Factor Xa inhibition by rivaroxaban in the trough steady state can significantly reduce thrombin generation

Coagulation markers in patients with venous thromboembolism treated with 10 mg apixaban twice daily

Apixaban is used to treat venous thromboembolism (VTE) at 10 mg twice daily (BID) for 7 days, followed by 5 mg BID without dose adjustment, and non-valvular atrial fibrillation (NVAF) at 5 mg BID or 2.5 mg BID with dose adjustment criteria (DAC) including age, body weight, and renal function. The anti-factor Xa activity (AXA), prothrombin time (PT), and activated partial thromboplastin time (APTT) in patients with VTE receiving 10 mg BID of apixaban remains unclear. Twenty-six patients (70.8±15.4 years, 10 males) with VTE receiving 10 mg BID of apixaban were enrolled. The patients were divided into two groups based on whether they met the DAC of NVAF: DAC group (n=8) and non-DAC group (n=18). Trough and peak AXA values, PT, and APTT were measured at 10 mg BID dosage and then at 5 mg BID dosage. Coagulation markers in recipients of 10 mg BID therapy were significantly higher than those of 5 mg BID recipients. A significant and strong positive correlation was observed between AXA and PT at trough and peak times. The AXA values and PT in the DAC group were significantly higher than those in the non-DAC group. No significant inter-group differences were seen in APTT. This study provides the first report of AXA distribution in VTE patients receiving 10 mg BID of apixaban. Our findings indicate that coagulation markers may differ in patients with VTE-prescribed higher doses of apixaban and a DAC may be warranted in such patients.

Altered fibrin clot properties and fibrinolysis in patients with atrial fibrillation: practical implications

Compelling evidence indicates that a hypercoagulable state occurs in patients with atrial fibrillation (AF) including those in sinus rhythm following paroxysmal and persistent AF. Activation of blood coagulation in AF reflects heightened thrombin generation with the subsequent increased formation of fibrin as evidenced by elevated soluble fibrin monomers and D-dimer. Formation of denser fibrin meshworks, relatively resistant to plasmin-mediated lysis has been demonstrated in patients with AF. The presence of stroke risk factors in AF, such as diabetes, heart failure, hypertension, previous myocardial infarction, or stroke, advanced age have been shown to be linked to the prothrombotic clot characteristics, including reduced clot permeability and lysability. Importantly, biomarkers, including cardiac troponins and N-terminal pro-brain natriuretic peptide, are associated with thrombin generation and fibrin-related markers in AF patients. Recently, increased fibrin clot density (low clot permeability measured in plasma-based assays) and impaired fibrinolysis measured off anticoagulation have been demonstrated to predict ischaemic cerebrovascular events in patients with AF receiving vitamin K antagonists and those on rivaroxaban. The current review summarizes evidence for a role of altered fibrin clot properties and hypofibrinolysis in AF and their prognostic value in terms of adverse events.

Effects of rivaroxaban and dabigatran on global hemostasis in patients with atrial fibrillation

: The study was aimed to evaluate the effects of two standard doses of rivaroxaban and dabigatran on global hemostatic assays in patients with atrial fibrillation. The study included 52 patients treated with rivaroxaban (15/20 mg), 50 on dabigatran (110/150 mg) and 20 healthy individuals. Platelet-poor plasma was used for determination of three global hemostatic assays, namely endogenous thrombin potential (ETP), calibrated automated thrombogram (CAT) and overall hemostasis potential (OHP). Rivaroxaban and dabigatran reduced ETP (P < 0.01) although OHP (P < 0.05) was diminished only by dabigatran. Strong correlations were noticed between ETP parameters and the plasma concentrations of rivaroxaban (ETP, r = -0.51; c-max, r = -0.85; t-lag, r = 0.83; t-max, r = 0.66) as well as with plasma concentration of dabigatran (ETP, r = -0.75; c-max, r = -0.74; t-lag, r = 0.73; t-max, r = 0.52). Analysis of dabigatran concentrations under 50 ng/ml showed that ETP parameter has area under the concentration-time curve-receiver operating characteristic value of 0.879 (95% confidence interval 0.776-0.980). Dabigatran treatment paradoxically increased area under the concentration-time curve and peak values although rivaroxaban decreased peak values (P < 0.01). However, significant correlation between CAT parameters and plasma concentration of both direct oral anticoagulants was not observed. We confirmed that the CAT assay is inappropriate for estimation of dabigatran effects and is not fully sensitive as regards rivaroxaban. The ETP assay can potentially be the appropriate method for estimation of global hemostatic capacity as regards both direct oral anticoagulants. The role of OHP needs to be confirmed in additional studies. ETP parameter of chromogenic assay has promising potential in exclusion of high plasma concentrations of dabigatran.

