Nonlinear dynamics is nowadays widely employed in the study of biological phenomena. In such context, two operational procedures which are not mutually exclusive, but rather complementary, allow us to describe the finality regarding the obtainment of valuable information concerning fibrillation crises. One of the two procedures utilizes elements of nonlinear dynamics (strange attractors, skewness, kurtosis, histograms, Lyapunov exponent etc.) for evaluating atrial fibrillations. The other procedure reconstructs any type of EKG signal, using the mathematical methodology of the Scale Relativity Theory.