Your father may have had what is referred to medically as an ischemic (lack of blood flow due to vessel blockage) heart attack. You don't state what test was given to conclude there is heart muscle damage. If there has been a significant heart attack, your father would have symptoms of shortness of breath, possible chest pain, fatigue, etc.
Assuming there has been a heart attack, the best procedure would be to have an echocardiogram and that exam would determine if the heart wall has damaged heart cells from the heart attack. If the heart attack was significant, the heart wall would not be able contract effectively, and the heart would have a decrease of blood put into circulation. An echo is able to calculate the amount of blood pumped with each heartbeat.
If your father does not have any symptoms, and the echo shows very little damage, if any, There may not be any further need for futher testing. If your father is having symptoms of chest pain, shortness of breath, etc. and medication does not provide relief then an angioplasty may be necessary to open any blocked vessels that are causing pain, etc.
Thanks for sharing, and if you have any followup questions or comments, you are welcome to reply. Take care and I wish your father well going forward..