The Influence of the Length of Cardiac Interval Series on Three Different Symbolic Dynamics Approaches

Symbolic dynamics is one of the most relevant heart rate variability approaches to evaluate sympatho-vagal cardiac modulation in health and disease. Distinct symbolization methods have been developed recently to overcome the influence of spurious extreme values, often present in time series of RR intervals. We evaluated the influence of the length of the RR series of rats in basal condition on three distinct symbolization methods, namely sigma, man-mix, and equal probability approaches. Sigma was the only symbolization strategy where the length of the series used did not affect the results. The symbolization results based on the max-min and equal probability approaches returned different results according to the size of the series used. Moreover, results also showed differences in the distribution percentage of symbolic indices according to the symbolization approach applied.