What are the medical and nursing management in myocardial infarction?

You don't really specify at what point of time in the MI. A person who is having an MI or myocardial infarction will need rapid intervention in order to preserve as much heart muscle as possible. The MI is caused by a blocked coronary artery(ies) that supplies the heart with it's blood, causing mild to severe chest pain. radiating into one or both arms and into the jaws. nausea and vomiting can occur with heavy sweating. Or there may be zero pain, but a feeling of "impending doom"
When a person presents to the ER with these symptoms, many things should happen. The person has an extensive history of when all of these events started, how bad the pain is etc. A cardiac monitor is placed on the patient, an IV is started with blood drawn for Lab tests and oxygen is started. The patient will get an EKG which basically is a map of the heart's electrical system. The doctor is looking for abnormalities in the different areas of the heart. The Lab will test for a complete blood count, electrolytes and specifically for changes in the cardiac enzymes and troponin levels( an enzyme specific to cardiac muscle that is released when the muscle is damaged.) The patient should receive pain medicine, usually morphine, which also acts as an anti-anxiety medicine. When the doctor looks at the EKG and finds an area of the heart that shows electrical blockage, a consult with a cardiologist and transfer of the patient to a "cath lab" where the patient undergoes a procedure known as angioplasty. The cardiologist may inset a "stent", a wire support that keeps the artery open after the blockage is removed. It is very important to know that the doctors and nurses work as a team to get this patient the care he or she needs. The worse case scenario is the patient waits to seek medical attention when these symptoms begin and the damage to the heart muscle is so severe that the heart will not recover. The patient can have so much electrical problems, the heart stops and unless CPR is started within 4 minutes, the patient will die.

LEG did a good job explaining but forgot the most important and easiest thing that anyone can do even without medical training which is to chew an aspirin. This is the first medical intervention that should be taken. After that other medications can be used to slow down the heart rate or lower/raise blood pressure if necessary. Morphine may be given for pain.
Then EKG and cardiac enzymes (troponins) and if criteria is met, cardiac catheterization.