The Epidemiology of Bleeding and Clotting in Patients Undergoing Heart Transplantation, Coronary Artery Bypass Graft Surgery,or Implantation of Left Ventricular Assist Devices

The purpose of this study is to obtain data or information on how blood clotting factors are activated during open heart surgery. In particular, the investigators are interested in how blood clotting factors are activated by the heart-lung bypass machine and by left ventricular assist devices (LVAD). Patients on these two machines have an increased risk of bleeding and blood clot formation. This is because both machines stimulate the intrinsic coagulation pathway, one of the chemical pathways that cause blood to clot. The process of surgery itself also stimulates the "extrinsic coagulation pathway," the other chemical pathway that causes blood to clot. Stimulating these coagulation pathways can use up the body's clotting factors. As a result, patients may be at risk for both bleeding and blood clot formation. The investigators would like to study how the blood factors are activated during and after surgery, to help develop treatments to prevent bleeding and clot formation.