (i.e LV, RV and STW). Fung, Choi-Vito, Polynomial (Anistropic), Four-Fiber family, Holzapfel (2000) and Holzapfel (2005) hyperelastic models were selected and fitted on the bixial data of the LV, RV and STW. The best hyperelastic model was the selected based on evaluation index (EI) determined from the coefficient of determination (R2). All the six models were then compared in all three rat heart myocardia. The results show that the Polynomial (Anisotropic) model outperforms the other five models in all myocardial tissues with EI’s above 90 % goodness of fit. The Four-fiber-family and the two Holzapfel models perform equally in the LV and STW myocardial tissue between 50 and 70 % goodness of fit. The Fung and Choi-Vito models yielded poor goodness of fit in the LV and STW myocardial tissues. Parameter fitting is useful method in advancing reliable data to be used in the development of accurate computational models.

Abstract 17097: Non-Synonymous Mitochondrial DNA Variants Are Common in Myocardial Tissue of Heart Failure Patients

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Pappu Ananya ◽  
Michael Binder ◽  
Yang Wanjun ◽  
Rebecca McClellan ◽  
Brittney Murray ◽  
...  
Keyword(s):  
Heart Failure ◽  
Mitochondrial Dna ◽  
Nuclear Dna ◽  
Left Ventricular ◽  
Individual Risk ◽  
Myocardial Tissue ◽  
Mtdna Mutation ◽  
Mtdna Mutations ◽  
Ventricular Tissue ◽  
Mtdna Variants

Introduction: Mitochondrial heart disease due to pathogenic mitochondrial DNA (mtDNA) mutations can present as hypertrophic or dilated cardiomyopathy, ventricular arrhythmias and conduction disease. It is estimated that the mutation rate of mtDNA is 10 to 20-fold higher than that of nuclear DNA genes due to damage from reactive oxygen species released as byproducts during oxidative phosphorylation. When a new mtDNA mutation arises, it creates an intracellular heteroplasmic mixture of mutant and normal mtDNAs, called heteroplasmy. Heteroplasmy levels can vary in various tissues and examining mtDNA variants in blood may not be representative for the heart. The frequency of pathogenic mtDNA variants in myocardial tissues in unknown. Hypothesis: Human ventricular tissue may contain mtDNA mutations which can lead to alterations in mitochondrial function and increase individual risk for heart failure. Methods: Mitochondrial DNA was isolated from 61 left ventricular myocardial samples obtained from failing human hearts at the time of transplantation. mtDNA was sequenced with 23 primer pairs. In silico prediction of non-conservative missense variants was performed via PolyPhen-2. Heteroplasmy levels of variants predicted to be pathogenic were quantified using allele-specific ARMS-PCR. Results: We identified 21 mtDNA non-synonymous variants predicted to be pathogenic in 17 hearts. Notably, one heart contained four pathogenic mtDNA variants (ATP6: p.M104; ND5: p.P265S; ND4: p.N390S and p.L445F). Heteroplasmy levels exceeded 90% for all four variants in myocardial tissue and were significantly lower in blood. No pathogenic mtDNA variants were identified in 44 hearts. Hearts with mtDNA mutations had higher levels of myocardial GDF-15 (growth differentiation factor-15; 6.2±2.3 vs. 1.3±0.18, p=0.045), an established serum biomarker in various mitochondrial diseases. Conclusions: Non-synonymous mtDNA variants predicted to be pathogenic are common in human left ventricular tissue and may be an important modifier of the heart failure phenotype. Future studies are necessary to correlate myocardial mtDNA mutations with cardiovascular outcomes and to assess whether serum GDF-15 allows identifying patients with myocardial mtDNA mutations.

The mechanisms of action of noradrenaline on ouabain-sensitive rubidium uptake in guinea-pig myocardium

1985 ◽  
Vol 69 (6) ◽  
pp. 737-743 ◽  
Author(s):  
Richard B. Wanless ◽  
Mark I. M. Noble ◽  
Angela J. D. Drake-Holland
Keyword(s):  
Guinea Pig ◽  
Adrenergic Receptor ◽  
Extracellular Potassium ◽  
Myocardial Tissue ◽  
Stimulatory Action ◽  
Extracellular Potassium Concentration ◽  
Rubidium Uptake ◽  
Low Concentrations ◽  
Ventricular Tissue ◽  
High Doses

1. The mechanism by which noradrenaline stimulates ouabain-sensitive rubidium uptake in guinea-pig myocardial tissue has been studied. 2. The stimulatory action of low concentrations of noradrenaline was reversed by high doses of propranolol (10−5 mol/l) in atrial tissue, but was not reversed by α- or β-, or combined α- and β-adrenoceptor antagonists in ventricular tissue. 3. Rubidium uptake was also found to increase with increasing extracellular potassium concentration ([K]o). The percentage values of stimulation by noradrenaline decreased with increasing [K]o. 4. Noradrenaline had no effect on the rate of ATP splitting by an isolated membrane preparation of Na,K-ATPase. 5. It is proposed that noradrenaline stimulates active cation transport by either (a) an effect secondary to increased passive efflux of K ions, or (b) an action at a novel adrenergic receptor, distinct from the ATPase enzyme itself.

