Registered Cardiovascular Invasive Specialist (RCIS) Practice Test

In the context of coagulation, what role does antithrombin play?

1. It promotes clot formation

2. It inhibits clotting factors

3. It activates coagulation pathways

4. It stabilizes fibrin

The correct answer is: It inhibits clotting factors

Antithrombin plays a crucial role in the regulation of coagulation by inhibiting various clotting factors in the blood. This protein primarily targets serine proteases, which include factors IIa (thrombin), IXa, Xa, XIa, and XIIa, effectively slowing down the coagulation cascade. By neutralizing these factors, antithrombin prevents excessive clot formation and maintains a balanced hemostatic process. The inhibition of clotting factors is essential for controlling the size and formation of blood clots, ensuring that they form only when necessary, such as in response to vascular injury, and preventing unwanted thrombus development that could lead to conditions like thrombosis. In contrast, options that suggest promoting clot formation, activating coagulation pathways, or stabilizing fibrin do not align with the function of antithrombin, which is primarily protective in nature, ensuring that clotting does not occur excessively or inappropriately.