The primary objective of this study is to prospectively investigate hemostatic activity following transcatheter left atrial appendage occlusion (LAAO).

This is a prospective cohort study of patients undergoing transcatheter LAAO at Aarhus University Hospital. Hemostatic consequences following device implantation will be evaluated using blood samples collected pre- and post-procedurally, and serially during three months follow-up in 135 LAAO patients. Platelet function and characteristics, overall activation of the extrinsic coagulation pathway and the intrinsic contact activation pathway, as well as endothelial response to implantation, will be assessed through a wide range of biochemical analyses. Patients will serve as their own controls, with a final control blood sample collected at three-months follow-up.

Inclusion Criteria:

• Age > 18 years
• Atrial fibrillation (paroxysmal, persistent, or permanent)
• Admitted and eligible for LAAO
• Signed written consent

Exclusion Criteria:

• Known hereditary bleeding disorders (i.e. Hemophilia A and B, Von Willebrand disease)
• Platelet count < 75 x 109/ml

Only patients already eligible for LAAO will be screened by clinical personnel and potentially recruited for participation. Blood samples will be systematically sampled during planned follow-up timepoints.