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

Julia S Gauer,Nicoletta Riva,Eden M Page,Helen Philippou,Michael Makris,Alex Gatt,Robert A.S Ariëns

doi:10.1002/rth2.12443

Abstract

BackgroundAbnormal clot structure has been identified in patients with thrombotic disorders. Anticoagulant therapy offers clear benefits for thrombosis prevention and treatment by reducing blood clot formation and size; nevertheless, there are limited data on the effects of different anticoagulants, where clotting is initiated with different triggers, on clot structure. ObjectivesOur aim was to investigate the effects of vitamin K antagonists and factor Xa inhibitors on clot structure. MethodsClots from pooled plasma spiked with rivaroxaban, apixaban, or enoxaparin, as well as plasma from patients on warfarin, were compared to plasma without anticoagulation. The kinetic profile of polymerizing clots was obtained by turbidity, fiber density was determined by confocal microscopy, clot pore size was investigated by permeation, and fiber size was analyzed using scanning electron microscopy. Clotting agonist was either tissue factor or thrombin. ResultsFollowing clotting with tissue factor, all anticoagulated clots had a significantly increased lag time, with the exception of enoxaparin. Rivaroxaban additionally led to significantly less dense and more permeable clots, with thicker fibers. In contrast, turbidity analysis following initiation with thrombin showed few effects of anticoagulation, with only enoxaparin leading to a prolonged lag time. Enoxaparin clots made with thrombin were less dense and more permeable. ConclusionOur results show that anticoagulants modulate clot structure particularly when induced by tissue factor, most likely due to reduction of thrombin generation. We propose that the effects of different anticoagulants could be assessed with a global clot structure measurement such as permeation or turbidity, providing information on clot phenotype.

Highlights

Thrombosis is a major contributor to global disease burden, being a serious and lethal component of cardiovascular diseases such as ischemic heart disease, stroke, and venous thromboembolism.[1,2] Thromboembolic conditions accounted for one in four deaths worldwide in 2010 and remain the leading cause of death around the world.[3,4,5,6] Anticoagulants decrease blood clot formation by targeting and modulating the coagulation pathway and are, commonly administered to prevent and treat thromboembolic disorders.[7]
We compared clot structure in plasma from individuals on warfarin, pooled plasma (PP) spiked with the direct FXa inhibitors rivaroxaban and apixaban, and PP spiked with the indirect FXa inhibitor enoxaparin, to PP control using a range of sensitive methods that analyze clot density, porosity, and fiber thickness
Our study provides a novel systematic and comprehensive direct comparison of alterations on fibrin clot structure, caused by different classes of anticoagulants, detected with an array of different sensitive methods

Summary

| INTRODUCTION

Thrombosis is a major contributor to global disease burden, being a serious and lethal component of cardiovascular diseases such as ischemic heart disease, stroke, and venous thromboembolism.[1,2] Thromboembolic conditions accounted for one in four deaths worldwide in 2010 and remain the leading cause of death around the world.[3,4,5,6] Anticoagulants decrease blood clot formation by targeting and modulating the coagulation pathway and are, commonly administered to prevent and treat thromboembolic disorders.[7]. Thrombus growth and fibrin distribution patterns, related to clot stability, have been studied with TF-bearing collagen surfaces.[27,28] TF has been reported to better reflect effects of VKAs on clot density and permeability.[29] In this study, we compared clot structure in plasma from individuals on warfarin, pooled plasma (PP) spiked with the direct FXa inhibitors rivaroxaban and apixaban, and PP spiked with the indirect FXa inhibitor enoxaparin, to PP control using a range of sensitive methods that analyze clot density, porosity, and fiber thickness. We used a comprehensive set of clot structure analysis methods to directly compare the effects of VKAs and indirect/direct FXa inhibitors on fibrin clot structure when clotting was triggered with either thrombin or TF

| MATERIALS AND METHODS

Findings

| DISCUSSION