Fixed structure Mathematical Morphology (MM) operators have been used to detect QRS complexes in the ECG. These schemes are limited by the arbitrary setting of threshold values. Our study aims at extracting QRS complex fiducial points using MM with an adaptive structuring element, on a beat-to-beat basis. The structuring element is updated based on the characteristics of the previously detected QRS complexes. The MIT-BIH arrhythmia and Physionet QT databases were respectively used for assessing the performance of R-waves and other fiducial points detection. Results show comparable or better performance than the state-of-the-art and an efficient extraction of Qand S-waves as well as onset and offset points of the QRS complex