Postischemic ventricular function of stunned myocardium: A modeling perspective

Myocardial stunning is a prolonged postischemic dysfunction that compromises ventricular performance. Several contributing factors have been identified, but the exact mechanism of myocardial stunning remains unclear. A computer model of the ventricle can be effective in modeling the dominant observable features of myocardial stunning. A regional ventricular model is first introduced here, followed by a single cardiac muscle fiber model. The regional model is based on a previously developed multicompartment model with normal and ischemic zones incorporating time-varying elastance and viscoelastic properties. The mathematical model of the single cardiac muscle fiber consisted of three elements: a contractile element, a series elastic element, and a parallel elastic element. On the basis of the classic force-velocity-length relations, the single muscle model could generate muscle length waveforms based on time-dependent force and contractile stiffness functions. By entering the same parameter values used in the regional ventricular model, and by reducing contractile stiffness function or the rates of activation and deactivation, the three-element model could mimic similar results observed in canine experiments.