Comprehensive model for the simulation of left ventricle mechanics

A comprehensive numerical model, based on the finite-element method, for the continuous simulation of the complete cardiac cycle is presented. The model uses real, measuredin vivo, three-dimensional geometry of the ventricle, and accounts for the anisotropy of the ventricular wall, the large deformations it undergoes during the cardiac cycle, the material nonlinearity of the myocardium and its mechanical activation. The simulation process is carried out incrementally while adjusting the mechanical activation for each increment so as to produce the same change in cavity volume as that measured experimentally. A detailed analysis of a complete cycle of the canine heart is presented in Part 2 of the paper.     

Mechanical model for the simulation of ischaemia and infarction of the left ventricle

Several ischaemic states, including immediate infarction, occurring in a canine left ventricle at the onset of the ejection phase and affecting regions of varying sizes are simulated, employing a recently developed comprehensive finite-element model. The analysis assumes an instantaneous partial or complete loss of contractility in the damaged region, whereas the passive mechanical properties of the tissue are yet unaltered. The results indicate a progressive deterioration of the cardiac performance, as well as considerable geometrical changes in the kinematics of the whole ventricle, directly related to both ischaemia level and the ischaemic region size. Owing to the reduction in the stroke volume, the simulation predicts a degradation of up to 33 per cent in the ejection fraction for an infarct affecting 43 per cent of the ventricular wall volume. A quantitative relationship between the ejection fraction, the level of ischaemia and the size of the ischaemic zone is derived and presented.