A systematic review and Bayesian network meta‐analysis of risk of intracranial hemorrhage with direct oral anticoagulants

Essentials

• Risk of intracranial hemorrhage (ICH) may differ between direct oral anticoagulants (DOACs).
• We compared the risk of ICH between DOACs using network meta‐analysis.
• Dabigatran 110 mg and 150 mg were safer than rivaroxaban on Bayesian analysis.
• Dabigatran 110 mg ranked as the safest DOAC while rivaroxaban ranked last.

Summary

Background

The comparative risk of intracranial hemorrhage (ICH) among direct oral anticoagulants (DOACs) (dabigatran, rivaroxaban, apixaban and edoxaban) remains unclear.

Objective

To determine the difference in risk of ICH between DOACs

Methods

Seventeen randomized controlled trials (RCTs) were selected using PubMed/MEDLINE, EMBASE and CENTRAL (Inception, 31 December 2017). Estimates were reported as odds ratio (OR) with 95% credible interval (CR.I) in Bayesian network meta‐analysis (NMA), and OR with 95% confidence interval (CI) in traditional meta‐analyses. Relative ranking probability of each group was generated based on surface under the cumulative ranking curve (SUCRA).

Results

In NMA of 116 618 patients from 17 RCTs (apixaban = 19 495 patients, rivaroxaban = 14 157 patients, dabigatran = 16 074 patients, edoxaban = 11 652 patients, and comparator = 55 315 patients), all DOACs were safer than warfarin for risk of ICH. Dabigatran 110 mg ranked as the safest drug (SUCRA, 0.85) and reduced the risk of ICH by 56% compared to rivaroxaban (OR, 0.44; 95% Cr.I, 0.22–0.82). Pairwise meta‐analysis validated these findings, showing that DOACs were safer than warfarin (OR, 0.46; 95% CI, 0.35–0.59). Subgroup analysis showed that the benefit was present when DOACs were used in non‐valvular atrial fibrillation (NVAF) (OR, 0.51; 95% CI, 0.38–0.68) or venous thromboembolism (VTE) (OR, 0.32; 95% CI, 0.18–0.58).

Conclusion

Dabigatran 110 mg may be the safest choice among any anticoagulant regarding risk of ICH. Both dabigatran 110 mg and 150 mg were safer than rivaroxaban.

     

Dabigatran versus vitamin k antagonist: an observational across‐cohort comparison in acute coronary syndrome patients with atrial fibrillation

Essentials

• Acute coronary syndrome (ACS) with atrial fibrillation (AF) is a therapeutic challenge.
• Dual and triple antithrombotic therapy showed a similar thrombotic risk in ACS patients with AF.
• The omission of aspirin during the first month did not increase the rate of ischemic events.
• Replacement of vitamin K antagonist by dabigatran leads to an increased thrombotic risk.

Summary

Background

Dual antithrombotic therapy comprising a vitamin K antagonist (VKA) plus clopidogrel reduces the incidence of major bleeding compared with triple therapy (VKA + clopidogrel + aspirin) in acute coronary syndrome (ACS) patients with atrial fibrillation (AF), with a similar thrombotic risk. The oral thrombin inhibitor dabigatran (150 mg twice a day) showed superiority over VKA in non‐valvular AF, but data supporting its use in AF patients presenting with ACS are limited.

Objective

We sought to evaluate the efficacy of dabigatran vs. VKA in the management of AF patients undergoing percutaneous coronary intervention for an ACS.

Methods

In this open‐label study, 133 consecutive patients received dabigatran plus clopidogrel. Another cohort of 133 patients treated with VKA plus clopidogrel was used as the control group.

Results

After propensity score adjustment, the cumulative incidence of major adverse cardiovascular events over 24 months was higher with dabigatran vs. VKA (adjusted hazard ratio, 2.28; 95% confidence interval, 1.46–3.56). Similar rates of major bleeding were found (adjusted hazard ratio, 1.17; 95% confidence interval, 0.46–2.96).

Conclusions

In AF patients presenting with ACS, replacement of VKA by dabigatran concurrently with clopidogrel is associated with an increased thrombotic risk, without a reduction in major bleeding.

