Scale invariance in the nonstationarity of human heart rate - art. no. 168105

We introduce a segmentation algorithm to probe the temporal organization of heterogeneities in human heartbeat interval time series. We find that the lengths of segments with different local mean heart rates follow a power-la w distribution and show that this scale-invariant structure is not a simple consequence of the long-range correlations present in the data. The differ ences in mean heart rates between consecutive segments display a common fun ctional form, but with different parameters for healthy individuals and for heart-failure patients. These findings suggest that there is relevant phys iological information hidden in the heterogeneities of the heartbeat time s eries.