Unless you are an M.D. you SHOULD NOT give asprin to a suspected heart attack victim.
Get them to lie down. Elevate their limbs. Keep them calm. Call 911.
The reason thay you DO NOT give it is that it is very difficult for untrained individuals to differentiate between a heart attack victim and someone who is suffering a stroke.
If it is a stroke you will kill them.
A stroke is basically the same thing as a heart-attack, just in different places. Giving aspirin to someone with a stroke won'kill him. Maybe you mean a aneurysm or internal bleeding?
I personally carry Acethaminophen, Ibuprofen and Asperin. This gives you some options in case someone is allergic, has GI-complains, etc.