There is a difference between having a heart attack and having a cardiac arrest. Someone having a heart attack who is alert, has a pulse and is breathing on their own does not need CPR. They do need medical treatment and should call 911 immediately. If someone is not responding, does not have a pulse and is not breathing this is called a cardiac arrest. A person in this situation would need 911 called, CPR begun and would need to be defibrillated as quickly as possible.
A Answers (2)
First, if you believe someone is having a heart attack, then call 911 ASAP and get help. Let me clarify something before answering your question. Just because you believe that someone is having a heart attack, it does not mean that they need CPR.
CPR is only needed when someone is not breathing and/or their heart has stopped beating. You should first make sure they have not simply fallen or have some other problem by trying to vigorously rouse them or by rubbing hard on their chest with your knuckles. If no response, call 911 and then begin CPR.
I would suggest going to the American Heart Association or American Red Cross site for more information about how to perform CPR most effectively.