Testing the cardiac rhythm for chaoticity

Processes dominated by low-dimensional deterministic chaos are known to produce finite numerical estimates of the correlation dimension. This property has been often reversed in studying systems of unknown dynamics, with the risk of misleading results; in fact, stochastic processes with power law spectra produce a finite correlation dimension. We implemented a pictorial test proposed in literature to enhance the dynamical correlation for each of three biological series: ECG samples, HR and RR trends. A comparison was performed against simulated periodic, chaotic and stochastic processes. The results available so far indicated a strong dynamical correlation over the ECG, whereas the presence of any correlation was completely masked by a noise like structure on both HR and RR series, suggesting that caution is required in interpreting the meaning of correlation dimension for real processes