Find best time period to do cardiovascular imaging using machine learning.

I have ECG data from a large number of people, ECG signal consists of QRS wave(Heart Pumping), in this time heart is pumping so imaging cannot be done, but after the QRS wave has passed during R-R interval imaging can be done because heart is relaxed now. This case is good for normal people but in case of patients there are still abnormalities after QRS wave so i want to use machine learning to train the system to find the best time span to imaging in any case either it is patient or it is a normal person. So kindly guide how to do that ?

[Anton Semechko]

My suggestion to you is to search "ECG classification" on Google Scholar