1. A method for analyzing at least one cardiac rhythm, wherein the method employs multivariate statistical models that employ entropy measures, wherein the at least one cardiac rhythm comprises an RR-interval series, and wherein the method comprises characterizing RR intervals by at least one dynamic parameter; combining the at least one dynamic parameter with at least one density parameter; classifying the at least one cardiac rhythm based on the combination of the at least one dynamic parameter and the at least one density parameter; and generating a diagnostic output based on the classification.