Application of an ellipsoidal heart model in studying left ventricular contractions

A geometrical model for the left ventricle is developed consisting of a nested set of truncated ellipsoidal shells of revolution. The geometrical parameters are modelled with the aid of measuring data and assumptions about ventricular deformation. The shells contain muscle fibres which generate wall tension (according to a muscle model previously described), from which ventricular pressure results. Fibre length and orientation have different values per shell. After ventricular deformation (change in preload, ejection) new values of the length and orientation can be calculated. The geometrical aspects of the model were tested with literature data. Apart from the apical region the results appear to be satisfactory. Calculated fibre lengths over the wall agree reasonably with measured data, if rather realistic ventricular shape changes were applied. The mechanical aspects (pressure generation, developed flow) were also tested with experiments on rabbit hearts. They agree with previous results obtained from a cylindrical model