     

Rivaroxaban reversal with prothrombin complex concentrate or tranexamic acid in healthy volunteers

Essentials

• Specific reversal agents for managing severe factor Xa inhibitor‐associated bleeding are lacking.
• We assessed 4‐factor‐prothrombin complex concentrate (4F‐PCC) and tranexamic acid (TXA).
• 4F‐PCC, but not TXA, reduced the prothrombin time and increased endogenous thrombin potential.
• These agents may be viable options for reversal of therapeutic doses of rivaroxaban.

Summary

Background

Oral activated factor X inhibitors such as rivaroxaban are widely used, but specific reversal agents are lacking. Although four‐factor prothrombin complex concentrate (4F‐PCC) and tranexamic acid (TXA) are sometimes used to manage serious bleeding, their efficacy is unknown. Prior studies in healthy subjects taking rivaroxaban revealed that 4F‐PCC partially reverses the prolonged prothrombin time (PT), and fully restores the endogenous thrombin potential (ETP). The effect of TXA has not been evaluated.

Methods

In this double‐blind, parallel‐group study, 147 healthy volunteers given rivaroxaban 20 mg twice daily for 3 days were randomized after their morning dose on day 4 to receive intravenous 4F‐PCC (50 IU kg^?1), TXA (1.0 g), or saline. Standardized punch biopsies were performed at baseline and after 4F‐PCC, TXA or saline administration. Reversal was assessed by measuring bleeding duration and bleeding volume at biopsy sites, and by determining the PT and ETP.

Results

As compared with saline, 4F‐PCC partially reversed the PT and completely reversed the ETP, whereas TXA had no effect. Neither 4F‐PCC nor TXA reduced bleeding duration or volume. All treatments were well tolerated, with no recorded adverse events.

Conclusions

Although 4F‐PCC reduced the PT and increased the ETP in volunteers given supratherapeutic doses of rivaroxaban, neither 4F‐PCC nor TXA influenced punch biopsy bleeding.

     

Less abnormal uterine bleeding with dabigatran than warfarin in women treated for acute venous thromboembolism

Essentials

• Factor Xa inhibitors cause more abnormal menstrual bleeding (AUB) than vitamin‐K antagonists (VKA).
• We analyzed data of AUB in women, evaluating dabigatran versus VKA.
• We observed a 41% lower risk of AUB in women on dabigatran compared to those on VKA.
• Our findings of lower AUB risk on dabigatran should be corroborated in future studies.

Summary

Introduction

Although direct oral anticoagulants (DOACs) are associated with a better safety profile than warfarin in patients with acute venous thromboembolism (VTE), direct factor Xa inhibitors involve a higher risk of abnormal uterine bleeding (AUB). We aimed to determine the risk of AUB during anticoagulation with dabigatran compared with warfarin.

Methods

Post‐hoc analysis of the pooled RE‐COVER studies and the RE‐MEDY trial. Incidences of AUB, based on a defined preferred terms search for adverse events, in female patients aged 18–50 years treated with dabigatran, were compared with those in women treated with warfarin.

Results

Of the 2964 women included in the above‐mentioned trials, 1280 women were in the relevant age category (18–50 years) and included in the current analysis. A total of 643 patients were randomized to treatment with dabigatran and 637 to treatment with warfarin. The overall rate of AUB was 8.1%, 5.9% for the women treated with dabigatran and 9.6% in those treated with warfarin, for an odds ratio for dabigatran‐treated patients of 0.59 (95% confidence interval [CI], 0.39–0.90; P = 0.015). In the dabigatran‐treated patients, three (0.5%) suffered major bleeding (MB) vs. five (0.8%) in the warfarin‐treated patients (HR, 0.65; 95% CI, 0.15–2.72). MB or non‐major relevant bleeding occurred in 30 (4.7%) patients randomized to receive dabigatran and 57 (8.9%) randomized to receive warfarin (HR, 0.53; 95% CI, 0.34–0.83). None of the bleeding events was fatal.

Conclusion

Dabigatran treatment was associated with a significantly (41%) lower risk of AUB than warfarin. Future studies in daily practice are needed to corroborate these findings.

     

Rivaroxaban for thromboprophylaxis among patients recently hospitalized for acute infectious diseases: a subgroup analysis of the MAGELLAN study

Essentials

• Net benefit of venous thromboprophylaxis (VTE) in patients hospitalized for infections is unknown.
• MAGELLAN trial subgroup analysis was performed for patients hospitalized for acute infectious diseases.
• At day 35, prolonged rivaroxaban prophylaxis reduced VTE compared to enoxaparin (4.2% vs. 6.6%).
• Rivaroxaban prophylaxis reduced VTE in patients hospitalized for active lung infections.

