A Comparative Sudy Comparing Argatroban® IV vs Desirudin SC for Suspected HIT With or Without Thrombosis Syndrome

1. Provide written Informed Consent
2. Be at least 18 years of age.

3. A suspicion of heparin-induced thrombocytopenia with or without thrombosis syndrome (HIT/TS) due to one of the following clinical scenarios:

   1. Patients who are receiving heparin/LMWH or have received heparin/LMWH within the previous 100 days AND one of the following:

      • have a fall in platelet count of > 30% from a baseline prior to heparin/LMWH, OR
      • have a thrombotic event, OR
      • develop skin lesions secondary to subcutaneous heparin (even if the patient is no longer receiving heparin therapy when thrombocytopenia, thrombosis or skin lesions occur).

      Patients with thrombosis or skin lesions need not have concomitant thrombocytopenia to be included.

   2. A rapid fall in the platelet count by >30% from baseline within 24 hours after starting heparin/LMWH in patients with suspected exposure to heparin or LMWH in the previous 100 days (e.g. hospitalization or invasive procedure within the past 100 days).
   3. In post-operative cardiac surgery patients, development of thrombocytopenia defined as a decrease in platelet count by >30% from the post-operative peak; or patients whose platelet count fails to increase post-operatively (e.g. remains \< 100,000 mm3 at Day 4 or later, calendar day of surgery=Day 0).
4. In patients with the diagnosis of HIT/TS established by a hematology consultant, but in whom the above criteria are not fulfilled, the Investigator should contact the Medical Monitor for consideration of the patient's inclusion in this study (A hematology consult is highly advisable, but not required prior to randomization).

Exclusion Criteria:

• Confirmed pregnancy (if woman of child-bearing potential- urine or serum pregnancy test).
• Patients with suspected or confirmed pulmonary embolism, requiring continued anticoagulation or acute ischemic stroke will be excluded
• Cerebrovascular accident within the previous 6 months
• Intracranial neoplasm, arteriovenous malformation or aneurysm.
• Severe renal insufficiency as determined by measured or estimated creatinine clearance \< 30 ml/min.
• Known allergy to Argatroban®, Desirudin or hirudin derived drugs, or known sensitivity to any component of the product
• Patients receiving recombinant hirudin (e.g. lepirudin) within the previous 6 months prior to enrollment.
• Patients receiving >2 doses of fondaparinux for treatment of suspected HIT
• Multi-system organ failure or estimated survival of less than 30 days.
• Participation in other clinical research studies involving the evaluation of other investigational drugs or devices within 30 days of enrollment
• Refusal to undergo blood transfusion should it become necessary
• Active bleeding or irreversible coagulation abnormality
• Uncontrolled hypertension defined as a blood pressure >180/110 mm Hg.
• Patients requiring indwelling mechanical intervention such as left-ventricular assist device, intra-aortic balloon pump, veno-venous ultra filtration, etc.
• Severe liver disease and any other disease or condition, which, in the judgment of the Investigator, would place a patient at undue risk by being enrolled in the trial, or cause inability to comply with the trial.