Real time control of a period doubling bifurcation in frog hearts.

Arrhythmia, irregular heartbeats caused by disorganized firing of impulses, is the largest contributor to heart disease, the leading cause of death in the US and other industrialized countries. T-wave alternans (TWA) are a promising electrocardiogram index of ventricular arrhythmic susceptibility that involves measuring beat-to-beat variation in electrocardiogram T-waves (which correspond to ventricular repolarization). It has been shown that TWA is originated by a period doubling bifurcation when cardiac tissue is paced at fast constant cycle lengths. The bifurcation can be explained theoretically via linear stability analysis of a physiological adaptation function that can be calculated experimentally. In this study, we measure the adaptation function and use this theory to test a real time control method, that has been tested with numerical models, in the frog hearts. In this talk I will describe the theory behind the bifurcation, the real time control method and system we have developed for it as well as experimental results. With this work we aim to provide insight into future technologies for arrhythmia prevention in humans.