The purpose of this research is to study why some people do not respond to the benefits of aspirin therapy. The benefit of aspirin is cardioprotection, or decreasing the risk of heart attack and/or stroke. Aspirin works by disabling the platelets, part of the blood cells used in clotting, from sticking together and forming blood clots, thus protecting the heart. It has been observed that failure to respond to aspirin therapy occurs in about 10% of the general population and that despite taking aspirin everyday, this group of non- responders is not getting protection for their heart. The investigators would like to determine why and how this happens.