Correlation among Poincare´plot indexes and time and frequency domain measures of heart rate variability

Primary objective: In order to corroborate the reported performance advantage of Poincar´eplot indexes as autonomic activity markers, the correlation among these indexes and those computed from the time and frequency domains were obtained. Methods and procedures: Starting from the RR series derived from the ECG of 21 healthy volunteers during five manoeuvres, longitudinal (L), transverse (T) axis, and autocorrelation (r) from Poincar´eplots, rMSSD and standard deviation (SD) in the temporal domain, and frequency domain indexes were computed. Main outcomes and results: Poincar´e plot indexes were correlated in a better way with the time indexes, rather than the spectral measures. A strong correlation (0.997) between L and SD was observed, while an underlying mathematical relationship was established for T vs rMSSD. Conclusions: Poincaré plot indexes may be considered as equivalent or surrogates of the temporal ones, and they do not have a better performance as autonomic markers.