QRS activity duration may be indicative of cardiac tissue health. Accordingly, maps of QRS activity duration may be beneficial to practitioners. To this end, an electroanatomical mapping system can receive an electrogram signal and analyze it by transforming it into the wavelet domain, computing an energy function of the resultant scalogram, and computing QRS activity duration using the energy function. A graphical representation of the QRS activity duration can be output, for example on a three-dimensional cardiac model. Areas of diseased substrate can be identified on the output； in some aspects of the disclosure, diseased substrate corresponds to areas where the QRS activity duration exceeds a preset threshold, such as about 70 ms.
