This study represents an important step to validate the use of contrast-enhanced ultrasound (CEU) as a clinical research tool that can be used as a biologic readout of new therapies for Peripheral Artery Disease (PAD), and as a clinically-reasonable method for assessing impact of revascularization. The primary aim is to establish that CEU limb perfusion imaging can be used to accurately assess therapeutic improvements in tissue perfusion that are linked to symptom improvement.

The study will be performed in patients with known history of PAD that are scheduled to undergo either surgical or percutaneous revascularization. Limb rest-stress CEU perfusion imaging will be performed before and 3-4 weeks after revascularization. Quantitative measurements of pre-revascularization perfusion, post-revascularization perfusion, and change in perfusion will be compared to symptom status (Rutherford classification and PAD [Criqui] questionnaire) at each study point, and to data on time to onset of claudication on an upright treadmill exercise study (Gardiner protocol). Results of angiography will be scored and allow determination of the relationship between angiographic severity of disease and exercise perfusion.

Inclusion Criteria:

1. History of symptomatic PAD
2. Rutherford score <6
3. Age ≥18 y.o.
4. Scheduled to undergo surgical or percutaneous revascularization

Exclusion Criteria:

1. Major medical illness affecting the limb other than PAD (muscle disease, neuromuscular disease, blood diseases).
2. Pregnant or lactating females (- HCG in women of child bearing age)
3. Hypersensitivity to any ultrasound contrast agent
4. Evidence right-to-left, bi-directional, or transient cardiac shunt; unexplained pulmonary hypertension (PA systolic pressure >40 mm Hg) or more than moderate reduction in left ventricular systolic function identified on screening echo.
5. Allergy to eggs
6. Inability to perform modest plantar flexion exercise

Patients with atherosclerotic peripheral artery disease scheduled to undergo surgical or percutaneous revascularization.