Filter ECG signal with Wavelet and Python
I will try to answer the question after working on this school project. 

First, why filter an ECG using wavelets? I had a raw signal, full of noise. The filtering of the signal using the wavelet method makes it possible to capture spatial and temporal information very important for an unusual detection.

Here is a tutorial that inspired me, it perfectly describes the role of coefficients:: https://medium.com/@andrewtan_36013/electrocardiograms-qrs-detection-using-wavelet-analysis-a1070505efee