  The complexity of a signal can be measured by the Recurrence period density
entropy (RPDE) from the reconstructed phase space. We have chosen a window
based RPDE method for the classification of signals, as RPDE is an average
entropic measure of the whole phase space. We have observed the changes in the
complexity in cardiac signals of normal healthy person (NHP) and congestive
heart failure patients (CHFP). The results show that the cardiac dynamics of a
healthy subject is more complex and random compare to the same for a heart
failure patient, whose dynamics is more deterministic. We have constructed a
general threshold to distinguish the border line between a healthy and a
congestive heart failure dynamics. The results may be useful for wide range for
physiological and biomedical analysis.
