MODELING OF MECHANICAL DYSFUNCTION IN REGIONAL STUNNED MYOCARDIUM OF THE LEFT-VENTRICLE

Reversible mechanical dysfunction of the myocardium after a single or multiple episode(s) of coronary artery occlusion has been observed in previous studies and is termed myocardial stunning, The hypothesis tha t stunning could be represented by a decrease in maximum available mus cle force in the stunned region was examined by means of a mathematica l model that incorporates series viscoelastic elements, A canine exper imental model was also employed to demonstrate depressed contractility and a consistent delay of shortening in the stunned region, The mecha nical model of the left ventricle was designed to include a normal and stunned region, for which the stunned region was allowed to have vari able size, Each region consisted of a volume and time dependent force generator in parallel with a passive elastic force element, The passiv e elastic element was placed in series with a constant viscosity compo nent and a series elastic component. The model was solved by means of a computer, Passive and active properties of each region could be alte red independently, The typical regional measures of muscle performance such as percent shortening, percent bulge, percent thickening, delay of shortening, percent increase in end-diastolic length and other hemo dynamic measures were computed, These results were similar to those ob served in animal models of stunning, In addition, a nearly linear rela tionship with end-diastolic length and delay of shortening was predict ed by the model, It was concluded that a decrease in the peak isovolum ic elastance and augmentation of viscosity effect of creep during stun ning can explain mechanical abnormalities of stunned myocardium.