Association Between Low-Dose Rivaroxaban With or Without Aspirin and Ischemic Stroke Subtypes: A Secondary Analysis of the COMPASS Trial

Importance

The COMPASS (Cardiovascular Outcomes for People Using Anticoagulation Strategies) randomized clinical trial was stopped early owing to the efficacy of low-dose rivaroxaban plus aspirin in preventing major cardiovascular events. The main reason for early trial termination was the effect of combination therapy on reducing ischemic strokes.

Objective

To analyze the association between low-dose rivaroxaban with or without aspirin and different ischemic stroke subtypes.

Design, Setting, and Participants

This is a secondary analysis of a multicenter, double-blind, randomized, placebo-controlled study that was performed in 33 countries from March 12, 2013, to May 10, 2016. Patients with stable atherosclerotic vascular disease were eligible, and a total of 27 395 participants were randomized and followed up to February 6, 2017. All first ischemic strokes and uncertain strokes that occurred by this date were adjudicated using TOAST (Trial of Org 10172 in Acute Stroke Treatment) criteria. The analysis of ischemic stroke subtypes was evaluated using an intention-to-treat principle. Statistical analysis was performed from March 12, 2013, to February 6, 2017.

Interventions

Participants received rivaroxaban (2.5 mg twice a day) plus aspirin (100 mg once a day), rivaroxaban (5 mg twice a day), or aspirin (100 mg once a day).

Main Outcomes and Measures

Risk of ischemic stroke subtypes during follow-up.

Results

A total of 291 patients (66 women; mean [SD] age, 69.4 [8.5] years; 43 [14.8%] had a previous nonlacunar stroke) experienced an ischemic stroke. During the study, 49 patients (16.8%) received a diagnosis of atrial fibrillation. Applying TOAST criteria, 59 strokes (20.3%) were cardioembolic, 54 strokes (18.6%) were secondary to greater than 50% stenosis of the ipsilateral internal carotid artery, 42 strokes (14.4%) had a negative evaluation that met criteria for embolic stroke of undetermined source, and 21 strokes (7.2%) were secondary to small vessel disease. There were significantly fewer cardioembolic strokes (hazard ratio [HR], 0.40 [95% CI, 0.20-0.78]; P = .005) and embolic strokes of undetermined source (HR, 0.30 [95% CI, 0.12-0.74]; P = .006) in the combination therapy group compared with the aspirin-only group. A trend for reduction in strokes secondary to small vessel disease (HR, 0.36 [95% CI, 0.12-1.14]; P = .07) was not statistically significant. No significant difference was observed between the 2 groups in strokes secondary to greater than 50% carotid artery stenosis (HR, 0.85 [95% CI, 0.45-1.60]; P = .61). Rivaroxaban, 5 mg, twice daily showed a trend for reducing cardioembolic strokes compared with aspirin (HR, 0.57 [95% CI, 0.31-1.03]; P = .06) but was not associated with reducing other stroke subtypes.

