Multifractality in human heartbeat dynamics

There is evidence that physiological signals under healthy conditions may h ave a fractal temporal structure(1). Here we investigate the possibility th at time series generated by certain physiological control systems may be me mbers of a special class of complex processes, termed multifractal, which r equire a large number of exponents to characterize their scaling properties (2-6). We report on evidence for multifractality in a biological dynamical system, the healthy human heartbeat, and show that the multifractal charact er and nonlinear properties of the healthy heart rate are encoded in the Fo urier phases. We uncover a loss of multifractality for a life-threatening c ondition, congestive heart failure.