Using the models of myocardial material properties obtained from biaxial testing, together with parameter estimation techniques specially developed for the purpose, we then obtain the regional distribution of myocardial stress throughout the heart cycle. The pressure distribution acting on the endocardial surfaces provides the coupling with the model of myocardial mechanics. Mathematical modelling of myocardial activation Many deaths from heart failure are associated with a failure of the heart's conduction system. We are therefore developing mathematical models in order to gain a better understanding of these failures and in particular to identify the location of focal sites of reentrant arrhythmia. The electrical and mechanical aspects of heart function are closely coupled.
Electrical signals initiate mechanical contraction and control the strength of that contraction.
Mechanical deformation in turn alters the pathlengths for electrical propagation and also directly affects the conductance of the ion channels in the cell membranes. This area of research is likely to become a major focus of our work. In a clinical application an array of electrodes is placed around the heart during open heart surgery and the potential measurements are used in conjunction with the mathematical models to locate reentrant pathways and sites of ectopic activity. The results of this work are in use at Green Lane Hospital in Auckland and at Cedars-Sinai Medical Centre in Los Angeles. A new mapping system with up to 4096 electrodes is under construction.