Conclusions and Relevance

For patients with systemic atherosclerosis, low-dose rivaroxaban plus aspirin was associated with large, significant reductions in cardioembolic strokes and embolic strokes of undetermined source. However, these results of exploratory analysis need to be independently confirmed before influencing clinical practice.

Trial Registration

ClinicalTrials.gov identifier: NCT01776424.

Reduced Rivaroxaban Dose Versus Dual Antiplatelet Therapy After Left Atrial Appendage Closure

Background:

Percutaneous left atrial appendage closure (LAAC) exposes to the risk of device thrombosis in patients with atrial fibrillation who frequently have a contraindication to full anticoagulation. Thereby, dual antiplatelet therapy (DAPT) is usually preferred. No randomized study has evaluated nonvitamin K antagonist oral anticoagulant after LAAC, and we decided to evaluate the efficacy and safety of reduced doses of rivaroxaban after LAAC.

Methods:

ADRIFT (Assessment of Dual Antiplatelet Therapy Versus Rivaroxaban in Atrial Fibrillation Patients Treated With Left Atrial Appendage Closure) is a multicenter, phase IIb study, which randomized 105 patients after successful LAAC to either rivaroxaban 10 mg (R 10 , n=37), rivaroxaban 15 mg (R 15 , n=35), or DAPT with aspirin 75 mg and clopidogrel 75 mg (n=33). The primary end point was thrombin generation (prothrombin fragments 1+2) measured 2 to 4 hours after drug intake, 10 days after treatment initiation. Thrombin-antithrombin complex, D-dimers, rivaroxaban concentrations were also measured at 10 days and 3 months. Clinical end points were evaluated at 3-month follow-up.

Results:

The primary end point was reduced with R 10 (179 pmol/L [interquartile range (IQR), 129–273], P <0.0001) and R 15 (163 pmol/L [IQR, 112–231], P <0.0001) as compared with DAPT (322 pmol/L [IQR, 218–528]). We observed no significant reduction of the primary end point between R 10 and R 15 while rivaroxaban concentrations increased significantly from 184 ng/mL (IQR, 127–290) with R 10 to 274 ng/mL (IQR, 192–377) with R 15 , P <0.0001. Thrombin-antithrombin complex and D-dimers were numerically lower with both rivaroxaban doses than with DAPT. These findings were all confirmed at 3 months. The clinical end points were not different between groups. A device thrombosis was noted in 2 patients assigned to DAPT.

Conclusions:

Thrombin generation measured after LAAC was lower in patients treated by reduced rivaroxaban doses than DAPT, supporting an alternative to the antithrombotic regimens currently used after LAAC and deserves further evaluation in larger studies.

Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT03273322.

Combination therapy with an Xa inhibitor and antihypertensive agent improved anticoagulant activity in patients with nonvalvular atrial fibrillation: the hypertension and atrial fibrillation treated by rivaroxaban for the morning and night with sYnergy with calcium antagonists (HARMONY) study

Background: Anticoagulant activity and blood pressure increase in the morning. The aim of this study was to evaluate changes of anticoagulant activity, blood pressure and target organ damage in patients with nonvalvular atrial fibrillation (AF) given combination treatment with Xa inhibitor and antihypertensive agent.Methods: We enrolled 72 patients with nonvalvular AF. Rivaroxaban (10-15 mg) was continuously administered once daily over 8 weeks (study period I). For subjects (n = 50) who exhibited uncontrolled morning hypertension (home systolic blood pressure [SBP]≥125 mmHg) at the end of study period I (at 8 weeks), nifedipine CR (20-40 mg) was added at bedtime, and rivaroxaban administration was continued an additional 8 weeks. We assessed prothrombin fragment 1 + 2 (optimal range: 69-229 pmol/L) and D-dimer (negative D-dimer measurement: <1.0 μg/mL).Results: The percentage of patients with optimal-range prothrombin fragment 1 + 2 was significantly increased at 4 weeks compared to baseline (70.8% vs. 86.1%, p = .033). In period II, office and home morning SBP were reduced at 12 compared to 8 weeks (office SBP: 135.2 ± 15.7 vs. 125.6 ± 18.4mmHg, p < .001; home morning SBP: 133.5 ± 10.5 vs. 119.9 ± 12.1mmHg, p<.001).The percentage of patients with negative D-dimer  was increased at 8 weeks compared to baseline (92% vs. 100%, p = .044), and remained at 100% at 16 weeks.Conclusions: Xa inhibitor therapy improved anticoagulant activity, and additional antihypertensive therapy maintained the anticoagulant activity in patients with nonvalvular AF.

