RESUMEN
We analyze RR heartbeat sequences with a dynamic model that satisfactorily reproduces both the long- and the short-time statistical properties of heart beating. These properties are expressed quantitatively by means of two significant parameters, the scaling delta concerning the asymptotic effects of long-range correlation, and the quantity 1-pi establishing the amount of uncorrelated fluctuations. We find a correlation between the position in the phase space (delta, pi) of patients with congestive heart failure and their mortality risk.
Asunto(s)
Biofisica/métodos , Insuficiencia Cardíaca/mortalidad , Insuficiencia Cardíaca/fisiopatología , Fenómenos Fisiológicos Cardiovasculares , Cardiopatías/fisiopatología , Frecuencia Cardíaca , Humanos , Modelos Biológicos , Modelos Estadísticos , Análisis Multivariante , Dinámicas no Lineales , Riesgo , Procesamiento de Señales Asistido por Computador , Análisis de Supervivencia , Sístole , TiempoRESUMEN
We describe two types of memory and illustrate each using artificial and actual heartbeat data sets. The first type of memory, yielding anomalous diffusion, implies the inverse power-law nature of the waiting time distribution and the second the correlation among distinct times, and consequently also the occurrence of many pseudoevents, namely, not genuinely random events. Using the method of diffusion entropy analysis, we establish the scaling that would be determined by the real events alone. We prove that the heart beating of healthy patients reveals the existence of many more pseudoevents than in the patients with congestive heart failure.
Asunto(s)
Frecuencia Cardíaca/fisiología , Memoria/fisiología , Simulación por Computador , Electrocardiografía/estadística & datos numéricos , Entropía , Insuficiencia Cardíaca/fisiopatología , Humanos , Modelos EstadísticosRESUMEN
We study the entropy time evolution of a quantum mechanical model, which is frequently used as a prototype for Anderson's localization. Recently Latora and Baranger [Phys. Rev. Lett. 82, 520 (1999)] found that there exist three entropy regimes, a transient regime of passage from dynamics to thermodynamics, a linear-in-time regime of entropy increase, that is, a thermodynamic regime of Kolmogorov kind, and a saturation regime. We use the nonextensive entropic indicator advocated by Tsallis [J. Stat. Phys. 52, 479 (1988)] with a mobile entropic index q, and we find that the adoption of the "magic" value q=Q=1/2, compared to the traditional entropic index q=1, reduces the length of the transient regime and makes earlier the emergence of the Kolmogorov regime. We adopt a two-site model to explain these properties by means of an analytical treatment and we argue that Q=1/2 might be a typical signature of the occurrence of Anderson localization.