Thrombotic status of patients with atrial fibrillation

BACKGROUND Atrial fibrillation (AF) is associated with increased risk of thrombosis. It is still not fully understood whether AF contributes to only a local prothrombotic state (in the left atrium) or whether this is a systemic phenomenon. Furthermore, it is not known whether restoration of sinus rhythm (SR) with cardioversion or catheter ablation can decrease thrombotic risk over and above that achieved with anticoagulation. The aim of my thesis was to assess the effect of restoration of sinus rhythm on thrombotic status in patients with AF. METHODS We assessed thrombotic status, both peripherally and in the cardiac chambers, in patients with different arrhythmias undergoing radiofrequency catheter ablation (RFCA) with blood samples drawn from the femoral vein and both atria (if applicable). In another study, we investigated the effect of direct current cardioversion (DCCV) and RFCA on global thrombotic status. The peripheral samples were drawn before and 4-6 weeks after DCCV and 3 months after RFCA. The effect of different types of anticoagulation, namely vitamin K antagonist and non-vitamin K oral anticoagulants, on thrombotic status was also assessed. Thrombotic status was assessed with highly physiological, point-of-care Global Thrombosis Test (GTT), which assesses both platelet reactivity (time taken to form an occlusive thrombus - occlusion time, OT) and endogenous thrombolysis (time taken to restore blood flow in the testing column – lysis time, LT) using a native, non-anticoagulated blood sample. RESULTS There were no significant differences in thrombotic status between intra-cardiac and peripheral blood in patients undergoing RFCA. In particular, left atrial blood samples were not more pro-thrombotic than peripheral blood samples in patients with AF. Successful restoration and maintenance of SR with RFCA led to normalization of fibrinolytic profile (as shown by decrease in LT: LT before RFCA: 1994s [1560; 2475] vs. LT after RFCA: 1477s [1015; 1878]; p