Endogenous thrombin potential (ETP) in plasma from patients with AMI during antithrombotic treatment

doi:10.1016/j.thromres.2008.03.018

Thrombosis Research

Volume 123, Issue 4, February 2009, Pages 573-579

https://doi.org/10.1016/j.thromres.2008.03.018 Get rights and content

Abstract

Background

The beneficial impact of warfarin in preventing new events after AMI is well established. Decrease in thrombin generation seems to be the key element in anticoagulant treatment.

Objectives

The aims were to investigate the effect of warfarin and platelet inhibition on thrombin generation, assessed by the endogenous thrombin potential (ETP), and study the relation between coagulation parameters and ETP in patients with AMI.

Patients/Methods

In the present sub–study of the WARIS II trial, patients with AMI were randomly assigned to treatment with aspirin 160 mg/d (n = 57), aspirin 75 mg/d and warfarin (INR 2.0–2.5) (n = 68) or warfarin (INR 2.8–4.2) (n = 61). Fasting blood samples were collected from patients at discharge from hospital and after 6 weeks treatment.

Results

Correlation analyses showed that both ETP and peak thrombin levels were significantly correlated with Factor VII Ag (r = 0.38 and 0.36 respectively, p < 0.01 for both) and with F1+2 (r = 0.26 and 0.23 respectively, p = 0.01 for both) at baseline. Antithrombotic treatment for 6 weeks caused a highly significant inhibition of ETP in patients treated with warfarin (− 28% ± 5%, p < 0.001), and patients treated with aspirin/warfarin (− 24% ± 8%, p = 0.04). Similarly, peak thrombin levels were reduced in patients treated with warfarin (− 18% ± 7%, p = 0.049) and aspirin/warfarin (− 19% ± 5%, p = 0.029), whereas an increase (12% ± 4%, p = 0.029) occurred during aspirin treatment alone. F1+2 levels decreased by 64% and 58% in the warfarin and aspirin/warfarin groups, respectively (p = 0.001 for both).

Conclusions

In patients with AMI, warfarin significantly reduced the endogenous thrombin generation and the potential to generate thrombin in plasma ex vivo, whereas aspirin alone had no effect on thrombin generation in vivo or ex vivo, assessed by ETP.

Introduction

Plaque disruption with subsequent thrombin generation and superimposed thrombosis is the main cause of acute coronary events [1]. Thrombin formation enhance the activation of the coagulation cascade, platelet activation and may also contribute to the development of the atheromatous lesion itself [2], [3].

Prothrombin fragment 1+2 (F1+2) is a specific molecular marker of thrombin generation in the body. Circulating levels have previously been reported to be a marker of both acute venous and arterial thrombotic events [4], [5] and also to be a predictor for new thrombotic events and mortality [6], [7]. Growing evidence support the concept that tissue factor (TF)–induced thrombin formation in plasma ex vivo by the endogenous thrombin potential (ETP), and notably parameters of the thrombogram, are useful in assessing the risk of bleeding, thrombosis and anticoagulant treatment [8]. The calibrated automated thrombogram (CAT) method displays the thrombin activity over time in clotting plasma. This is monitored by a fluorescent product released by cleavage of a flourogenic substrate and calibrated by comparison with a known thrombin activity in a parallel non–clotting sample [9]. Thus, the thrombogram allow assessment of the initiation phase (lag–time) and propagation phase (endogenous thrombin potential–ETP) of coagulation. As clotting occurs at the start of the explosive burst of thrombin formation, clotting times is a good estimate of the duration of the lag phase, whereas ETP reflects the potential thrombin–forming capacity of a non–triggered system in any given situation, e.g. at site of plaque disruption.

Aspirin inhibits thromboxane–induced platelet activation by irreversible inhibition of cyclooxygenase [10], whereas warfarin inhibits the vitamin K–dependent post–translational carboxylation of glutamate residues on the N–terminal regions of coagulation factors II, VII, IX and X by inhibiting the conversion of vitamin K 2, 3–epoxide to reduced vitamin K [11]. Several randomized controlled studies have reported superior efficacy in secondary prevention of fatal and non–fatal MI and stroke of oral anticoagulant treatment alone or in combination with antiplatelet treatment over antiplatelet treatment alone in survivors of acute myocardial infarction (AMI) [12], [13], [14], [15]. Warfarin treatment is reported to decrease factor VII coagulant activity (FVIIc) [16], [17] and factor VII mass (FVIIAg) [18], whereas activated factor VII (FVIIa) are reported unchanged [19] or decreased [20] in patients on anticoagulant treatment. The aims of the present study were to investigate the effect of warfarin and aspirin treatment on thrombin generation, assessed by the ETP, and study the relation between coagulation parameters and ETP in patients with AMI.