Summary

Background

Despite the well‐established association between infection and venous thromboembolism (VTE), there are few data specifically assessing the efficacy and safety of the VTE prophylaxis strategies for patients hospitalized for acute infectious diseases.

Objectives

To estimate the incidence of VTE and bleeding outcomes, comparing prolonged prophylaxis with rivaroxaban 10 mg daily for 35 days with enoxaparin 40 mg daily for 10 days.

Patients/Methods

A subgroup analysis of patients hospitalized for acute infectious diseases in the MAGELLAN trial was performed. The primary efficacy outcome was the composite of asymptomatic proximal or symptomatic VTE at days 10 and 35. The principal safety outcome was the composite of major or clinically relevant non‐major bleeding.

Results

Three thousand one hundred and seventy‐three patients with acute infectious diseases leading to hospitalization were randomized to either rivaroxaban (n = 1585) or enoxaparin/placebo (n = 1588), and received at least one dose of study medication. At day 10, primary composite efficacy outcomes did not differ between prophylaxis strategies (rivaroxaban, 2.7%; and enoxaparin, 3.7%). At day 35, there were fewer VTE events with rivaroxaban (4.2%) than with enoxaparin (6.6%) (relative risk [RR] 0.64; 95% confidence interval [CI] 0.45–0.92). Patients with pulmonary infections randomized to rivaroxaban had a lower incidence of VTE both at 10 days (RR 0.50, 95% CI 0.28–0.90) and at 35 days (RR 0.54, 95% CI 0.33–0.87). Primary safety outcome events were increased with rivaroxaban (RR 2.42, 95% CI 1.60–3.66).

Conclusions

Prolonged rivaroxaban prophylaxis reduced the incidence of VTE in patients hospitalized for acute infectious diseases, particularly those involving the lungs. Efficacy benefits were, in part, offset by bleeding outcomes. ClinicalTrials.gov Number: NCT 00571649.

     

Genes associated with venous thromboembolism in colorectal cancer patients

Essentials

• The underlying pathophysiological mechanisms behind cancer‐associated thrombosis are unknown.
• We compared expression profiles in tumor cells from patients with and without thrombosis.
• Tumors from patients with thrombosis showed significant differential gene expression profiles.
• Patients with thrombosis had a proinflammatory status and increased fibrin levels in the tumor.

Summary

Background

Venous thromboembolism (VTE) is a frequent complication in patients with cancer, and is associated with significant morbidity and mortality. However, the mechanisms behind cancer‐associated thrombosis are still incompletely understood.

Objectives

To identify novel genes that are associated with VTE in patients with colorectal cancer (CRC).

Methods

Twelve CRC patients with VTE were age‐matched and sex‐matched to 12 CRC patients without VTE. Tumor cells were isolated from surgical samples with laser capture microdissection approaches, and mRNA profiles were measured with next‐generation RNA sequencing.

Results

This approach led to the identification of new genes and pathways that might contribute to VTE in CRC patients. Application of ingenuity pathway analysis indicated significant links with inflammation, the methionine degradation pathway, and increased platelet function, which are all key processes in thrombus formation. Tumor samples of patients with VTE had a proinflammatory status and contained higher levels of fibrin and fibrin degradation products than samples of those without VTE.

Conclusion

This case–control study provides a proof‐of‐principle that tumor gene expression can discriminate between cancer patients with low and high risks of VTE. These findings may help to further unravel the pathogenesis of cancer‐related VTE. The identified genes could potentially be used as candidate biomarkers to select high‐risk CRC patients for thromboprophylaxis.

     

Heparin–protamine balance after neonatal cardiopulmonary bypass surgery

Essentials

• Heparin‐protamine balance (HPB) modulates bleeding after neonatal cardiopulmonary bypass (CPB).
• HPB was examined in 44 neonates undergoing CPB.
• Post‐operative bleeding occurred in 36% and heparin rebound in 73%.
• Thrombin‐initiated fibrin clot kinetic assay and partial thromboplastin time best assessed HPB.

Summary

Background

Neonates undergoing cardiopulmonary bypass (CPB) are at risk of excessive bleeding. Blood is anticoagulated with heparin during CPB. Heparin activity is reversed with protamine at the end of CPB. Paradoxically, protamine also inhibits blood coagulation when it is dosed in excess of heparin.

