Participants will be examined daily and evaluated for bleeding. Blood samples (30 ml of blood) will also be drawn before or after aspirin is given and 24 hours, 72 hours and 7 days after aspirin treatment to study platelet function. Participants will be followed up on the study for 7 days. Participants will be followed up in the cardiology clinic within 1-2 weeks after discharge from the hospital, then once a month for six month. Further follow up will be every 6 month. Patients are requested to follow up with cardiology by phone at any time for any bleeding.