Robert A. M. Gregson, Australian National University, Canberra

Abstract: The internal dynamics of cardiac activity are complex and can vary significantly over time, individuals may exhibit chaos, singularities, and nonstationarity at various time scales. The heart is one of the most studied psychobiological nonlinear systems, at various levels of mathematical and statistical sophistication. Some of its properties can be associated with morbidity or mortality. Prediction of when activity will terminate without acute clinical intervention is only possible at a statistical level over homogeneous groups of subjects under known conditions. Various consequent problems with data analysis at both individual and group levels are reviewed; the two related inferential issues, from individual dynamics to epidemiology, and from epidemiology to individual treatment issues, are critically examined.

Keywords: cardiac dynamics, singularities, system theory, micro and macro levels, epidemiology