Monitoring the roles of prothrombin activation fragment 1 and 2 (F1 + 2) in patients with atrial fibrillation receiving rivaroxaban and apixaban

Factor Xa (FXa) inhibitors are recommended for use in fixed doses without laboratory monitoring. However, prior studies reported the importance of establishing biomarkers representing anticoagulation intensity related to bleeding or thrombotic events. To test the hypothesis that prothrombin activation fragment 1 and 2 (F1 + 2), a non-specific marker of thrombin generation, could be altered during FXa inhibitor treatment in patients with atrial fibrillation. We conducted the study in two different clinical settings. First, the interrelations among biomarkers representing coagulation/fibrinolysis were investigated in 80 patients in an outpatient clinic. Second, these biomarkers were evaluated in 75 patients who underwent radiofrequency catheter ablation. Plasma concentration of FXa inhibitors was evaluated using an anti-FXa chromogenic assay (C-Xa). In the outpatient study, only F1 + 2 exhibited a significant and negative association with C-Xa (rS =  - 0.315, p = 0.026), and 37% of the variance could be explained by C-Xa levels. F1 + 2 levels above the reference range (> 229 pmol/L) could be considered as a cut-off to identify poor patient compliance or under-dosing. In the peri-ablation study, increased F1 + 2 levels were associated with decline of C-Xa levels after periprocedural discontinuation of FXa inhibitors, which was greater in the rivaroxaban group than in the apixaban group. F1 + 2 showed modest and inverse association with plasma concentration of rivaroxaban and apixaban in patients with atrial fibrillation. Larger study to test the hypothesis that continued thrombin generation despite anticoagulation is associated with a heightened risk of clinical events is required.

Effects of Rivaroxaban on Biomarkers of Coagulation and Inflammation: A Post Hoc Analysis of the X-VeRT Trial

Introduction  This X-VeRT (eXplore the efficacy and safety of once-daily oral riVaroxaban for the prevention of caRdiovascular events in patients with nonvalvular aTrial fibrillation scheduled for cardioversion) substudy evaluated the effects of treatment with rivaroxaban or a vitamin-K antagonist (VKA) on levels of biomarkers of coagulation (D-dimer, thrombin–antithrombin III complex [TAT] and prothrombin fragment [F1.2]) and inflammation (high sensitivity C-reactive protein [hs-CRP] and high-sensitivity interleukin-6 [hs-IL-6]) in patients with atrial fibrillation (AF) who were scheduled for cardioversion and had not received adequate anticoagulation at baseline (defined as, in the 21 days before randomization: no oral anticoagulant; international normalized ratio <2.0 with VKA treatment; or <80% compliance with non-VKA oral anticoagulant treatment).

Methods  Samples for biomarker analysis were taken at baseline ( n  = 958) and treatment completion (42 days after cardioversion; n  = 918). The influence of clinical characteristics on baseline biomarker levels and the effect of treatment on changes in biomarker levels were evaluated using linear and logistic models.

Results  Baseline levels of some biomarkers were significantly associated with type of AF (D-dimer and hs-IL-6) and with history of congestive heart failure (hs-CRP, D-dimer, and hs-IL-6). Rivaroxaban and VKA treatments were associated with reductions from baseline in levels of D-dimer (−32.3 and −37.6%, respectively), TAT (−28.0 and −23.1%, respectively), hs-CRP (−12.5 and −17.9%, respectively), and hs-IL-6 (−9.2 and −9.8%, respectively). F1.2 levels were reduced from baseline in patients receiving a VKA (−53.0%) but not in those receiving rivaroxaban (2.7%).

