Multiple Daily Doses of Aspirin to Overcome Hyporesponsiveness Post Cardiac Bypass Surgery (ASACABG)- Part B

Cardiac bypass surgery is an important treatment for patients with severely blocked arteries (tubes that delivery oxygen and nutrients to the heart). Hundreds of thousands of these operations are done each year to help relieve patients' chest pain and to prevent future heart attacks. The surgery is done by "bypassing" blood flow around badly clogged arteries by sewing on healthy vessels from another part of the body (usually from the leg or the chest). Aspirin (a blood thinner) is given to patients once a day after their surgery because it stops "sticky" cells in the blood (platelets) from blocking these new vessels (which may lead to a future heart attack). Research has shown that aspirin does not work as well in people after they have bypass surgery as the investigators might expect (for reasons that are not fully understood). One reason aspirin may not work as well after surgery is because the body makes many more platelets after surgery than it would under normal circumstances. All of these new platelets overwhelm the aspirin and continue to be "sticky" and ready to block off arteries. The investigators believe that giving multiple daily doses of aspirin following bypass surgery is more effective at blocking platelet activity than giving aspirin once daily.