Studying the influence of hydrogel injections into the infarcted left ventricle using the element‐free Galerkin method

Abstract

Myocardial infarction is an increasing health problem worldwide. Because of an under-supply of blood, the cardiomyocytes in the affected region permanently lose their ability to contract. This in turn gradually weakens the overall heart function. A new therapeutic approach based on the injection of a gel into the infarcted area aims to support the healing and to inhibit adverse remodelling that can lead to heart failure. A computational model is the basis for obtaining a better understanding of the heart mechanics, in particular, how myocardial infarction and gel injections affect its pumping performance. A strain invariant-based stored energy function is proposed to account for the passive mechanical behaviour of the model, which also makes provision for active contraction. To incorporate injections an additive homogenization approach is introduced. The numerical framework is developed using an in-house code based on the element-free Galerkin method. The main focus of this contribution is to investigate the influence of gel injections on the mechanics of the left ventricle during the diastolic filling and systolic isovolumetric (isochoric) contraction phases. It is found that gel injections are able to reduce the elevated fibre stresses caused by an infarct.

Model-Based Assessment of Elastic Material Parameters in Rheumatic Heart Disease Patients and Healthy Subjects

“…In this study, the mechanical model proposed by Usyk et al [23] and reformulated in terms of the invariants of the Green strain tensor, E, by Legner et al [26] was considered for our human biventricular models. The model describes the myocardium as a nonlinear, orthotropic, and nearly incompressible hyperelastic material using the strain energy function given by:…”

“…In terms of the Dirichlet boundary conditions, the ventricles were fixed at the base as shown in Figure 2A to prevent the heart from undergoing rigid body motion in the vertical direction and to allow for the connections between the base and the major blood vessels. The heart experiences a degree of twist during muscular contraction; to allow for this torsional behavior, but still restrict the deformation to a physiologically normal level, another Dirichlet boundary condition was weakly imposed through the application of an elastic line force with spring constant k = 0.1 kN/mm acting in the tangential direction around the epicardial base, as seen in Figure 2B [26,27]. The elastic line forces effectively prevent rigid body motion in the short axis direction, but do not obstruct ventricular wall thickening.…”

Personalised computational cardiology: Patient-specific modelling in cardiac mechanics and biomaterial injection therapies for myocardial infarction

“…Material injections that result in increased stiffness to the infarct region have also been shown to lower stresses in the infarcted and healthy regions of the heart in subject-specific ovine LV FE models [ 67 ] (Fig. 4 ) and for idealised ellipsoid LV models [ 96 ]. Improvements to cardiac function seen in the subject-specific ovine FE model such as wall thickening and increased ejection fraction [ 67 ] are consistent with in vitro and in vivo experiments [ 97 ].…”

Influence of Supraphysiologic Biomaterial Stiffness on Ventricular Mechanics and Myocardial Infarct Reinforcement

“…[10] Computer simulations and finite element analyses have demonstrated that biomaterial stiffness, degradation, and injection location can significantly alter efficacy of therapy. [9, 13,14] Matsumura and colleagues recently were the first to demonstrate efficacy of a synthetic biomaterial, utilizing a relatively stiff (275kPA) material. [15] Synthetic materials have numerous advantages, including the ability to tune material degradation and stiffness properties.…”