Conclusion  Anticoagulation with rivaroxaban reduced levels of key inflammation and coagulation biomarkers to a similar extent as VKAs, with the exception of F1.2. Further investigation to confirm the value of these biomarkers in patients with AF is merited.

LongShengZhi Capsule reduces carrageenan-induced thrombosis by reducing activation of platelets and endothelial cells

Formation of thrombosis is associated with activation of platelets and endothelial cells. The effect of LongShengZhi Capsule (LSZ), a traditional Chinese medicine used for treatment of vascular diseases, on thrombosis was investigated in this study. BALB/c mice were induced thrombosis by injection of carrageenan while receiving pre or simultaneous LSZ treatment. We also compared the therapeutic effects of LSZ and clopidogrel on formed thrombi. LSZ inhibited carrageenan-induced thrombi in mouse tissue vessels. In addition, LSZ but not clopidogrel reduced formed thrombi with a short time window. The reduction of thrombi by LSZ was associated with reduced serum P-selectin, reduced expression of TNF-α and P-selectin and activated matrix metalloproteinase 2 expression in tissues. In vitro, LSZ decreased thrombin-induced human platelet clot retraction which was associated with inactivation of AKT and ERK1/2. LSZ also reduced adhesion of platelets or THP-1 monocytes to human umbilical vein endothelial cells (HUVECs) induced by oxidized low-density lipoprotein or lipopolysaccharide. The anti-adherent actions of LSZ was attributed to reduction of oxidative stress, expression of platelet receptors (P2Y₁₂, PAR4 and CD36) and AKT activity in platelets. LSZ also reduced adhesion molecules or tissue factor but activated tissue factor pathway inhibitor expression in HUVECs. Taken together, our study demonstrates the antithrombotic properties of LSZ by reducing activation of platelets and endothelial cells, and suggests its potential application in clinics.

Factor Xa inhibition by rivaroxaban in the trough steady state can significantly reduce thrombin generation

AIMS

The aim of the present study was to demonstrate evidence of reduced thrombin generation at the trough plasma rivaroxaban concentration.

METHODS

A single-centre, prospective, nonrandomized, drug-intervention, self-controlled study was conducted in 51 anticoagulation therapy-naïve patients with nonvalvular atrial fibrillation. Plasma rivaroxaban concentration was measured by liquid chromatography tandem mass spectrometry (LC-MS/MS) and the anti-factor Xa chromogenic assay. Partial thrombin time (PT), protein C activity, and protein S antigen, prothrombin fragment 1 + 2 (F1 + 2), D-dimer, thrombomodulin (TM), thrombin-antithrombin complex (TAT), plasminogen activator inhibitor-1 (PAI-1) and tissue factor pathway inhibitor (TFPI) levels were also measured at the trough steady state after 4 weeks of rivaroxaban treatment and compared with baseline.

RESULTS

Plasma concentrations obtained by the LC-MS/MS and anti-Xa assays were correlated (r = 0.841, P < 0.001). The mean concentration of rivaroxaban at the trough steady state was 23.6 ng ml^-1 , at which F1 + 2, TAT and D-dimer had decreased from the baseline values (P < 0.0001, P = 0.029 and P < 0.005, respectively). PT was prolonged (+0.59 s, P < 0.0001). TFPI increased from baseline to the trough steady state in the first to third quartile groups (+0.79 pg ml^-1 , P = 0.048). By contrast, PAI-1, protein C activity, protein S antigen and TM remained within the normal range at the trough steady state.

CONCLUSIONS

Residual plasma rivaroxaban at the trough steady state may explain the antithrombin effect of rivaroxaban in patients with nonvalvular atrial fibrillation.