Objectives

To evaluate heparin–protamine balance in neonates undergoing CPB by using research and clinical assays, and to determine its association with postoperative bleeding.

Patients/Methods

Neonates undergoing CPB in the first 30 days of life were studied. Blood samples were obtained during and after surgery. Heparin–protamine balance was assessed with calibrated automated thrombography, thrombin‐initiated fibrin clot kinetic assay (TFCK), activated partial thromboplastin time (APTT), anti‐FXa activity, and thromboelastometry. Excessive postoperative bleeding was determined by measurement of chest tube output or the development of cardiac tamponade.

Results and Conclusions

Of 44 neonates enrolled, 16 (36%) had excessive postoperative bleeding. The TFCK value was increased. By heparin in neonatal blood samples, but was only minimally altered by excess protamine. Therefore, it reliably measured heparin in samples containing a wide range of heparin and protamine concentrations. The APTT most closely correlated with TFCK results, whereas anti‐FXa and thromboelastometry assays were less correlative. The TFCK and APTT assay also consistently detected postoperative heparin rebound, providing an important continued role for these long‐established coagulation tests in the management of postoperative bleeding in neonates requiring cardiac surgical repair. None of the coagulation tests predicted the neonates who experienced postoperative bleeding, reflecting the multifactorial causes of bleeding in this population.

     

Polymorphism in dural arteriovenous fistula: matrix metalloproteinase‐2‐1306 C/T as a potential risk factor for sinus thrombosis

Essentials

• Sinus thrombosis may play a crucial role in development of dural arteriovenous fistula (DAVF).
• Little is known about the association between gene polymorphism and the development of DAVF.
• MMP‐2‐1306 C/T showed a higher prevalence rate in DAVF cases with sinus thrombosis.
• MMP‐2‐1306C/T polymorphism is likely a potential risk factor for sinus thrombosis in DAVF.

Summary

Background

Dural arteriovenous fistula (DAVF) is a rare but important cerebrovascular disorder in adults. Little is known about the molecular genetic pathogenesis underlying DAVF development.

Objectives

To investigate the associations of gene polymorphisms and DAVF.

Materials and Methods

By the use of real‐time PCR genotyping, seven single‐nucleotide polymorphisms (SNPs) of angiogenesis‐related genes were analyzed in 72 DAVF patients. Pertinent clinical and imaging data were subgrouped on the basis of location (cavernous sinus versus lateral sinus), lesions (single versus multiple), cerebral venous reflux (CVR) grading (Borden I versus Borden II/III), and sinus thrombosis (with versus without).

Results

We found that individuals carrying the polymorphic allele of matrix metalloproteinase (MMP)‐2‐1306 C/T (rs243865) had a significantly increased risk of sinus thrombosis in DAVF (odds ratio 6.2; 95% confidence interval 1.7–22.9). There was a weak difference in associations of tissue inhibitor of metalloproteinase (TIMP)‐2 (rs2277698) gene polymorphism and DAVF patients subgrouped by CVR grading.

Conclusions

These preliminary results indicate that MMP‐2‐1306 C/T, but not MMP‐9, TIMP‐1, TIMP‐2, and vascular endothelial growth factor A SNP variants, is a risk factor for the development of sinus thrombosis in DAVF patients.

     

The perils of inhibiting deficient factors

Essentials

• Anticoagulation in patients with factor X deficiency is an evidence‐poor area.
• A patient with factor X deficiency was anticoagulated with warfarin followed by rivaroxaban.
• Warfarin may be a safer anticoagulant option than rivaroxaban in hereditary factor X deficiency.
• A baseline coagulation screen should be performed prior to commencement of anticoagulation.

Summary

We report a case of a previously undiagnosed factor X deficiency in an 83‐year‐old man who had no previous bleeding history despite multiple hemostatic challenges. He was anticoagulated with warfarin for atrial fibrillation without bleeding complications; however, major hemorrhage occurred soon after a switch to rivaroxaban.

     

von Willebrand factor propeptide to antigen ratio identifies platelet activation and reduced von Willebrand factor survival phenotype in mice

Essentials

• Reduced survival of von Willebrand factor (VWF) in plasma causes type 1C von Willebrand disease.
• Blood was collected from mouse strains by various methods and VWF propeptide and antigen assayed.
• VWF propeptide to antigen ratio identifies a reduced VWF survival phenotype in mice.
• This ratio validates the acceptability of murine blood samples for coagulation studies.

