Inclusion Criteria

• Male or nonpregnant female greater than or equal to 18 years old
• Ischemic pain originating or persisting at rest, or its clinical equivalent, lasting greater than or equal to 10 minutes and occurring within the 24 hours before enrollment

• At least 2 of the following:

  • ECG changes: New or presumably new ST-segment depression greater than or equal to 0.1 mV (greater than or equal to 1 mm), or transient (<30 minutes) ST-segment elevation greater than or equal to 0.1 mV (greater than or equal to 1 mm) in at least 2 contiguous leads
  • Abnormal cardiac enzymes within the 24 hours before enrollment, defined as elevated troponin I or T greater than the established criteria at each site OR creatine kinase CK-MB level greater than the site's upper limit of normal
  • Age greater than or equal to 60 years

Exclusion Criteria:

• Known or suspected pregnancy
• Increased bleeding risk: ischemic stroke within the last year or any previous hemorrhagic stroke, tumor, or intracranial aneurysm; recent (<1 month) trauma or major surgery (including bypass surgery); active bleeding
• Impaired hemostasis: known International Normalized Ratio (INR) >1.5; past or present bleeding disorder (including congenital bleeding disorders such as von Willebrand's disease or hemophilia, acquired bleeding disorders, and unexplained clinically significant bleeding disorders), thrombocytopenia (platelet count <100,000/mL), or history of thrombocytopenia with GP IIb/IIIa inhibitor therapy, heparin, or enoxaparin
• Angina from a secondary cause such as severe, uncontrolled hypertension (systolic blood pressure >180 mm Hg despite treatment); anemia; valvular disease; congenital heart disease; hypertrophic cardiomyopathy; restrictive or constrictive cardiomyopathy; thyrotoxicosis
• PCI within the past 24 hours, not including coronary angiography only
• Allergy to pork or pork products
• Contraindications to UFH or LMWH
• Recent (<48 hours) or planned spinal/epidural anesthesia or puncture
• Thrombolytic therapy within the preceding 24 hours
• Other serious diseases, including severe liver disease or renal failure [creatinine clearance <30 mL/min
• Treatment with other investigational agents or devices within the previous 30 days, planned use of investigational drugs or devices, or previous enrollment in this trial
• Inability to give informed consent or high likelihood of being unavailable for follow-up
• Not a candidate for intervention, (angiography or PCI)
• Treatment with a direct thrombin inhibitor or a low molecular weight heparin other than enoxaparin in the 7 days preceding enrollment.