Скачать или смотреть Heparin Induced Thrombocytopenja (HIT)

Heparin Induced Thrombocytopenia

The pathophysiology of involves an immune response triggered by the interaction between heparin and platelet factor 4 (PF4), a protein released from platelets upon activation. In most cases, heparin binds to PF4, forming complexes that are recognized by the immune system as foreign. This prompts the production of antibodies, specifically IgG antibodies, against the heparin-PF4 complex.

These antibodies can attach to the surface of platelets when the heparin-PF4 complex is present. This leads to platelet activation and aggregation, which can paradoxically result in a hypercoagulable state, increasing the risk of thrombosis.


The 4T score is a clinical scoring system used to assess the likelihood of Heparin-induced thrombocytopenia (HIT) based on four clinical parameters. It helps healthcare professionals evaluate the probability of HIT in a patient who is suspected of having this condition. The four parameters considered in the 4T score are:

1. Thrombocytopenia: The degree of reduction in platelet count.
2. Timing of platelet count fall: How soon after heparin exposure the platelet count decreased.
3. Thrombosis or other sequelae: The presence of new thrombosis or other complications.
4. Alternative causes of thrombocytopenia: The likelihood of other reasons for the reduced platelet count.

Each parameter is assigned a score, and the cumulative score can help classify the probability of HIT into low, intermediate, or high. The 4T score assists clinicians in making informed decisions about managing patients suspected of having HIT, such as determining whether to continue heparin therapy or to switch to an alternative anticoagulant.