Summary

Background

Reduced plasma survival of von Willebrand factor (VWF) is characteristic of patients with type 1C von Willebrand disease (VWD). These subjects can be identified by an increased steady‐state ratio of plasma VWF propeptide (VWFpp) to VWF antigen (VWF:Ag). A similar phenotype occurs in mice with the Mvwf1 allele.

Objectives

To (i) determine if the VWFpp/VWF:Ag ratio can be used to identify a ‘type 1C’ phenotype in mice, (ii) determine the most reliable method for murine blood sampling, and (iii) identify the source of VWF released during problematic blood collection.

Methods

‘Platelet‐VWF’ and ‘endothelial‐VWF’ mice were generated by bone marrow transplantation between C57BL/6J and VWF‐/‐ mice. Several blood sampling methods were used and murine VWFpp and VWF:Ag levels determined. Plasma and platelet VWF:Ag and VWFpp, VWF multimers and VWF half‐life were examined in mouse strains with and without Mvwf1.

Results

A single retro‐orbital bleed and vena cava collection were found to be the optimal methods of blood collection. Problematic collection resulted in release of VWF from platelets and endothelium. The VWFpp/VWF:Ag ratio identified strains of mice with reduced VWF survival.

Conclusion

Assay of murine VWFpp and VWF:Ag has utility in determining the acceptability of murine blood samples for coagulation testing and in identification of a reduced VWF survival phenotype in mice.

     

Metabolomic analysis of 92 pulmonary embolism patients from a nested case–control study identifies metabolites associated with adverse clinical outcomes

Essentials

• Risk‐stratification often fails to predict clinical deterioration in pulmonary embolism (PE).
• First‐ever high‐throughput metabolomics analysis of risk‐stratified PE patients.
• Changes in circulating metabolites reflect a compromised energy metabolism in PE.
• Metabolites play a key role in the pathophysiology and risk stratification of PE.

Summary

Background

Patients with acute pulmonary embolism (PE) exhibit wide variation in clinical presentation and outcomes. Our understanding of the pathophysiologic mechanisms differentiating low‐risk and high‐risk PE is limited, so current risk‐stratification efforts often fail to predict clinical deterioration and are insufficient to guide management.

Objectives

To improve our understanding of the physiology differentiating low‐risk from high‐risk PE, we conducted the first‐ever high‐throughput metabolomics analysis (843 named metabolites) comparing PE patients across risk strata within a nested case–control study.

Patients/methods

We enrolled 92 patients diagnosed with acute PE and collected plasma within 24 h of PE diagnosis. We used linear regression and pathway analysis to identify metabolites and pathways associated with PE risk‐strata.

Results

When we compared 46 low‐risk with 46 intermediate/high‐risk PEs, 50 metabolites were significantly different after multiple testing correction. These metabolites were enriched in the following pathways: tricarboxylic acid (TCA) cycle, fatty acid metabolism (acyl carnitine) and purine metabolism, (hypo)xanthine/inosine containing. Additionally, energy, nucleotide and amino acid pathways were downregulated in intermediate/high‐risk PE patients. When we compared 28 intermediate‐risk with 18 high‐risk PE patients, 41 metabolites differed at a nominal P‐value level. These metabolites were enriched in fatty acid metabolism (acyl cholines), and hemoglobin and porphyrin metabolism.

Conclusion

Our results suggest that high‐throughput metabolomics can provide insight into the pathophysiology of PE. Specifically, changes in circulating metabolites reflect compromised energy metabolism in intermediate/high‐risk PE patients. These findings demonstrate the important role metabolites play in the pathophysiology of PE and highlight metabolomics as a potential tool for risk stratification of PE.

     

Acute coronary syndrome remodels the antiplatelet aggregation properties of HDL particle subclasses

Essentials

• HDL subclasses were studied in acute coronary syndrome (ACS).
• HDL2 from ACS patients have better antiplatelet potency than HDL from non ACS subjects.
• ACS remodels the antiplatelet properties of HDL subclasses.
• Oxidized polyunsaturated fatty acids content of HDL is modified by ACS.

Summary

Background

Although HDLs have antithrombotic effects by reducing platelet activation, the relationship between HDL levels and the risk of acute coronary syndrome (ACS) is unclear, as HDL particles are heterogeneous in composition and biological properties.

