A Novel Method for Quantifying the In-Vivo Mechanical Effect of Material Injected Into a Myocardial Infarction

Abstract

Infarcted regions of myocardium exhibit functional impairment ranging in severity from hypokinesis to dyskinesis. We sought to quantify the effects of injecting a calcium hydroxyapatite-based tissue filler on the passive material response of infarcted left ventricles. Three-dimensional (3D) finite element models of the left ventricle were developed using 3D echocardiography data from sheep with a treated and untreated anteroapical infarct, in order to estimate the material properties (stiffness) in the infarct and remote regions. This was accomplished by matching experimentally determined left ventricular volumes, and minimizing radial strain in the treated infarct, which is indicative of akinesia. The nonlinear stress-strain relationship for the diastolic myocardium was anisotropic with respect to the local muscle fiber direction, and an elastance model for active fiber stress was incorporated. It was found that the passive stiffness parameter, C, in the treated infarct region is increased by nearly 345 times the healthy remote value. Additionally, the average myofiber stress in the treated left ventricle was significantly reduced in both the remote and infarct regions. Overall, injection of tissue filler into the infarct was found to render it akinetic and reduce stress in the left ventricle, which could limit the adverse remodeling that leads to heart failure.

Injection of Peptide Nanogels Preserves Postinfarct Diastolic Function and Prolongs Efficacy of Cell Therapy in Pigs

“…It is probably because the benefits of material injection are due to passively providing mechanical support. [35][36][37][38] To truly improve cardiac systolic function and pumping ability, it relies on either directly implanting constructs with actively contractive cells [38][39][40][41] or indirectly reducing loss of host cardiomyocytes by angiogenesis or paracrine effects from biological substance. 42,43 We previously showed angiogenesis was induced by MNC transplantation with/without NFs at 1 month post-MI.…”

A computational model that predicts reverse growth in response to mechanical unloading

“…For example, a significant reduction in the left ventricular size (up to 50 %) was observed in patients who underwent bioinjection treatment with Algiysl-LVR, a calcium-sodium-alginate hydrogel proprietary to Lonestar Heart, Inc (Lee et al 2013). This treatment was associated with a decrease in end-diastolic myofiber stress (Wenk et al 2011) and a leftward shift in end-diastolic pressure–volume relationship (Wall et al 2006). Reverse geometrical remodeling of the left ventricle was also observed after mitral valve repair, which decreases preload (Brinke et al 2010).…”

A numerical study of a heart phantom model

“…For example, Guccione et al found that myocardial contractility in the infarct border zone is significantly reduced yet associated with elevated myofibre stress, which predisposes to heart failure in the longer term [13,[35][36][37]. Veress et al [32] simulated normal and abnormal motions of the LV using a physiologically based, FE mechanical model, with the aim to enhance the 4-D NURBS-based NCAT phantom.…”