Does the complexity of heartbeat dynamics depend solely on physical activity and behavior, or is it intrinsic and modulated by the autonomic nervous system in healthy adults?
Heartbeat complexity is not merely a consequence of physical activity but is an intrinsic property that decreases with neuroautonomic blockade.
We test whether the complexity of the cardiac interbeat interval time series is simply a consequence of the wide range of scales characterizing human behavior, especially physical activity, by analyzing data taken from healthy adult subjects under three conditions with controls: (i) a "constant routine" protocol where physical activity and postural changes are kept to a minimum, (ii) sympathetic blockade, and (iii) parasympathetic blockade. We find that when fluctuations in physical activity and other behavioral modifiers are minimized, a remarkable level of complexity of heartbeat dynamics remains, while for neuroautonomic blockade the multifractal complexity decreases.
Amaral et al. (Fri,) studied this question.