A computationally efficient formal optimization of regional myocardial contractility in a sheep with left ventricular aneurysm

A noninvasive method for estimating regional myocardial contractility in vivo would be of great value in the design and evaluation of new surgical and medical strategies to treat and/or prevent infarction-induced heart failure. As a first step toward developing such a method, an explicit finite element (FE) model-based formal optimization of regional myocardial contractility in a sheep with left ventricular (LV) aneurysm was performed using tagged magnetic resonance (MR) images and cardiac catheterization pressures. From the tagged MR images, three-dimensional (3D) myocardial strains, LV volumes, and geometry for the animal-specific 3D FE model of the LV were calculated, while the LV pressures provided physiological loading conditions. Active material parameters (T_max-B and T_max-R) in the noninfarcted myocardium adjacent to the aneurysm (border-zone) and in the myocardium remote from the aneurysm were estimated by minimizing the errors between FE model-predicted and measured systolic strains and LV volumes using the successive response surface method for optimization. The significant depression in optimized T _max-B relative to T_max-R was confirmed by direct ex vivo force measurements from skinned fiber preparations. The optimized values of T_max-B and T_max-R were not overly sensitive to the passive material parameters specified. The computation time of less than 5 h associated with our proposed method for estimating regional myocardial contractility in vivo makes it a potentially very useful clinical tool.