Factor VIIa-Antithrombin complexes during cardiac surgery using cardiopulmonary bypass.

Area of Science:

• Biochemistry
• Cardiovascular Surgery
• Hemostasis and Thrombosis

Background:

• Antithrombin is a key inhibitor of coagulation Factor VIIa (VIIa), particularly when VIIa is bound to tissue factor and in the presence of heparin.
• Factor VIIa levels increase in the surgical field during cardiopulmonary bypass but decrease in patient circulation, suggesting in vivo inhibition.
• The physiological role of antithrombin in inhibiting VIIa during cardiac surgery remains to be fully elucidated.

Purpose of the Study:

• To investigate the role of antithrombin in the inhibition of Factor VIIa during cardiopulmonary bypass surgery.
• To quantify VIIa-antithrombin complexes in patients undergoing cardiac surgery with cardiopulmonary bypass.

Main Methods:

• A novel Enzyme-Linked Immunosorbent Assay (ELISA) was employed to measure VIIa-antithrombin complexes.
• Blood samples were collected from 13 adult patients undergoing cardiac surgery.
• Sampling occurred at multiple time points: pre-surgery, post-heparin administration, at 20-minute intervals during cardiopulmonary bypass, and post-protamine.

Main Results:

• Pre-surgery median concentrations of VIIa-antithrombin complexes were 52.7 pM.
• Following a heparin bolus, median concentrations increased to 110 pM and were sustained throughout cardiopulmonary bypass and post-protamine.
• A significant, approximately twofold increase in measurable VIIa-antithrombin complexes was observed after heparin administration during cardiac surgery.

Conclusions:

• Antithrombin plays a significant physiological role in inhibiting Factor VIIa during cardiac surgery.
• The administration of heparin during cardiopulmonary bypass enhances the formation and measurement of VIIa-antithrombin complexes.
• These findings support the active involvement of antithrombin in regulating coagulation during cardiac surgical procedures.