Efficient identification of myocardial material parameters and the stress-free reference configuration for patient-specific human heart models

Abstract

Image-based computational models of the heart represent a powerful tool to shed new light on the mechanisms underlying physiological and pathological conditions in cardiac function and to improve diagnosis and therapy planning. However, in order to enable the clinical translation of such models, it is crucial to develop personalized models that are able to reproduce the physiological reality of a given patient. There have been numerous contributions in experimental and computational biomechanics to characterize the passive behavior of the myocardium. However, most of these studies suffer from severe limitations and are not applicable to high-resolution geometries. In this work, we present a novel methodology to perform an automated identification of in vivo properties of passive cardiac biomechanics. The highly-efficient algorithm fits material parameters against the shape of a patient-specific approximation of the end-diastolic pressurevolume relation (EDPVR). Simultaneously, a stress-free reference configuration is generated, where a novel fail-safe feature to improve convergence and robustness is implemented. Only clinical image data or previously generated meshes at one time point during diastole and one measured data point of the EDPVR are required as an input. The proposed method can be straightforwardly coupled to existing finite element (FE) software packages and is applicable to different constitutive laws and FE formulations. Sensitivity analysis demonstrates that the algorithm is robust with respect to initial input parameters.

Dyssynchronous Left Ventricular Activation is Insufficient for the Breakdown of Wringing Rotation

“…Since the LV is under constant stress due to the flow of blood, we have to find a suitable initial stress distribution. Therefore, we first find a stress-free state of the LV by solving an inverse elasto-static problem as described in Marx et al (2021) . Then, the stress-free configuration is inflated with a pressure p LV = 8 mmHg by solving the static problem to find the displacement u .…”

An accurate, robust, and efficient finite element framework for anisotropic, nearly and fully incompressible elasticity

“…First, initial passive material parameters above were fitted to the empiric description of the EDPVR by Klotz et al [95]. For each element type we used a backward displacement algorithm and boundary conditions replicating experiments in [95] according to Marx et al [96], see Figure 10. This fitting resulted in multiplicative scaling factors of 0.4529 (P1-P0 elements) and 0.9582 (locking-free elements) for the stresslike material parameters (a, a f , a s , a fs ); and in multiplicative scaling factors of 1.0322 (P1-P0 elements) and 0.7981 (locking-free elements) for the dimensionless parameters (b, b f , b s , b fs ).…”