School of Physics Thesis Proposal

Presenter:      Mikael Toye

Title:                    Experimental Determination of Chaos in Cardiac Tissue; Period Three, Periodic Orbits, and Unstable Dynamics

Date:                   Tuesday, November 7, 2023

Time:                   1:00 p.m.

Place:               Howey N110

Committee:   Dr. Flavio Fenton, School of Physics, Georgia Institute of Technology (Advisor)

Dr. Predrag Cvitanovic,  School of Physics, Georgia Institute of Technology

Dr. Michael Schatz, School of Physics, Georgia Institute of Technology

Dr. Kurt Wiesenfeld, School of Physics, Georgia Institute of Technology

Abstract:

Experimental Determination of Chaos in Cardiac Tissue; Period Three, Periodic Orbits, and Unstable Dynamics

Many cardiac voltage models predict chaotic dynamics when paced within specific frequency regimes, but are the voltage dynamics of living cardiac tissue actually chaotic? Particularly, during arrhythmias and fibrillation events of living tissue, voltage dynamics do seem to resemble chaos. However, there has been debate whether the voltage dynamics of cardiac tissue and fibrillation are chaotic, stochastic, or some combination of both. If ventricular fibrillation is chaotic, periodic orbit theory and nonlinear control mechanisms could be leveraged to control and treat arrhythmias in medical settings. 

Here, I propose a thesis to give a comprehensive experimental analysis of the possibility of chaos in cardiac voltage dynamics. First, I will build upon previous work on periodically driven single cell cardiac chaos by verifying results and extending them with the estimation of Lyapunov exponents and identification of periodic orbits and the shadowing of periodic orbits in temporal voltage dynamics, measured through microelectrode experiments. Then, I will analyze spatiotemporal data from optical mapping of whole ventricles to quantify and qualify possible chaotic phenomena occurring in periodically paced tissue and ventricular fibrillation. Finally, I will investigate the implication of my results in relation to both nonlinear control of cardiac voltage dynamics, and the comparison of complex dynamics of fibrillation in different species: rabbits, pigs, and humans. My research in these directions has the potential to further the development in understanding chaotic phenomena in cardiac electrophysiology and improve the treatment of cardiac arrhythmias.