Carry a few Aspirin 81mg in your pocket just in case. If things don't feel right, chew them and call 911. Worst case it will be a false alarm and you may get a bit of stomach irritation.
This saved my friend's live. Popped the "baby aspirin" (as he calls it) and drove himself to the hopsital. The doc confirmed he had 95%-ish blockage and would have died if not for the Aspirin.