Heparin-Induced Thrombocytosis with Thrombosis (HIT)
Heparin-associated thrombocytopenia (HAT)
Alternate names:
Heparin-induced thrombocytopenia type II
Cause:
1 – 5% of patients on therapeutic heparin for >5 days develop IgG antibodies to:
Heparin-PF4 complexes
The IgG-heparin-PF4 immune complexes then bind to Fc receptors on platelets resulting in:
Activation of platelets
Thrombocytopenia
Microvascular thrombosis
Type of heparin most likely to induce HIT:
Bovine-derived heparin
Porcine-derived heparin can also induce it