Objective

To characterize the effects of HDL2 and HDL3 subclasses from ACS patients and non‐coronary artery disease (CAD) subjects on platelet activation.

Methods

We measured platelet aggregation and ex vivo thrombus formation, analyzed signaling pathways by flow cytometry, and performed a targeted lipidomics analysis on HDL subclasses.

Results

Analysis of human platelet aggregation in suspension, adhesion on von Willebrand factor and thrombus formation on collagen under arterial shear demonstrated that HDL2 from ACS patients had higher antiplatelet potency than HDL3 from ACS patients and HDL from non‐CAD subjects. HDL binding to scavenger receptor class B type I was essential for this effect. A lipidomics analysis revealed that HDL2 from ACS patients had more oxidized polyunsaturated fatty acids (PUFAs). An inverse correlation between the concentrations of 9‐hydroxyoctadecadienoic acid (9‐HODE), 13‐hydroxyoctadecadienoic acid (13‐HODE), the eicosapentaenoic acid metabolite 18‐hydroxyeicosapentaenoic acid (18‐HEPE) and hydroxyeicosatetraenoic acid isomers in HDL2 and platelet aggregation was observed. This relationship was further demonstrated by the direct inhibitory effects of 18‐HEPE, 9‐HODE, 13‐HODE, 17‐hydroxydocosahexaenoic acid and 14‐hydroxydocosahexaenoic acid on collagen‐related peptide‐induced platelet aggregation, indicating that oxidized PUFAs contribute to the antithrombotic effect of ACS HDL2.

Conclusions

Our data shed new light on the antiplatelet effects of HDL subclasses, and suggest physiological adaptation through the modulation of HDL properties in ACS patients that may limit their platelet‐dependent thrombotic risk.

     

A first‐in‐human study of the safety,tolerability, pharmacokinetics and pharmacodynamics of PF‐06741086, an anti‐tissue factor pathway inhibitor mAb,in healthy volunteers

Essentials

• Tissue factor pathway inhibitor (TFPI) is an antagonist of FXa and the TF‐FVIIa complex.
• PF‐06741086 is an IgG₁ monoclonal antibody that targets the Kunitz‐2 domain of TFPI.
• Single doses of PF‐06741086 were evaluated in a phase 1 study in healthy volunteers.
• Data from this study support further investigation of PF‐06741086 in individuals with hemophilia.

Summary

Background

Tissue factor pathway inhibitor (TFPI) is a protease inhibitor of the tissue factor–activated factor VII complex and activated FX. PF‐06741086 is a mAb that targets TFPI to increase clotting activity.

Objectives

This study was a randomized, double‐blind, sponsor‐open, placebo‐controlled, single intravenous or subcutaneous dose escalation study to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of PF‐06741086.

Patients/Methods

Volunteers who provided written informed consent were assigned to cohorts with escalating dose levels. Safety endpoints included treatment‐emergent adverse events (TEAEs), infusion/injection site reactions, vital signs, electrocardiogram, and coagulation and hematology laboratory parameters. Pharmacokinetic (PK) and pharmacodynamic (PD) endpoints included exposures of PF‐06741086 in plasma and measures of PF‐06741086 pharmacology, respectively.

Results

Forty‐one male volunteers were recruited overall. Thirty‐two were dosed with PF‐06741086 from 30 mg subcutaneously to 440 mg intravenously. All doses were safe and well tolerated. TEAEs were mild or moderate in severity, laboratory abnormalities were transient, there were no serious adverse events, there were no infusion/injection site reactions, and no dose escalation stopping criteria were met. Plasma exposures of PF‐06741086 increased greater than proportionally with dose under the same dosing route. Coagulation pharmacology was demonstrated via total TFPI, dilute prothrombin time, D‐dimer, prothrombin fragment 1 + 2 and thrombin generation assay parameters.

Conclusions

Single doses of PF‐06741086 at multiple dose levels were safe and well tolerated in a healthy adult male population. The safety, PK and PD data from this study support progression to a multiple‐dose study in hemophilic patients.

     

Extended International Normalized Ratio testing intervals for warfarin‐treated patients

Essentials

• Warfarin typically requires International Normalized Ratio (INR) testing at least every 4 weeks.
• We implemented extended INR testing for stable warfarin patients in six anticoagulation clinics.
• Use of extended INR testing increased from 41.8% to 69.3% over the 3 year study.
• Use of extended INR testing appeared safe and effective.

