Recurrence Analysis of Cardiac Restitution in Human Ventricle

The cardiac restitution curve describes functional relationships between diastolic intervals and their corresponding action potential durations. Although the simplest relationship is that restitution curves are monotonic, empirical studies have suggested that cardiac patients present a more complex dynamical process characterized, for instance, by a non-monotonic restitution curve. The purpose of this chapter is to analyze the dynamical properties of a non-monotonic cardiac restitution curve model derived from previously published clinical data. To achieve this goal, we use Recurrence Quantitative Analysis combined with Lyapunov exponents and Supertrack Functions in order to describe the complex dynamics underlying non-monotonic restitution curves. We conclude by highlighting that a consequence of the advanced complex dynamics that emerges from the aforementioned non-monotonicity, is the increasing risk of alternant rhythms.