What is the risk of Deep Vein Thrombosis (DVT) in someone with Heparin-Induced Thrombocytopenia (HIT)?

From the Guidelines

For a patient with deep vein thrombosis (DVT) who also has heparin-induced thrombocytopenia (HIT), non-heparin anticoagulants must be used, as recommended by the most recent guidelines 1. The recommended treatment options include direct thrombin inhibitors such as argatroban (initial dose 2 mcg/kg/min as continuous IV infusion, adjusted based on aPTT) or bivalirudin (0.15-0.2 mg/kg/hr), or factor Xa inhibitors like fondaparinux (7.5 mg subcutaneously once daily for patients 50-100 kg, with dose adjustments for weight variations) 1. For long-term management, transition to oral direct oral anticoagulants (DOACs) such as rivaroxaban (15 mg twice daily for 21 days, then 20 mg daily) or apixaban (10 mg twice daily for 7 days, then 5 mg twice daily) is appropriate 1. Warfarin can also be used but should be started only after platelet recovery and with overlap with a non-heparin parenteral anticoagulant 1. Some key points to consider in the management of HIT include:

• The primary prevention of HIT is mainly ensured by prescribing heparins only in validated indications, preferably prescribing oral anticoagulants or LMWH, and limiting the duration of heparin treatment to the shortest possible time 1.
• The secondary prevention of HIT is based on establishing a medical certificate or card attesting to the reality of this history, performing a sensitive biological test to test the absence or persistence of PF4-specific antibodies, and preferably prescribing an oral anticoagulant or fondaparinux in case of a history of HIT 1. It's crucial to avoid all forms of heparin including low molecular weight heparins and heparin flushes as they can worsen HIT, which is an immune-mediated reaction where antibodies form against platelet factor 4-heparin complexes, causing platelet activation, thrombocytopenia, and paradoxical thrombosis 1. Treatment duration is typically 3-6 months depending on whether the DVT was provoked or unprovoked 1. The diagnosis of acute HIT is difficult and must integrate clinical circumstances and associated treatments, with biological confirmation of the diagnosis being necessary in all cases 1.

From the Research

Diagnosis of DVT in someone with HIT

• The diagnosis of HIT can be established using an HIT antibody test 2
• The "4 Ts" can be used to support a clinical diagnosis of HIT: thrombocytopenia, timing of platelet count fall, thrombosis or other complications, and other causes for thrombocytopenia 2, 3
• The gold standard in diagnosing HIT is the 14C-serotonin release assay (14C-SRA) assay, which has high sensitivity and specificity 2

Treatment of DVT in someone with HIT

• Anticoagulation in HIT patients is essential due to the increased risk of thrombosis 2
• Treatment consists of utilizing alternative, nonheparin anticoagulants like lepirudin, argatroban, bivalirudin, or fondaparinux 2, 4, 3
• Direct thrombin inhibitors (DTI's) such as lepirudin and argatroban are effective in treatment of heparin-induced thrombocytopenia resulting in rapid normalization of platelet counts and a reduction in thrombotic events 5
• The use of DOACs in acute HIT should be reserved for clinically stable patients without severe thrombotic complications 4

Management of DVT in someone with HIT

• Early diagnosis based on a comprehensive interpretation of clinical and laboratory information improves clinical outcomes 6
• Clinical management of patients with HIT is with a non-heparin anticoagulant such as a direct thrombin inhibitor or danaparoid followed by a vitamin K antagonist for long-term treatment 6
• Important drug-specific limitations, dosing, and monitoring guidelines must be respected for patient safety 6