Summary

Background

A previous single‐center randomized trial suggested that patients with stable International Normalized Ratio (INR) values could safely receive INR testing as infrequently as every 12 weeks.

Objective

To test the success of implementation of an extended INR testing interval for stable warfarin patients in a practice‐based, multicenter collaborative of anticoagulation clinics.

Methods

At six anticoagulation clinics, patients were identified as being eligible for extended INR testing on the basis of prior INR value stability and minimal warfarin dose changes between 2014 and 2016. We assessed the frequency with which anticoagulation clinic providers recommended an extended INR testing interval (> 5 weeks) to eligible patients. We also explored safety outcomes for eligible patients, including next INR values, bleeding events, and emergency department visits.

Results

At least one eligible period for extended INR testing was identified in 890 of 3362 (26.5%) warfarin‐treated patients. Overall, the use of extended INR testing in eligible patients increased from 41.8% in the first quarter of 2014 to 69.3% in the fourth quarter of 2016. The number of subsequent out‐of‐range next INR values were similar between eligible patients who did and did not have an extended INR testing interval (27.3% versus 28.4%, respectively). The numbers of major bleeding events were not different between the two groups, but rates of clinically relevant non‐major bleeding (0.02 per 100 patient‐years versus 0.09 per 100 patient‐years) and emergency department visits (0.07 per 100 patient‐years versus 0.19 per 100 patient‐years) were lower for eligible patients with extended INR testing intervals than for those with non‐extended INR testing intervals.

Conclusions

Extended INR testing for stable warfarin patients can be successfully and safely implemented in diverse, practice‐based anticoagulation clinic settings.

     

Sex‐specific performance of pre‐imaging diagnostic algorithms for pulmonary embolism

Essentials

• Decision rules for pulmonary embolism are used indiscriminately despite possible sex‐differences.
• Various pre‐imaging diagnostic algorithms have been investigated in several prospective studies.
• When analysed at an individual patient data level the algorithms perform similarly in both sexes.
• Estrogen use and male sex were associated with a higher prevalence in suspected pulmonary embolism.

Summary

Background

In patients suspected of pulmonary embolism (PE), clinical decision rules are combined with D‐dimer testing to rule out PE, avoiding the need for imaging in those at low risk. Despite sex differences in several aspects of the disease, including its diagnosis, these algorithms are used indiscriminately in women and men.

Objectives

To compare the performance, defined as efficiency and failure rate, of three pre‐imaging diagnostic algorithms for PE between women and men: the Wells rule with fixed or with age‐adjusted D‐dimer cut‐off, and a recently validated algorithm (YEARS). A secondary aim was to determine the sex‐specific prevalence of PE.

Methods

Individual patient data were obtained from six studies using the Wells rule (fixed D‐dimer, n = 5; age adjusted, n = 1) and from one study using the YEARS algorithm. All studies prospectively enrolled consecutive patients with suspected PE. Main outcomes were efficiency (proportion of patients in which the algorithm ruled out PE without imaging) and failure rate (proportion of patients with PE not detected by the algorithm). Outcomes were estimated using (multilevel) logistic regression models.

Results

The main outcomes showed no sex differences in any of the separate algorithms. With all three, the prevalence of PE was lower in women (OR, 0.66, 0.68 and 0.74). In women, estrogen use, adjusted for age, was associated with lower efficiency and higher prevalence and D‐dimer levels.

Conclusions

The investigated pre‐imaging diagnostic algorithms for patients suspected of PE show no sex differences in performance. Male sex and estrogen use are both associated with a higher probability of having the disease.

     

Expression and functional characterization of two natural heparin‐binding site variants of antithrombin

Essentials

• Heparin‐binding site (HBS) variants of antithrombin (AT) are associated with thrombosis risk.
• HSB variants have, in general, normal progressive inhibitory activity but reduced heparin affinity.
• Thrombosis in HSB carriers has been primarily attributed to the loss of heparin cofactor activity.
• Results here demonstrate that HSB variants of AT also lack anti‐inflammatory signaling functions.

Summary

Background

Several heparin‐binding site (HBS) variants of antithrombin (AT) have been identified that predispose carriers to a higher incidence of thrombosis. Thrombosis in carriers of HBS variants has been primarily attributed to a loss in their heparin‐dependent anticoagulant function.

