Thrombodynamics Test in Assessing the Risk of Thrombus Formation in Patients with Atrial Fibrillation Taking Direct Oral Anticoagulants

Aim. To evaluate thrombus characteristics in patients with atrial fibrillation (AF) taking different direct oral anticoagulants (DOACs) using Thrombodynamics test.Materials and methods. Thrombodynamics test was performed in 100 patients with paroxysmal and permanent forms of AF taking different DOACs, dose choice was done in accordance with the instructions for drugs use. For analysis samples of fresh citrated platelet-free plasma were taken just before regular DOACs dose intake (trough concentration). Statistical data processing was carried out using R software packages.Results. All patients had no history of thrombosis or bleeding before inclusion in this study. All parameters of Thrombodynamics test taken at residual concentration of DOACs were in general within reference values, that is in the area of normal coagulation: spatial clot growth rate (V) – 26.56 (25.0; 29.2) μm/min, the time to the start of clot growth (Tlag) – 1.05 (0.85; 1.27) min, initial spatial clot growth rate (Vi) – 44.3±7.7 μm/min, stationary spatial clot growth rate (Vst) – 26.5 (24.9; 28.4) μm/min, clot size (CS) – 999.7 (912.9; 1084.7) μm, clot density (D) – 22883.1±3199.9 arb. units. D was appeared to be higher in women [22947.7 (21477.5; 22947.7) vs men [22124.8 (19722.8; 22124.8), p=0.035] and Tlag was significantly higher in patients with chronic heart failure [1.2 (1.0; 1.2) vs 1.0 (0.8; 1.0), p=0.008]. A correlation was found between level of creatinine and Tlag parameter, glomerular filtration rate (GFR) and clot density. With an increase in the level of creatinine in the blood and a decrease in GFR, respectively, there was an increase in Tlag parameter (p-value 0.038); with an increase in GFR, clot density decrease (p-value 0.005).

Conclusion. All parameters of Thrombodynamics test on residual concentration of DOACs were within reference values that indicated optimal anticoagulant effect of all DOACs. The obtained data of normal coagulation at the residual concentration of the anticoagulant are consistent with the previously obtained data on the safety and effectiveness of DOACs using other methods. Further studies with clinical end points are needed to assess the clinical value of this method.

[Comparative efficacy and safety of direct oral anticoagulants in patients with atrial fibrillation and chronic kidney disease]

Aim To compare efficacy and safety of direct oral anticoagulants (DOACs) for prevention of stroke in patients with nonvalvular atrial fibrillation and reduced creatinine clearance.Material and methods Systematic search for literature and indirect comparison of DOACs were performed.Results The indirect comparison included five randomized clinical trials. The DOACs were comparable by the efficacy of preventing stroke and systemic embolism. The safety profiles had differences. Apixaban significantly decreased the relative risk of major bleeding compared to rivaroxaban by 27 % (relative risk (RR) 0.73; 95 % confidence interval (CI): 0.55-0.98). The apixaban advantage was even greater in the group of patients with a creatinine clearance <50 ml/min: RR was reduced by 48 % compared to rivaroxaban (RR=0.52; 95 % CI: 0.32-0.84), by 50 % compared to dabigatran 300 mg/day (RR=0.50; 95 % CI: 0.31-0.81), and by 48 % compared to dabigatran 220 mg/day (RR=0.52; 95 % CI: 0.32-0.85)Conclusion The indirect comparison of DOACs showed that their efficacy was comparable. With respect of safety, apixaban is the preferrable DOAC for patients with atrial fibrillation and creatinine clearance below 50 ml/min.