Neurohormonal and functional correlates of linear and poincarè plot indexes of heart rate variability in heart failure patients

Higher neurohormonal activation levels are known markers of severity in heart failure (HF). Aim of the study was to assess the association of Poincarè plot indexes (PPI) of RR time series with plasma norepinephrine (NPE) levels and functional parameters as compared to classical linear indexes of HRV. Ninety-nine HF patients underwent to a 24-hour Holter recording and a standard clinical and laboratory examinations included plasma NPE assay. The SDNN and the power in the low frequency band were computed. PPI were obtained by automated quantification of the bi-dimensional length, L and tri-dimensional (peak's number Np, radii of the semiellipse of inertia Px, Py, Pz morphological characteristics. Both SDNN and LFP showed a moderate but significant negative correlation with NPE levels while a weaker association was found for L, Np and Py. Linear indexes were significantly associated with VO2max and between PPI similar correlation were found for L, Py and Pz. Similar relationships were found with EF for SDNN, LFP, L, Np, Pz, with a negative correlation for Px. These findings suggest that although the association of linear and PPI of HRV with functional parameters is similar, the former, particularly the power in the low frequency band, appear to reflect more closely the level of adrenergic activation of HF patients.