Distribution of normal human left ventricular myofiber stress at end diastole and end systole: a target for in silico design of heart failure treatments

Abstract

Ventricular wall stress is believed to be responsible for many physical mechanisms taking place in the human heart, including ventricular remodeling, which is frequently associated with heart failure. Therefore, normalization of ventricular wall stress is the cornerstone of many existing and new treatments for heart failure. In this paper, we sought to construct reference maps of normal ventricular wall stress in humans that could be used as a target for in silico optimization studies of existing and potential new treatments for heart failure. To do so, we constructed personalized computational models of the left ventricles of five normal human subjects using magnetic resonance images and the finite-element method. These models were calibrated using left ventricular volume data extracted from magnetic resonance imaging (MRI) and validated through comparison with strain measurements from tagged MRI (950 ± 170 strain comparisons/subject). The calibrated passive material parameter values were C0 = 0.115 ± 0.008 kPa and B0 = 14.4 ± 3.18; the active material parameter value was Tmax = 143 ± 11.1 kPa. These values could serve as a reference for future construction of normal human left ventricular computational models. The differences between the predicted and the measured circumferential and longitudinal strains in each subject were 3.4 ± 6.3 and 0.5 ± 5.9%, respectively. The predicted end-diastolic and end-systolic myofiber stress fields for the five subjects were 2.21 ± 0.58 and 16.54 ± 4.73 kPa, respectively. Thus these stresses could serve as targets for in silico design of heart failure treatments.

A Novel Method for Quantifying Smooth Regional Variations in Myocardial Contractility Within an Infarcted Human Left Ventricle Based on Delay-Enhanced Magnetic Resonance Imaging

“…For example, the myocardial stiffness of C 0 ¼ 0:102 kPa found using our method is very close to the range of normal human stiffness characterized in Ref. [14], i.e., 0:105 À 0:123 kPa (mean 6 standard deviation: 0:115 6 0:00817 kPa). Similarly, the calculated remote myocardial contractility of T max ¼ 146:9 kPa is inside the range of normal human contractility characterized in Ref.…”

“…We start by briefly describing our LV finite-element modeling framework, emphasizing the improvement with regard to the previous work from our group [4,[12][13][14].…”

“…We consider here the values defined in Ref. [14] for normal humans, shown in Table 1. The law has another parameter, C 0 , which scales the stiffness of the material, and usually needs to be personalized for each patient.…”

“…b f , b t , and b ft define the material anisotropy, values established in Ref. [14] for normal humans are considered here. parameter for the material behavior away from the infarct.…”

“…More details on the formulation and the definition and values of the parameters, can be found in Refs. [4,[12][13][14]. The parameter T max scales the tissue contractility and, similar to C 0 for the passive law, needs to be personalized for each patient.…”