Extended Parabolic Phase Space Mapping (EPPSM): Novel quadratic function for representation of Heart Rate Variability signal

In this paper, Extended Parabolic Phase Space Mapping (EPPSM) is introduced. This mapping is a novel method for representation of heart rate which is obtained using RR interval time series signal consist of all the ordered pairs: (RR_i,(RR̅ - RR_i)²), i = 1, ..., N - 1 where RR̅ is the mean of RR intervals. By analyzing the point´s distribution in this map, we could estimate a two degree polynomial equation in the form of y = Ax² + Bx + C in which y is (RR̅ - RR_i)² and x is RR_i. The useful features obtaining of this map are the coefficients A, B, and C. These features were evaluated in distinguishing four groups of subjects (Arrhythmia, Congestive Heart Failure (CHF), Atrial Fibrillation (AF) and Normal Sinus Rhythm (NSR)) obtained of Physionet database. Kruskal-Wallis test was used to define the level of significance of each feature. The results show that these features discriminate CHF from NSR by p<;E-5; arrhythmia from NSR by p<;E-7; and AF from NSR by p<;E-6.