Fig. 1

Schematic representation of heart rate asymmetry algorithms. Blue dots show points in the Poincaré plot. P _i is the ith point which can be denoted by \( (RR_{i} ,RR_{i + 1} ),\Delta RR = RR_{i + 1} - RR_{i} \). LI is the line of identity. a \( R\theta_{i} \) is the phase angle of the P _i respect to LI. Filled areas are the sectors we used in AI; b. D _i is the distance of P _i to LI and \( \theta_{i} \) the phase angle of P _i respect to the abscissa; \( \theta_{LI} \) is the phase angle of LI