SIMULATION OF THE STATIC INFLATION OF THE PASSIVE LEFT VENTRICLE TO AN END-DIASTOLIC STATE

To initiate our simulations of canine left ventricle (LV) mechanics, we needed to specify an initial geometry and an initial wall stress distribution. Although there are sufficient measurements of LV geometries, there are no assessments of stresses under any conditions. To estimate a physiologically plausible range of stresses at end diastole, we have inflated an unloaded reference geometry using static pressure loads. The LV was modelled as a six-layered truncated prolate ellipsoid. The myocardium was defined as a slightly compressible, transversely isotropic, hyperelastic material. The reference LV was inflated statically by gradually increasing the pressure on its inner surface until an end-diastolic state was reached. The calculated dependence of normalized LV volume changes on the applied pressure was in good agreement with previous experimental results. Our calculated geometry was found to be comparable to previous measurements. The end-diastolic stresses were found to have complex variations, which cannot be determined by adopting an ad hoc stress-free, end-diastolic geometry. The calculated geometry and stress distribution are deemed to be suitable for use as initial states for cardiac cycle simulations.