Part A: This part includes a 12-day Initial PK, PD, and Safety Assessment Period. Participants in Part A will not participate in Part B. Randomization in Part B of this study will begin once the cumulative data from the Initial PK, PD, and Safety Assessment Period in Part A are deemed acceptable by the Independent Data Monitoring Committee. Part A of the study will consist of an up to 21-day Screening Period, a 12-day Initial PK, PD, and Safety Assessment Period, a 12-month Open-Label Treatment Period, and a 30-day Follow-Up phone contact. Part B: Participants will be randomly assigned to two treatment groups and randomization ratio will be 2:1 for rivaroxaban and ASA. ASA will be used as control. There will be an up to a 21-day Screening Period, a 12 month Open-Label Treatment Period and a 30-day Follow-Up phone contact.
