Sinoaortic denervation reduces the complexity of heart rate variability in mice

Heart rate variability (HRV) is recognized as a phenomenon highly complex, presenting nonlinear dynamics with fractal correlations and multiscale properties. Several cardiovascular and systemic diseases are related to loss of complexity in HRV, which has been recognized as an independent risk factor for life-threatening cardiovascular outcomes. Considering that most cardiovascular diseases are accompanied by autonomic imbalance and baroreflex dysfunction, we hypothesise that the baroreflex may play an important role in the genesis of HRV complexity. Mice were submitted to sinoaortic denervation (SAD) and received catheters into femoral artery and jugular vein 5 days prior to the experiment. Baseline arterial pressure (AP) was recorded and pulse interval (PI) time series were generated from the intervals between consecutive diastolic pressures. The complexity of the HRV was determined using detrended fluctuation analysis (DFA) and multiscale entropy (MSE). DFA α1 scaling exponent (a short-term index) was remarkably decreased in the SAD mice (0.79±0.06 vs. 1.13±0.04 for the control mice), whereas SAD slightly increased the α2 scaling exponent (a long-term index: 1.12±0.03 vs. 1.04±0.02 from control). In SAD mice, total MSE was decreased (13.2±1.3) compared to the control counterparts (18.9±1.4). In conclusion, both fractal and regularity structures of HRV are altered by SAD in mice, affecting short- and long-term mechanisms of complexity, suggesting that the baroreceptors play a important role in the complex structure of HRV. Finacial Support: FAPESP, CAPES, CNPq