Diagnostic relevance of recurrence plots for the characterization of health, disease or death in humans

Abstract

Introduction: Recurrence plots have been increasingly used to evaluate complex dynamic systems of which the human body is an excellent model. The different quantitative and qualitative elements of recurrence plots in health, disease, and death were analysed. A time series of normal heartbeats were collected in healthy newborns, healthy children, healthy young adults, healthy middle-aged adults, elderly individuals living in nursing homes, individuals with advanced chronic kidney disease, and individuals with declared brain death or in a state of imminent death. Healthy young adults showed the best homeostasis (lower recurrence). Healthy newborns and individuals with declared brain death or in a state of imminent death had higher recurrence values. At the qualitative visual level, healthy young adults showed a more diffuse and uniform distribution, indicative of better homeostasis; for individuals with declared brain death or in a state of imminent death this was totally linear - the worst condition. A parabolic pattern was clearly evidenced. In conclusion, it was possible, using the correlation of only two variables (SDNN and TT), to easily differentiate states of health, disease, and death using recurrence plots.