Fail. You shouldn't give anyone pills if they're having a heart attack, unless it's prescription medication they've been told to take. He may well be allergic to them for all you know.
Okies, you can just wait for the paramedics to turn up and offer it then. Of course you would check if they are allergic, more that likely they will know, especially if they are in an at risk group (Hx of a TIA, so could already be prescribed a 75mg daily dose). Even if they are allergic to NSAIDs, then that handy drug clopidogrel (which some ambulances now carry) could be your best bet. But of course, you already knew that...