The proposed PIVOTAL study will examine a panel of platelet/coagulation activity markers during the perioperative period. The goal is to develop a clinically useful assessment of platelet/coagulation activity for risk stratification that may ultimately serve as a target for therapeutic intervention. This study will enroll 200 patients with peripheral artery disease undergoing vascular surgery. PIVOTAL is funded by American Heart Association and is scheduled to begin enrollment in July 2013 for approximately two years.

To describe platelet activity among PAD subjects undergoing vascular surgery.

To determine whether preoperative platelet activity measurements are independently associated with perioperative cardiovascular events.

To identify demographic, clinical, and surgical factors associated with postoperative platelet activity measurements in patients with established PAD.

Inclusion Criteria:

• Subjects undergoing non emergent vascular surgery
• Use of aspirin within 48 hours prior to surgery
• Age > 21 years of age
• Able and willing to provide written informed consent for the study

Exclusion Criteria:

• Use of any anticoagulant (Coumadin, heparin) within 24 hours to surgery
• Use of any Nonsteroidal Antiinflammatory Drug (NSAID) (such as ibuprofen, naproxen, etc.) within 72 hours
• Thrombocytopenia (platelet count<100) or Thrombocytosis (platelet count>500),
• Anemia (hemoglobin<9),
• Severe kidney disease (CrCl<30ml/min),
• Any known hemorrhagic diathesis.

Study Population will be selected from the inpatient setting at NYU Medical Center and Bellevue Hospital as well as the outpatient setting in the Faculty Group Practice.