Spiral Wave Initiation in an Electromechanical Model for Human Cardiac Tissue

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Heart failure due to cardiac arrhythmias is a major cause of death in the industrialized world. Dangerous types of arrhythmia are caused by spiral waves of electrical activity in the cardiac muscle. Therefore, it is a major task in cardiology to understand mechanisms of spiral wave initiation in the heart.Most previous theoretical studies on spiral wave initiation in the heart did not take the deformation of the heart into account; albeit, the mechanical activity of the heart has been shown to greatly affect the electrical processes.In my PhD thesis I have developed a new modeling framework to study electromechanical activity of cardiac tissue. It couples a simplified model for cardiac excitation with a discrete mechanical description of cardiac elasticity. This model provides an efficient numerical framework to study generic properties of electromechanical processes in cardiac tissue. I used the method to systematically study the basic mechanisms of spiral wave initiation that emerge as a consequence of the complex coupling of the electrical and mechanical processes in the heart. This research delivered promising results: I was able to identify five mechanisms of spiral formation that could occur in the heart.A limitation of that previous work is that my approach does not describe the ionic currents of a cardiac cell and its processes of tension development in detail, but rather employs a generic description. Therefore, I have started to develop of a new model which combines my efficient discrete mechanics model to biophysical models of human cardiac excitation and excitation-contraction coupling.The aim of this project is to use my new approach and determine which of the previously found mechanisms for spiral wave initiation are relevant for human cardiac tissue, and also, identification of new biophysical mechanisms of onset of cardiac arrhythmias. First preliminary results indicate that such new mechanisms are likely to be found. My recent simulations showed that deformation of the heart may promote dynamical instabilities - cardiac alternans - which are considered in experimental, modeling and even clinical work, as predictors for the onset of arrhythmias.