Aspirin for Heart Attack and Unstable Angina https://www.healthlinkbc.ca › medications
After you call 911 or other emergency services, the operator may tell you to chew 1 adult-strength or 2 to 4 low-dose aspirin. Or you might be given aspirin in the ambulance or emergency room. Aspirin slows blood clotting. So a blood clot that is causing the heart attack stays smaller.