Georgia Institute of Technology College of Sciences

The heart is an excitable system in which electrical waves normally propagate in a coordinated manner to produce an effective mechanical contraction. Rapid pacing can lead to the development of alternans, a period-doubling bifurcation in electrical response in which successive beats have long and short responses despite a constant pacing period. Alternans can develop into higher-order rhythms as well as spatiotemporally complex patterns that reflect large regions of dispersion in electrical response. These states disrupt synchrony and compromise the heart's mechanical function; indeed, alternans has been observed clinically as a precursor to dangerous arrhythmias, including ventricular fibrillation. In this talk, we will show experimental examples of alternans, describe how alternans develops using a mathematical and computational approach, and discuss the nonlinear dynamics of several possible mechanisms for alternans as well as the conditions under which they are likely to be important in initiating dangerous cardiac arrhythmias.