Heart Rate Asymmetry Analysis Using Poincaré Plot

Abstract

Physiological systems are inherently complex and subject to energy, entropy and information fluxes across their boundaries. These systems function in disequilibrium in healthy condition and their self-organizing capability is related to asymmetricity of the underlying processes (Costa et al., Phys. Rev. Lett. 95:1–4, 2005). In pathological perturbations, a loss of self-organizing capability associated with aging or disease is a function of loss of asymmetricity (Costa et al., Phys. Rev. Lett. 95:1–4, 2005). Intuitively, asymmetry refers to the lack of symmetry; in other words, the distribution of signals is imbalanced. This imbalance or dissimilarity can easily be observed in geometry of the phase space plots. Asymmetry is expected to be present in physiological systems (Chialvo and Millonas, Phys. Rev. Lett. 209:26–30, 1995) as it is the fundamental property of a non-equilibrium system (Prigogine and Antoniou, Ann. N. U. Acad. Sci. 879:8–28, 2007). Furthermore, asymmetry is linked with the time irreversibility, which is reported as highest in systems with healthy physiology (Costa et al., Phys. Rev. Lett. 95:1–4, 2005; Costa et al., Phys. Rev. Lett. 89:062102, 2002). Thus, asymmetry represents the presence of complex nonlinear dynamics in physiological signals. So far, very little work has been published in defining and measuring asymmetry in physiological signals (Piskorski and Guzik, Phys. Rev. Lett. 28:287–300, 2007).