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)

Introduction: 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 > 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 > 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.