Your question is too broad, could you narrow it a bit? :-) on the other hand, when it is intentional, you are getting the following broad answer.
I will bring to your attention a very interesting research field dealing with ECG, EEG, and many other bio-signals, which is based on complex systems.
Complex systems are the most advanced type of mathematics employed in the edge of the contemporary biomedical research. They appear to have the richest expressive vocabulary enabling to model many biological phenomena that resisted the description by all other mathematical methods, theories, and approaches.
In general, all complex systems are so complicated that we lack a theory describing their behavior. There is one way how to overcome this deficiency: complex systems measures based on the notion of entropy. In our case, it is the information entropy.
The formation entropy enables to grasp and numerically asses the actual state of any given complex system and its changes with time.
That is a great help because we are getting in our hands a tool that enables us to quantify many, so far unreachable, information hidden within complex systems.
This new area of research is not easy to grasp for non-specialists. Nevertheless, it is a good idea to try to understand at least the basics of it because those approaches are the future in biomedicine. They enable to develop personalized, predictive medicine in the future.
Take a look into "The Illustrated wavelet Tranform Handbook".. There are some examples of application of the wavelet transform to analysis in medicine.. so YES..
also you can have a look into "https://physionet.org/"