ECG-Derived Sympathetic and Parasympathetic Nervous System Dynamics: A Congestive Heart Failure Study

Spectral analysis of heart rate variability (HRV) has provided a very successful characterization of the autonomic influence on the heart. However, the definition of simple subdivisions in frequency ranges does not fully reflect separate influences of the sympathetic and parasympathetic peripheral outflow because of their simultaneous action in the LF band (0.04-0.15Hz). To overcome this limitation, we recently proposed a methodological framework defining the Sympathetic Activity Index (SAI) and the Parasympathetic Activity Index (PAI), which have been proven effective in characterizing healthy cardiac dynamics. In this study, we aim to evaluate SAI and PAI performances in Congestive Heart Failure (CHF). We estimate normalized SAI and PAI indices on HRV series from Physionet recordings, i.e., 14 CHF patients and 16 healthy controls (CNT). Results show a characteristic increase of the sympathetic dynamics in CHF with respect to CNT despite the significant reduction of HRV spectral power associated with CHF. Results also highlight a significantly reduced vagal activity in CHF with respect to CNT. This study demonstrates the reliability of the proposed measures for a non-invasive autonomic assessment in CHF without the need of model calibration at the individual level.