Clinical Utility of Endothelial Dysfunction in PAD

Inclusion Criteria:

1. Male and female subjects age 21-99 years old.
2. Peripheral Arterial Disease. PAD is defined clinically and by angiography, magnetic resonance imaging, vascular ultrasound, or ankle brachial index less than 0.9.
3. Able to provide informed consent and complete the study procedure.
4. Patients undergoing non-emergent vascular surgery (peripheral arterial bypass, abdominal aortic aneurysm repair, carotid endarterectomy, or limb amputation) or other non-cardiac surgery.

Exclusion Criteria:

1. Emergent or urgent surgery that must be performed sooner than one week after enrollment
2. Unstable angina, myocardial infarction, stroke, coronary revascularization, or decompensated heart failure within 1 month of enrollment. Patients who require cardiac catheterization and surgical or percutaneous coronary revascularization prior to vascular surgery will be excluded.
3. Clinically evident major illness of other organ systems, including cancer, end-stage renal disease, hepatic failure, or other conditions that make participation inappropriate.
4. Women who are lactating, pregnant, or of childbearing potential and not using a reliable contraceptive method. Pregnancy will be excluded by a urine pregnancy test.
5. Patients with liver function tests or serum creatine kinase >3 times the upper limit of normal.
6. Patients who have received an investigational drug within 30 days of enrollment.
7. Patients or subjects with a history of a psychological illness or condition such as to interfere with the subject's ability to understand the requirements of the study.
8. Known occlusive atherosclerosis of the subclavian artery or upper extremity, because such disease will interfere with induction of reactive hyperemia during the brachial artery ultrasound studies.
9. Patients will be excluded if they are taking vitamin C in a dose greater than 2 times the Recommended Daily Allowance (>120 mg/day) within 1 month of enrollment.