Cardiovascular disease is a major health problem across the world. The age-adjusted death rate for cardiovascular disease has significantly decreased during recent decades, and this decline is related to the widespread use of evidence-based medicines. However, even upon optimal medical therapies, patients remains at a substantial residual risk for acute coronary syndrome (ACS) or acute ischemic stroke(AIS), requiring new therapeutic approaches. Plaque rupture and subsequent thrombus formation is the most common cause of ACS and AIS. Atherosclerosis is a chronic immune-inflammatory disorder. Inflammation is believed to be critically important to plaque rupture by destroying the fibrous cap, thereby predisposing to ACS and AIS. Cross-talk between coagulation and inflammatory pathway via protease-activated receptor (PAR) activation has been recognized . Factor Xa is responsible for promoting inflammation, which participate in the atherosclerotic process and plaque destabilization either directly via activation of PARs or indirectly through the generation of thrombin .~In the Cardiovascular Outcomes for People Using Anticoagulation Strategies (COMPASS) trial, the rate of a composite of cardiovascular death, stroke, or myocardial infarction was lower by 24% with low-dose rivaroxaban (2.5 mg twice daily) plus aspirin than with aspirin alone among patients with stable atherosclerotic vascular disease, but the rate of major bleeding was higher by 70%. Interestingly, the rate of stroke was remarkably lower by 42% with rivaroxaban plus aspirin than with aspirin alone. The substantial net clinical benefits seen with rivaroxaban plus aspirin may not be fully explained by their anti-thrombotic effect alone, suggesting pleiotropic effects coupled with factor Xa antagonism. Besides its role in hemostasis and thrombosis, low-dose rivaroxaban may inhibit atherosclerotic plaque inflammation and decrease plaque destabilization. To test this hypothesis, the investigators will compare the effects of aspirin versus aspirin plus low-dose rivaroxaban on carotid atherosclerotic plaque inflammation using serial 18F-fluorodeoxyglucose (FDG) Positron Emission Tomography/Computed Tomography(PET-CT) imaging of carotid artery and ascending aorta.
Primary Study Objective : To compare the effects of low-dose rivaroxaban plus aspirin versus aspirin on atherosclerotic plaque inflammation using serial FDG Positron Emission Tomography/Computed Tomography(PET-CT) imaging of carotid artery and ascending aorta.~Secondary Study Objective : To compare the effects of low-dose rivaroxaban plus aspirin versus aspirin on biomarkers including high-sensitivity C-Reactive Protein(CRP) and lipid profiles.