Application of Methods from Nonlinear Dynamics for Heart Rate Variability Analysis

The article presents the results of the study of the nonlinear properties of the dynamics of the intervals between heartbeats obtained from digital ECG signals of healthy subjects, patients with arrhythmia and patients with heart failure. Data analysis was performed by applying the following two methods of nonlinear dynamics: Recurrence plot and Poincaré plot, comparing with the linear histogram method. The visual evaluation of the repeating diagrams constructed by the Recurrence plot allows obtaining quick information about the behaviour of the studied process. The reduction of the complexity of the process (heart rhythm) and the transition to periodicity is indicative of a pathological change in the regulation of heart rhythm. Poincaré plot is a useful tool when rare and sudden disorders occur against the background of a monotonous heart rate. Cardiovascular diseases significantly affect the dynamics of heart rate, reducing variability.