Left Ventricular Assist Device (LVAD) Specialized Centers of Clinically Orientated Research (SCCOR) Coagulation - Acute Intrinsic Pathway Antagonist (IPA)

Inclusion Criteria: * Signed informed consent, release of medical information, and HIPAA forms * Age greater than or equal to 18 years * Male, postmenopausal female, or female who may become pregnant but is using adequate contraceptive precautions (defined as oral contraceptive, intrauterine devices, surgical contraception or a combination of a condom and a spermicide), with negative pregnancy test * Implanted with an FDA-approved LVAD (for BTT or DT indication, e.g. HeartMate® XVE) within 72 hours prior to randomization, and able to receive the first dose of study drug by 72 hours (+6 hours) post LVAD implantation * Post-op hemostasis adequate for starting low level anticoagulation (as assessed by surgeon) * Extubated and able to take oral medication Exclusion Criteria: * Evidence of active bleeding within 24 hours prior to randomization * History of a platelet disorder, including but not limited to thrombocytopenia and thrombasthenia * Thrombocytopenia with platelets \<80,000/ml within 48 hours prior to randomization * History of an inherited or acquired coagulation disorder * Hemoglobin \<8 g/dL (4.85 mmol/L) or hematocrit \<26% within 24 hours prior to randomization * Clinical indication for (or the intention to use) standard anticoagulation therapy at time of randomization (e.g., atrial fibrillation or DVT) * Intention to treat with more than 325 mg aspirin daily * Any clinical requirement or intention to treat with phenytoin, tolbutamide or warfarin post randomizatio…