This study is to assess the function of blood vessels while being treated with different types of blood thinners to determine the effect of these medications on blood vessels.

Inclusion Criteria:

1. Age>18 years old
2. At least two cardiovascular risk factors
3. Demonstrated endothelial dysfunction
4. Evidence of coronary artery disease

Exclusion Criteria:

1. Second (II) or third (III) degree heart block without a pacemaker
2. Known active pathological bleeding, history of stroke, or bleeding diathesis
3. Dyspnea classified as NYHA class III-IV
4. Need for oral anticoagulants
5. Clinically significant valvular heart disease
6. Any concurrent life threatening condition with a life expectancy less than 1 year
7. History or evidence of drug or alcohol abuse within the last 12 months
8. Any surgical or medical condition, which in the opinion of the investigator, may place the patient at higher risk from his/her participation in the study, or is likely to prevent the patient from complying with the requirements of the study or completing the study
9. History of hypersensitivity to any of the study drugs or to medications belonging to the same therapeutic class as the study drugs as well as known or suspected contraindications to the study drugs.
10. Latex allergy
11. History of noncompliance to medical regimens or unwillingness to comply with the study protocol
12. Use of other investigational drugs at the time of enrollment, or within 30 days or 5 half-lives of enrollment, whichever is longer Positive pregnancy test, breast feeding women or women of child bearing potential not using highly effective methods of contraception.
13. Patients who are also taking strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin, nefazodone, ritonavir, and atazanavir)
14. patients taking antiplatelet medications which cannot be stopped
15. severe liver disease