Behavioral-Independent Features of Complex Heartbeat Dynamics
Luis A. Nunes Amaral, Plamen Ch. Ivanov, Naoko Aoyagi, Ichiro Hidaka, Shinji Tomono, Ary L. Goldberger, H. Eugene Stanley, Yoshiharu Yamamoto
Abstract
We test whether the complexity of 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.