Please refer to the detailed answer below
After going through the medical details provided by you of your mother I understand your concern and I would like to tell you that the Ecg is showing ST T changes in infero lateral leads which can be due to some myocardial ischemia
should be done for evaluating resting heart function and in my view it will probably come normal. So the next step is to undertake a Stress test
in the form of TMT or a stress echocardiography.
These things needs to be evaluated as if they left unattended they might create problems later on.
I hope this information will be helpful and will guide you properly.
Dr Bhanu partap