Computing Work in the Ischemic Heart

This study analyzes the effect of a poorly perfused (ischemic) region on active tension and strain at a point in a model of the cardiac ventricles. The cellular active mechanics and electrophysiology were calculated using a coupled electromechanical cell model. The deformation of the heart was calculated combining an anisotropic constitutive law with the active tension generated by the cell models. An ischemic cell model was developed by adapting the Noble 98-HMT cell model parameters. The ischemic model exhibits a raised resting potential, shortened action potential duration and reduced amplitude. Ischemic cells were introduced into the heart model in the anterior wall of the left ventricle. The model was solved with and in the absence of the ischemic region. The stress and strains at a point located in the ischemic region were calculated. The ischemic cell model produced negligible amounts of active tension and this reduced the work load of ischemic cells by several orders of magnitude. The ischemic region had a significant effect on pump function in both the left and right ventricles.