The parameters of a wavelet shrinkage fltering system for ECG signal treatment are discussed and evaluated. The studied parameters are: wavelet order, number of decomposition levels to evaluate, threshold estimator type, wavelet family type (shift variant or shift invariant), and wavelet family. The study includes a revision of the state of the art and experimental verifcations. A reliable system is defned in this way, and not only based in the morphologic considerations and similarities between the ECG signal and the wavelet function.