If The Person Has An Heart Attack, And Does Not

If the person has an heart attack, and does not respond , what should I do?
I will feel if there is a pulse.
I do not remember the name of the first aid I should give.
My husband is under tremendous stress and had chest pains last night and had trouble sleeping.
If this happens again I will take him to the emergency at the hospital.
Thank you for you attention Willie Lubbers