Finite-element based optimization of left ventricular passive stiffness in normal volunteers and patients after myocardial infarction: Utility of an inverse deformation gradient calculation of regional diastolic strain

Introduction: Left ventricular (LV) diastolic dysfunction (DD) is common after myocardial infarction (MI). Whereas current clinical assessment of DD relies on indirect markers including LV filling, finite element (FE) -based computational modeling directly measures regional diastolic stiffness. We hypothesized that an inverse deformation gradient (DG) method calculation of diastolic strain (IDGDS) allows the FE model-based calculation of regional diastolic stiffness (material parameters; MP) in post-MI patients with DD. Methods: Cardiac magnetic resonance (CMR) with tags (CSPAMM) and late gadolinium enhancement (LGE) was performed in 10 patients with post-MI DD and 10 healthy volunteers. The 3-dimensional (3D) LV DG from enddiastole (ED) to early diastolic filling (EDF; DGED -> EDF) was calculated from CSPAMM. Diastolic strain was calculated from DGEDF -> ED by inverting the DGED -> EDF. FE models were created with MI and non-MI (remote; RM) regions determined by LGE. Guccione MPs C, and exponential fiber, bf, and transverse, bt , terms were optimized with IDGDS strain. Results: 3D circumferential and longitudinal diastolic strain (Ecc; Ell) calculated using IDGDS in CSPAMM obtained in volunteers and MI patients were EccH = 0.27 +/- 0.01, Ell H = 0.24 +/- 0.03 and EccMI = 0.21 +/- 0.02, and Ell MI = 0.15 +/- 0.02, respectively. MPs in the volunteer group were CH = 0.013 [0.001, 0.235] kPa, bfH = 20.280 +/- 4.994, and btH = 7.460 +/- 2.171 and CRM = 0.0105 [0.010, 0.011] kPa, bf RM = 50.786 +/- 13.511 (p = 0.0846), and bt RM = 17.355 +/- 2.743 (p = 0.0208) in the remote myocardium of post-MI patients. Conclusion: Diastolic strain, calculated from CSPAMM with IDGDS, enables calculation of FE model-based regional diastolic material parameters. Transverse stiffness of the remote myocardium, bt RM, may be a valuable new metric for determination of DD in patients after MI.

Automated summary

A novel method was used in this study to directly measure regional diastolic stiffness in patients after myocardial infarction, which may aid in diagnosing left ventricular diastolic dysfunction. The results showed that using this method, it is possible to calculate diastolic material parameters in different areas of the heart, which helps to more accurately assess the cardiac health status of patients.