Session S23.1

A Modified FitzHugh-Nagumo Model that Allows Control of Action Potential Upstroke Velocity and Conduction Velocity

J Li*, S Inada, H Dobrzynski, H Zhang, M Boyett

The University of Manchester
Manchester, UK

Many models have been proposed to simulate the cardiac action potential. They can be classified into two groups: biophysically-detailed (ionic) models and mathematical caricatures (simplified models). To investigate complex electrophysiological behaviour (such as reentrant cardiac arrhythmias) in the setting of the complex anatomy of the heart, the use of a simplified model is computationally more effective – it enables testable predictions about heart behaviour to be made with relatively low computational resource requirements. In this study, the Rogers-modified FitzHugh-Nagumo model[1] was further modified to allow control of action potential upstroke velocity, conduction velocity, duration and refractory period. Model parameters were chosen to simulate the action potentials in rabbit sinoatrial node (SAN), atrioventricular node (AVN), atrial muscle and His bundle. When defining model parameters, a 5x5x50 elements model of a strand of SAN, AVN, atrial muscle or His bundle tissue was used. A stimulus was given to the first three sets of elements at one end of the strand (3x5x5). The action potential waveform was recorded from the middle of the strand (point 3, 3, 25). The conduction velocity was measured as the average conduction velocity from the 10th set of elements to the 40th set of elements. Action potential duration was measured at 90% repolarization. A standard S1-S2 protocol was used to measure the refractory period. The resulting action potential waveforms were a reasonable fit to experimental data. We have successfully used the models to simulate normal action potential conduction through our rabbit right atrium model[2] - from the centre of the SAN, the action potential conducted throughout the right atrium and, finally, through the AVN. Using a S1-S2 protocol, we were able to simulate an atrial reentrant arrhythmia -reentry occurred around the superior vena cava and the high frequency activity was filtered by the AVN such that the frequency of action potentials reaching the His bundle was reduced, as observed experimentally. References 1. Rogers JM, McCulloch AD. IEEE Trans. Biomed. Eng. 1994; 41:743-757. 2.Li J et al. Computers in Cardiology 2005; 32:603-606.

(Abstract Control Number: 87)