Coagulation factors and fibrinolytic activity in the left atrial appendage and other heart chambers in patients with atrial fibrillation: is there a local intracardiac prothrombotic state? (HEART-CLOT study)

Abstract

Atrial fibrillation (AF), a risk factor for stroke and systemic thromboembolism, is associated with unfavorable fibrin clot properties and increased thrombus formation in peripheral blood. The left atrial appendage (LAA) is known to be the primary site of thrombus formation. Aim: We investigated the relative differences in plasma fibrin clot features including plasma fibrin clot permeability (K s ) and clot lysis time (CLT) between the right atrium (RA), right ventricle (RV), left atrium (LA), left ventricle (LV), LAA, and peripheral blood. Methods: Sixteen patients with nonvalvular AF who stopped oral anticoagulant therapy at least 2 days before a LARIAT procedure participated in a single-center prospective study. We measured fibrinogen and plasminogen levels along with K s , CLT, and endogenous thrombin potential (ETP) during the LARIAT procedure in blood obtained from the right femoral vein, RA, RV, LA, LV and LAA. Results: LAA clot porosity was reduced by 16.2% compared to peripheral blood (p = 0.026), also after adjustment for fibrinogen levels (p = 0.038). K s was similar for the RA, RV, LA, LV, and LAA (all p N 0.05). We found 14.7% prolonged CLT for clots prepared from blood samples obtained from the LAA compared to those prepared from peripheral blood, but no differences between the RA, RV, LA and LV (all p N 0.05) were found. There were no significant differences in other parameters, including ETP, between heart chambers. Conclusions: Patients with AF are characterised by a local prothrombotic state as reflected by formation of compact fibrin clots in the LAA compared to peripheral blood, which may contribute to LAA thrombus formation and device-related thrombi.

Case Report: Acute Thrombotic Angiopathy of Atrial Appendage Epicardial Veins: A Seemingly Innocuous Finding Portending a Fatal Outcome

“…While the turbulent flow within the fibrillating atrial appendage is a primary risk factor for the development of a thrombus within the chamber, data suggests that the prothrombotic milieu within the appendage also potentiates thrombus formation (6, 7). Bartus et al illustrated that from direct sampling of blood from within the atrial appendage compared with sampling from other heart chambers revealed a local prothrombotic state with evidence of prolonged clot lysis time and reduced clot porosity (6). Others have also described increased levels of procoagulant factors within the atrial appendage compared with the right atrium and femoral vein, further supporting local activation of the coagulation system (7).…”

Atrial Thrombus and Embolic Stroke in a Patient With Surgical Appendage Ligation and Maze Procedure

“…However, the American College of Cardiology/American Heart Association guidelines do not provide specific guidance on anticoagulation due to the lack of evidence. Discontinuation of oral anticoagulation may be considered in patients who are at increased risk of bleeding undergone successful surgical ablation of AF and LAA excision or exclusion and who remain in sinus rhythm for at least 3 months during which they have been anticoagulated ( 8 ).…”

Why should cardiac surgeons occlude the left atrial appendage percutaneously?

“…In the last decades, the LAAO procedure emerged as an alternative method for stroke prevention 17 . Multiple observational studies point to the feasibility and safety of percutaneous endocardial and epicardial LAAO procedures, and present long‐term effectiveness in thromboembolism and bleeding risk reduction, even in high‐risk patients 16,18‐20 .…”