Pathophysiology

There are two types of HIT, depending on the absence or presence of an immune mediation. Type 1 is a non-immune-mediated direct activation of platelets by heparin that occurs within 48–72 h, usually resolves after heparin withdrawal and does not typically complicate anticoagulation for CPB. In contrast, Type 2 is immune-mediated and relies on the activation of the heparin/platelet factor 4 (PF4) antigen complex, typically 5–14 days after heparin exposure. This complex binds immunoglobulin IgG