Plasma clot formation and clot lysis to compare effects of different anticoagulation treatments on hemostasis in patients with atrial fibrillation

Abstract

The effect of direct oral anticoagulants (DOACs) on turbidimetric measurements of plasma clot formation and susceptibility to fibrinolysis may facilitate a comparison between different classes of anticoagulants in plasma samples. We obtained 424 citrate plasma samples from 226 atrial fibrillation patients on anticoagulation and 24 samples without anticoagulation serving as controls. As comparators, we measured the international normalized ratio (INR) for phenprocoumon samples (N = 166), anti-Xa for low molecular weight heparin (LMWH) samples (N = 42), and DOAC levels with mass spectrometry (dabigatran N = 40, rivaroxaban N = 110, apixaban N = 42). Plasma clot formation and lysis were recorded continuously on a photometer after addition of an activation mix (tissue factor 2 pmol/l and tissue plasminogen activator 333 ng/ml). We used linear regression and ANCOVA for correlation analysis. Clot formation lag phase was prolonged in the presence of anticoagulants in a concentration-dependent manner for DOACs (dabigatran Spearman r = 0.74; rivaroxaban r = 0.78; apixaban r = 0.72, all p < 0.0001), INR dependent for phenprocoumon (r = 0.59, p < 0.0001), anti-Xa level dependent in LMWH samples (r = 0.90, p < 0.0001). Maximum rate of clot formation and peak clot turbidity were reduced in the presence of anticoagulants, but correlated only moderately with the comparator measures of anticoagulation. The clot lysis time was inversely correlated with DOAC concentrations in the presence of recombinant thrombomodulin. A direct ex vivo comparison between the effects of different classes of anticoagulants is possible with turbidimetric measurement of plasma clot formation and lysis. Anticoagulation inhibited clot formation in a plasma concentration manner for DOACs, INR dependent for phenprocoumon, and anti-Xa dependent for LMWH. Susceptibility to fibrinolysis increased with increasing DOAC concentrations.

2021 Update of the International Council for Standardization in Haematology Recommendations for Laboratory Measurement of Direct Oral Anticoagulants

“…58 Additionally, it has been shown that dabigatran, rivaroxaban, and apixaban enhance fibrinolysis, but this depends on the presence of thrombomodulin in the test system. [59][60][61][62] As such, caution should be used when performing and interpreting the results from any coagulation-related test from a DOAC-treated patient. 37…”

Effect of anticoagulants on fibrin clot structure: A comparison between vitamin K antagonists and factor Xa inhibitors

“…16,17 In addition, anticoagulants have been shown to delay clotting lag time and increase the efficiency of clot lysis. 11,[18][19][20][21] The effects of anticoagulants on clot structure have been previously investigated using thrombin 12,13,15,22 or tissue factor (TF), 11,14,16,17,[19][20][21]23,24 as well as TF-bearing cells 25,26 as clotting agonists. In addition, thrombus growth and fibrin distribution patterns, related to clot stability, have also been studied with TF-bearing collagen surfaces.…”

“…Direct thrombin inhibitors have also been shown to delay thrombin generation and increase clot permeability 16,17 . In addition, anticoagulants have been shown to delay clotting lag time and increase the efficiency of clot lysis 11,18‐21 …”

Fibrinolysis in Acute and Chronic Cardiovascular Disease

“…90 In one study measuring ex vivo plasma clots from patients with atrial fibrillation by turbidimetric analysis, dabigatran and factor Xa inhibitors delayed clot formation and modestly decreased clot firmness. 91 In contrast, another study scrutinizing thrombin generation and clot firmness in whole-blood and plasma by using TEG from eight heathy volunteers demonstrated that while both FXa inhibitors and dabigatran effectively prolonged thrombin generation, neither altered clot firmness. 92 These findings resembled the results from another double-blinded, placebo, randomized controlled trial (RCT) that included 35 CAD patients on DAPT with aspirin and clopidogrel.…”