Quick Answer:
Call 911 or the appropriate local emergency number.
Don't dismiss the signs of a heart attack. If you are unable to summon an ambulance or emergency vehicle, have a neighbor or a friend drive you to the nearest hospital. Only drive yourself if you have no other choice. Driving yourself puts you and others in danger because your condition can worsen.
While waiting for emergency assistance, make them chew and swallow an aspirin.
Aspirin prevents your blood from clotting. It may reduce heart damage if taken during a heart attack. If you are allergic to aspirin or have been advised by your doctor not to take it, do not take it.
If nitroglycerin is prescribed, give it to them.
If you believe they are having a heart attack and your doctor has previously prescribed nitroglycerin for you, take it as directed while you wait for emergency medical assistance.
If the person is unconscious, begin CPR.
If the person isn't breathing or there isn't a pulse, start CPR to keep the blood flowing after calling for emergency medical help.
Push hard and fast on the person's chest in a fairly rapid rhythm — about 100 to 120 compressions per minute.
If an automated external defibrillator (AED) is immediately available and the person is unconscious, use it according to the device's instructions.