M Nash [Auckland]
Tuesday 21st July 2009 -
14:30 to 14:45
INI Seminar Room 1
Cardiac Electro-Mechanical Coupling
We present an integrative 3D electro-mechanical model of the human heart ventricles (RVLV), constructed from diffusion tensor magnetic resonance imaging data provided by Drs Helm, Winslow and McVeigh (Johns Hopkins University and NIH). Mathematical models of electrical activity (TNNP) and contractile tension (NHS) of cardiac myocytes are coupled within a transversely isotropic passive mechanical (Guccione) constitutive framework embedded within the RVLV model. Excitation-contraction coupling is achieved via the intracellular calcium concentration of the biophysical myocyte models. Mechano-electrical feedback is represented by stretch-activated channels, which carry currents that are modulated by local deformation. Numerical model integration combines an explicit finite differences scheme for the electrophysiology with a non-linear finite element method for the mechanics. The model was tuned and verified by simulating a normal ventricular cycle and comparing the resulting myocardial strain distributions with experimental recordings. This human RVLV model was used to investigate the effects of mechano-electrical feedback on re-entrant wave dynamics. We examine factors that cause wavebreak and the degeneration of stable re-entry into fibrillatory activity. We identify the mechanisms of this transition to VF, and study the 3D organisation of mechanically induced VF in the human heart.