Under healthy conditions, the normal cardiac (sinus) interbeat interval fluctuates in a complex manner. Quantitative analysis using techniques adapted from statistical physics reveals the presence of long-range power-law correlations extending over thousands of heartbeats. This scale-invariant (fractal) behavior suggests that the regulatory system generating these fluctuations is operating far from equilibrium. In contrast, it is found that for subjects at high risk of sudden death (eg, congestive heart failure patients), these long-range correlations break down. Application of fractal scaling analysis and related techniques provides new approaches to assessing cardiac risk and forecasting sudden cardiac death, as well as motivating development of novel physiologic models of systems that appear to be heterodynamic rather than homeostatic
Bibliographical noteFunding Information:
Partial support was provided to Dr. Peng by NIH/NIMH NRSA Postdoctoral Fellowship, to Dr. Hausdorff by NIA, to Drs. Stanley and HavEn by NSF, and to Dr. Goldberger by the G. Harold and Leila Y. Mathers Charitable Foundation, NIDA, and NASA.
- cardiac interbeat interval
- fractal scaling analysis
- sudden cardiac death