A 48-year-old female POD5 from mitral valve replacement presents to hospital with acute shortness of breath and pleuritic chest pain. She also has new right leg swelling.
- What is the unifying diagnosis for this patient’s thrombocytopenia and presentation?
- What clinical probability tool can you use to determine your pre-test probability?
- What drug(s) should be avoided in this patient?
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Diagnosis: classic heparin-induced thrombocytopenia with likely pulmonary embolism and DVT
Q1: What is the unifying diagnosis for this patient’s thrombocytopenia and presentation?
Heparin-induced thrombocytopenia (HIT)
Q2: What clinical probability tool can you use to determine your pre-test probability?
4T score
Q3: What drug(s) should be avoided in this patient?
Heparin products (unfractionated, low-molecular weight), warfarin
Differential Diagnosis for Thrombocytopenia and Thrombosis
• HIT
• Antiphospholipid syndrome
• Malignancy
• DIC
• TTP
• PNH
Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder characterized by thrombocytopenia and thrombosis. It most commonly occurs in patients with recent cardiovascular surgery and those admitted to hospital. HIT is triggered by autoimmune antibodies that target platelets in the presence of heparin. Therefore, any heparin-containing products must be immediately discontinued when HIT is suspected. This includes unfractionated and low-molecular weight heparin, and heparinized access lines.
CBC Pearls
- Review prior CBCs to assess platelet count trend
- HIT should be considered with evidence of new thrombocytopenia and/or thrombosis
- HIT patients should be anticoagulated regardless of thrombosis status
The 4T score uses four clinical parameters (timing of thrombocytopenia, presence of thrombosis, exposure to heparin, and other causes) to calculate the pre-test probability of HIT. Variants of HIT can occur in the absence of heparin but are much less common. All HIT patients should receive anticoagulation regardless of the presence of arterial or venous thromboembolism due to the high risk of thrombosis from platelet activation.
*Warfarin should be avoided in the acute phase of HIT due to the risk of warfarin-associated gangrene and necrosis. However, once the patient’s platelet count has recovered, warfarin can be used for long-term anticoagulation.