Heparin-associated thrombocytopenia: an update

Area of Science:

• Pharmacology
• Immunology
• Hematology

Background:

• Heparin use can cause thrombocytopenia (HAT), with type I being transient and type II posing significant thrombotic risks.
• HAT type II, though often underestimated, can lead to severe arterial or venous thromboses and bleeding, frequently linked to unfractionated heparin (UH) but also low molecular weight heparins (LMWH).

Purpose of the Study:

• To review the pathophysiology, diagnosis, prevention, and management of heparin-induced thrombocytopenia type II (HAT-II).
• To highlight the underestimation of HAT-II's clinical significance and incidence by some clinicians.

Main Methods:

• Literature review of studies on heparin-induced thrombocytopenia.
• Analysis of pathophysiology involving immune complexes (Platelet Factor 4-heparin antigen, Fc gamma RII receptors).
• Evaluation of diagnostic tests, preventive strategies, and therapeutic options for HAT-II.

Main Results:

• HAT-II involves immune complexes activating platelets and endothelial cells, leading to thrombosis.
• Estimating HAT-II incidence is challenging, but thrombotic events, especially venous, may be more frequent than previously thought.
• Current diagnostic tests are not ideal; prevention includes LMWH preference, early oral anticoagulation, and platelet monitoring.

Conclusions:

• Immediate heparin discontinuation and avoidance of platelet transfusions are key in HAT-II therapy.
• Alternative anticoagulants like Org 10172 or Ancrod are recommended, with potential roles for hirudin, prostacyclin analogues, and other agents in specific cases.
• Managing previously sensitized patients requiring heparin necessitates careful consideration of alternative treatments.