In vivo estimation of passive biomechanical properties of human myocardium

Identification of in vivo passive biomechanical properties of healthy human myocardium from regular clinical data isessential for subject-specific modelling of left ventricle (LV). In this work, myocardium was defined by HolzapfelOgden constitutive law. Therefore, the objectives of the study were (a) to estimate the ranges of the constitutiveparameters for healthy human myocardium using non-invasive routine clinical data, and (b) to investigate the effectof geometry, LV end-diastolic pressure (EDP) and fibre orientations on estimated values. In order to avoid invasivemeasurements and additional scans, LV cavity volume, measured from routine MRI, and empirical pressure-normalisedvolume relation (Klotz-curve) were used as clinical data. Finite element modelling, response surface method and geneticalgorithm were used to inversely estimate the constitutive parameters. Due to the ill-posed nature of the inverse optimisation problem, the myocardial properties was extracted by identifying the ranges of the parameters, instead of findingunique values. Additional sensitivity studies were carried out to identify the effect of LV EDP, fibre orientation andgeometry on estimated parameters. Although uniqueness of the solution cannot be achieved, the normal ranges of theparameters produced similar mechanical responses within the physiological ranges. These information could be used infuture computational studies for designing heart failure treatments.