Heparin resistance is likely in patients with which hereditary deficiency?

Heparin resistance is likely in patients with which hereditary deficiency?

• A. Factor V Leiden mutation
• B. Protein C deficiency
• C. Protein S deficiency
• D. Antithrombin or antithrombin III deficiency

Answer: (D)

Heparin works mainly by binding to and accelerating the action of antithrombin III to inhibit thrombin and factor Xa. If a patient has hereditary antithrombin deficiency, there is not enough functional antithrombin available for heparin to potentiate, so the expected anticoagulant response is blunted. This is why heparin resistance occurs in those with antithrombin deficiency, which can be quantitative (low levels) or qualitative (dysfunctional). The other hereditary thrombophilias—such as factor V Leiden, protein C deficiency, or protein S deficiency—alter procoagulant or anticoagulant pathways but do not reduce the ability of antithrombin to be activated by heparin, so they don’t cause the same resistance. In practice, patients with hereditary antithrombin deficiency may require ATIII replacement or alternative anticoagulation to achieve the desired effect.

Heparin works mainly by binding to and accelerating the action of antithrombin III to inhibit thrombin and factor Xa. If a patient has hereditary antithrombin deficiency, there is not enough functional antithrombin available for heparin to potentiate, so the expected anticoagulant response is blunted. This is why heparin resistance occurs in those with antithrombin deficiency, which can be quantitative (low levels) or qualitative (dysfunctional). The other hereditary thrombophilias—such as factor V Leiden, protein C deficiency, or protein S deficiency—alter procoagulant or anticoagulant pathways but do not reduce the ability of antithrombin to be activated by heparin, so they don’t cause the same resistance. In practice, patients with hereditary antithrombin deficiency may require ATIII replacement or alternative anticoagulation to achieve the desired effect.