Section snippets

Study population and design

This is a part of the WARIS–II trial [13], a national multicenter study in which patients with an AMI were randomly assigned to treatment with warfarin alone (Marevan^®, Nycomed Pharma, Asker, Norway) with target INR 2.8–4.2, aspirin alone (Albyl–E^®, Nycomed Pharma) 160 mg d^–1 or aspirin 75 mg d^–1 and warfarin with target INR 2.0–2.5. Randomization was stratified by centre. The study protocol was approved by the Regional Ethics Committee and all patients gave written informed consent for the

Results

Baseline characteristics of the study population are given in Table 1. Mean age was 61.4 years and 78% of the patients were men. The three treatment groups were comparable with respect to all the listed variables except for the prevalence of diabetes which was significantly higher in the group of patients receiving combined aspirin and warfarin treatment. The mean INRs (range) obtained in patients treated with warfarin alone were 3.0 (1.9–5.5) and 2.3 (1.3–4.1) in those receiving combined

Discussion

The present study shows a significant reduction of thrombin generation both in vivo, assessed by the levels of F1+2, and ex vivo, assessed by ETP, during 6 weeks anticoagulant treatment with warfarin after an AMI. Thrombin formation is known to play a crucial role in coagulation as well as platelet activation with subsequent thrombus formation during acute coronary events [22]. Thus, it is likely to assume that inhibited thrombin generation during warfarin treatment contributed substantially to

Acknowledgements

CART is supported by an independent grant from Pfizer.

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The thrombin generation curve is quantified in terms of the lag time, time to peak thrombin generation, peak thrombin generation, and endogenous thrombin potential (ETP), which is the area under the curve. Warfarin reduces the ETP by 30–50% of that before warfarin or that in normal controls.10,11 Rivaroxaban inhibits thrombin generation in whole blood and platelet-rich plasma,12 and the ETP may be used as a measure of anticoagulation intensity.13,14
Rivaroxaban is established for the treatment and secondary prevention of venous thromboembolism, but whether it is useful in patients with antiphospholipid syndrome is uncertain.
This randomised, controlled, open-label, phase 2/3, non-inferiority trial, done in two UK hospitals, included patients with antiphospholipid syndrome who were taking warfarin for previous venous thromboembolism, with a target international normalised ratio of 2·5. Patients were randomly assigned 1:1 to continue with warfarin or receive 20 mg oral rivaroxaban daily. Randomisation was done centrally, stratified by centre and patient type (with vs without systemic lupus erythematosus). The primary outcome was percentage change in endogenous thrombin potential (ETP) from randomisation to day 42, with non-inferiority set at less than 20% difference from warfarin in mean percentage change. Analysis was by modified intention to treat. Other thrombin generation parameters, thrombosis, and bleeding were also assessed. Treatment effect was measured as the ratio of rivaroxaban to warfarin for thrombin generation. This trial is registered with the ISRCTN registry, number ISRCTN68222801.
Of 116 patients randomised between June 5, 2013, and Nov 11, 2014, 54 who received rivaroxaban and 56 who received warfarin were assessed. At day 42, ETP was higher in the rivaroxaban than in the warfarin group (geometric mean 1086 nmol/L per min, 95% CI 957–1233 vs 548, 484–621, treatment effect 2·0, 95% CI 1·7–2·4, p<0·0001). Peak thrombin generation was lower in the rivaroxaban group (56 nmol/L, 95% CI 47–66 vs 86 nmol/L, 72–102, treatment effect 0·6, 95% CI 0·5–0·8, p=0·0006). No thrombosis or major bleeding were seen. Serious adverse events occurred in four patients in each group.
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Regular ArticleEndogenous thrombin potential (ETP) in plasma from patients with AMI during antithrombotic treatment

Abstract

Background

Objectives

Patients/Methods

Results

Conclusions

Introduction

Section snippets

Study population and design

Results

Discussion

Acknowledgements

Atherosclerosis

Clin Haematol

Prog Cardiovasc Dis

J Am Coll Cardiol

Thromb Res

Blood

J Thromb Haemost

Lancet

Blood

Blood

J Thromb Haemost. Ref Type: Generic

J Am Coll Cardiol

Blood

Thromb Res

Prognostic significance of markers of thrombin generation in the acute and chronic phases of non cardioembolic ischemic stroke

Minerva Cardioangiol

Laboratory methods in the haemostatic laboratory

Thromb Haemost

Regular Article
Endogenous thrombin potential (ETP) in plasma from patients with AMI during antithrombotic treatment