Nature. 1999 Jun 3;399(6735):461-5.  

Multifractality in human heartbeat dynamics.

Ivanov PC, Amaral LA, Goldberger AL, Havlin S, Rosenblum MG, Struzik ZR, Stanley
HE.

Center for Polymer Studies and Department of Physics, Boston University,
Massachusetts 02215, USA. plamen@buphy.bu.edu

There is evidence that physiological signals under healthy conditions may have a
fractal temporal structure. Here we investigate the possibility that time series
generated by certain physiological control systems may be members of a special
class of complex processes, termed multifractal, which require a large number of
exponents to characterize their scaling properties. We report on evidence for
multifractality in a biological dynamical system, the healthy human heartbeat,
and show that the multifractal character and nonlinear properties of the healthy
heart rate are encoded in the Fourier phases. We uncover a loss of
multifractality for a life-threatening condition, congestive heart failure.

PMID: 10365957 [PubMed - indexed for MEDLINE]