Experimental and Numerical Investigations for Quantifying Variability of NR Mechanical Properties after Thermal Aging

2020 ◽  
pp. 000-000
Author(s):  
Andrés Malo Estepa ◽  
Franck Massa ◽  
Adnane Boukamel ◽  
Thierry Tison ◽  
Philippe Champagne ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Black ◽  
Numerical Simulations ◽  
Thermal Aging ◽  
Kriging Model ◽  
Dynamic Simulations ◽  
Numerical Investigations ◽  
Different Temperatures ◽  
Hyperelastic Model

ABSTRACT The evolution of mechanical properties of NR with carbon black fillers was examined after a thermal aging step through both experimentation and non-deterministic numerical simulations. A quantification of mechanical properties and associated variability is first proposed for a set of specimens exposed at different temperatures and exposure times. Second, a family of stretch–stress laws is numerically built with a James' hyperelastic model. Next, the whole of the behavior evolution is modeled with a Kriging model to quantify the effects of properties on a macroscopic stiffness, useful in dynamic simulations, and the least-favorable scenario is so determined. Finally, Arrhenius method is performed to numerically draw the evolution bounds of macroscopic stiffness as a function of aging exposure, followed by a comparison with a naturally aged suspension component. To our knowledge, the methodology developed has not already been proposed in this area.

scholarly journals Biomechanical behaviour and hyperelastic model parameters identification of sheep omasum

2021 ◽  
Author(s):  
Lebohang Lebea ◽  
Harry Ngwangwa ◽  
Thanyani Pandelani ◽  
Fulufhelo Nemavhola
Keyword(s):  
Fatty Acids ◽  
Volatile Fatty Acids ◽  
Biomechanical Properties ◽  
Parameters Identification ◽  
Coefficient Of Determination ◽  
Model Parameters ◽  
Anisotropic Model ◽  
Average Coefficient ◽  
Hyperelastic Model ◽  
Hyperelastic Models

Abstract The function of the omasum is incompletely understood; however, the omasum plays an important role in the transport of appropriately sized feed particles from the reticulorumen to the abomasum, oesophageal groove closure, fermentation of ingesta, and absorption of water, volatile fatty acids, and minerals. The aim of this study is to evaluate the suitable hyperelastic anisotropic model based on biomechanical properties of sheep omasum. The results show that all five (5) hyperelastic models may be suitable for the evaluation of sheep omasum. The average coefficient of determination (R2) of Fung, Polynomial (Anisotropic), Holzapfel (2000), Holzapfel (2005) and Four-Fiber-Family hyperelastic models were found to be 0.79 ± 0.19, 0.95 ± 0.05, 0.92 ± 0.07, 0.93 ± 0.05 and 0.94 ± 0.03, respectively. Also, it was found that the best hyperelastic model for fitting uniaxial data of the sheep omasum was Polynomial (Anisotropic) with EI of 100.0 followed by the Four-Fiber-Family model with EI of 96.18.

scholarly journals FITTING OF HYPERELASTIC CONSTITUTIVE MODELS IN DIFFERENT SHEEP HEART REGIONS BASED ON BIAXIAL MECHANICAL PROPERTIES

2021 ◽  
Author(s):  
Fulufhelo Nemavhola ◽  
Thanyani Pandelani ◽  
Harry Ngwangwa
Keyword(s):  
Heart Failure ◽  
Causes Of Death ◽  
Mechanical Response ◽  
Constitutive Models ◽  
Myocardial Tissue ◽  
Anisotropic Model ◽  
Tissue Responses ◽  
Biaxial Mechanical Properties ◽  
Best Fit ◽  
Fung Model

Heart failure remains one of the leading causes of death especially among people over the age of 60 years worldwide. To develop effective therapy and suitable replacement materials for the heart muscle it is necessary to understand its biomechanical behaviour under load. This paper investigates the passive mechanical response of the sheep myocardia excised from three different regions of the heart. Due to the relatively higher cost and huge ethical demands in acquisition and testing of real animal heart models, this paper evaluates the fitting performances of five different constitutive models on the myocardial tissue responses. Ten sheep were sacrificed, and their hearts excised and transported within 3h to the testing biomechanical laboratory. The upper sections of the hearts above the short axes were carefully dissected out. Tissues were dissected from the mid-sections of the left ventricle, mid-wall and right ventricle for each heart. The epicardia and endocardia were then carefully sliced off each tissue to leave the myocardia. Stress-strain curves were calculated, filtered and resampled. The results show that Choi-Vito model was found to provide the best fit to the LV, the polynomial (Anisotropic) model to RV, the Four-Fiber Family model to RV, Holzapfel (2000) to RV, Holzapfel (2005) to RV and the Fung model to LV.

The innervation of toad lymph hearts: An ultrastructural study

1992 ◽  
Vol 50 (1) ◽  
pp. 898-899
Author(s):  
A.M. Pucci ◽  
C. Fruschelli ◽  
A. Rebuffat ◽  
M. Guarna ◽  
C. Alessandrini ◽  
...  
Keyword(s):  
Ultrastructural Study ◽  
Neuromuscular Junctions ◽  
Nerve Fibers ◽  
Lack Of Information ◽  
Lymph Heart ◽  
Muscular Pump ◽  
Structure And Ultrastructure ◽  
Heart Wall

Amphibians have paired muscular pump organs, called “lymph heart”, which rhythmically pump back the lymph from the large subcutaneous lymph sacs into the veins. The structure and ultrastructure of these organs is well known but to date there is a lack of information about the innervation of lymph hearts. Therefore has been carried out an ultrastructural study in order to study the distribution of the nerve fibers, and the morphology of the neuromuscular junctions in the lymph heart wall.

Sign in / Sign up

Export Citation Format

Share Document