Renormalised entropy: a new method of non-linear dynamics for the analysis of heart rate variability

Because classical parameters of heart rate variability analysis describe only linear or periodical behaviour, more complex relations cannot be recognised. Since the heart is a very complex system it is useful to have a criterion of relative degree of order which measures the complexity of patient´s heart rate. Klimontovich´s S-theorem offers an approach to compare two different states of energy. According to the assumption that the mean effective energy of these two states has to be equal the spectral distribution of the reference person is renormalised to an equal energy state. The last step of the procedure is the calculation of the difference of Shannon entropies of both frequency distributions. The obtained results suggest that renormalised entropy is a suitable method for the detection of patients with high risk for sudden cardiac death. First findings of a current simulation study show the special capability of renormalised entropy as a measure of non-linear behaviour