The words 'heart attack' are far from meaningless. They replace myocardial infarction which means that the tissue has no blood supply in a specific area. Some patients develop collaterals to counteract the problem, some manage to dissolve or dislodge a blockage in time, while others may be treated quickly enough to stop permanent damage. There are of course just as many unfortunate people who do not live or recover. If a cardiologist uses the words heart attack then this means something specific.
My entire family has been visiting Rabindranath Tagore International Institute of Cardiac Sciences for any cardio related health issues and even for general heart check ups. I recently accompanied my grandfather for an OPD session and I am impressed by the way Dr. Binayak Deb treats every patient personally with utmost interest and his nurses and staff are always in the cabin to provide all kinds of help. Hats off to Dr. Binayak Deb and team.
Cardiac rehab is recommended. He is probably not allowed to exercise freely in the first few weeks because damaged heart tissue (if there is any) might tear. During that time it is good to exercise under guidance of a rehab nurse.
After that period scar tissue (if there is any) is formed and it should be safe to exercise.
(Cardio) exercise and a healthy lifestyle are best to recover fast.
Try to get him into a cardiac rehabilitation program.
For starters, the word "heart attack" is completely meaningless.
It is often applied when someone has simple pain from lack of oxygen and tisue ischemia called "angina". People with angina may or may not have any actual damage to the heart. They do have a narrowing of the interior of the blood vessels supplying the heart.
If there is "death" of tissue or necrosis, there may be a little damage or a lot of damage. Depending on where the damage is will determine the severity of the problem. The most problems coime from damage that interferes with the transmittion of electrical signals from the atria.
I have no idea what "heavy condition means".
In general, every case is different. Get a medical release to speak with your father's cardiologist for specific recommendations. Mild exercise, good diet, control of blood pressure, and taking medications as prescribed represent the basic plan.
This all depends on if there was any damage to the heart, and if so, how much. Recovery is as much mental as physical. Most people feel very vulnerable after a heart attack and find it hard to return to normal life. How is he emotionally?