Breakdown of scaling properties in abnormal heart rate variability

Abstract

The heart rate variability (HRV) of subjects with normal sinus rhythm (NSR) and subjects with congestive heart failure  (CHF) is compared by using a structure function borrowed from turbulence studies. Firstly, it is shown that the HRV of subjects with NSR displays a power law scaling property, which indicates the presence of structured heartbeat control mechanisms. Secondly, it is found that such a scaling property is partially lost for subjects with CHF. The absence of scaling properties is associated to the presence of uncorrelated (i.e., noise-like) heart rate variations. In order to gain insights on the source of the scaling property, the HRV is analyzed from a systemic (i.e., feedback control) viewpoint in the frequency domain. It is found that the HRV of subjects with NSR is governed by a stable adaptive control mechanism presumably located in the autonomic nervous system. In the case of subjects with CHF, the results show that this regulation mechanism is partially or totally absent, which is interpreted as the cause of the breakdown of the scaling law property.