Objective

The objective of this study was to determine whether HSB mutations affect the anti‐inflammatory functions of variants.

Methods

Two HBS variants of AT (AT‐I7N and AT‐L99F), which are known to be associated with a higher incidence of thrombosis, were expressed in mammalian cells and purified to homogeneity. These variants were characterized by kinetic assays followed by analysis of their activities in established cellular and/or in vivo inflammatory models. The possible effects of mutations on AT structure were also evaluated by molecular modeling.

Results

The results indicated that, whereas progressive inhibitory activities of variants were minimally affected, their heparin affinity and inhibitory activity in the presence of heparin were markedly decreased. Unlike wild‐type AT, neither AT variant was capable of inhibiting activation of nuclear factor‐κB or downregulation of expression of cell adhesion molecules in response to lipopolysaccharide (LPS). Similarly, neither variant elicited barrier protective activity in response to LPS. Structural analysis suggested that the L99F substitution locally destabilizes AT structure.

Conclusions

It is concluded that the L99F mutation of AT is associated with destabilization of the serpin structure, and that the loss of anti‐inflammatory signaling function of the HBS variants may also contribute to enhanced thrombosis in carriers of HBS mutations.

     

Mortality due to bleeding,myocardial infarction and stroke in dialysis patients

Essentials

• Mortality due to bleeding vs. arterial thrombosis in dialysis patients is unknown.
• We compared death causes of 201 918 dialysis patients with the general population.
• Dialysis was associated with increased mortality risks of bleeding and arterial thrombosis.
• Clinicians should be aware of the increased bleeding and thrombosis risks.

Summary

Background

Dialysis has been associated with both bleeding and thrombotic events. However, there is limited information on bleeding as a cause of death versus arterial thrombosis as a cause of death.

Objectives

To investigate the occurrence of bleeding, myocardial infarction and stroke as causes of death in the dialysis population as compared with the general population.

Methods

We included 201 918 patients from 11 countries providing data to the ERA‐EDTA Registry who started dialysis treatment between 1994 and 2011, and followed them for 3 years. Age‐standardized and sex‐standardized mortality rate ratios for bleeding, myocardial infarction and stroke as causes of death were calculated in dialysis patients as compared with the European general population. Associations between potential risk factors and these causes of death in dialysis patients were investigated by calculating hazard ratios (HRs) with 95% confidence intervals (CIs) by the use of Cox proportional‐hazards regression.

Results

As compared with the general population, the age‐standardized and sex‐standardized mortality rate ratios in dialysis patients were 12.8 (95% CI 11.9–13.7) for bleeding as a cause of death (6.2 per 1000 person‐years among dialysis patients versus 0.3 per 1000 person‐years in the general population), 13.4 (95% CI 13.0–13.9) for myocardial infarction (22.5 versus 0.9 per 1000 person‐years), and 12.4 (95% CI 11.9–12.9) for stroke (14.3 versus 0.7 per 1000 person‐years).

Conclusion

Dialysis patients have highly increased risks of death caused by bleeding and arterial thrombosis as compared with the general population. Clinicians should be aware of the increased mortality risks caused by these conditions.

     

High and long‐term von Willebrand factor expression after Sleeping Beauty transposon‐mediated gene therapy in a mouse model of severe von Willebrand disease

Essentials

• von Willebrand disease (VWD) is the most common inherited bleeding disorder.
• Gene therapy for VWD offers long‐term therapy for VWD patients.
• Transposons efficiently integrate the large von Willebrand factor (VWF) cDNA in mice.
• Liver‐directed transposons support sustained VWF expression with suboptimal multimerization.

Summary

Background

Type 3 von Willebrand disease (VWD) is characterized by complete absence of von Willebrand factor (VWF). Current therapy is limited to treatment with exogenous VWF/FVIII products, which only provide a short‐term solution. Gene therapy offers the potential for a long‐term treatment for VWD.

Objectives

To develop an integrative Sleeping Beauty (SB) transposon‐mediated VWF gene transfer approach in a preclinical mouse model of severe VWD.

Methods

We established a robust platform for sustained transgene murine VWF (mVWF) expression in the liver of Vwf^?/? mice by combining a liver‐specific promoter with a sandwich transposon design and the SB100X transposase via hydrodynamic gene delivery.

Results

The sandwich SB transposon was suitable to deliver the full‐length mVWF cDNA (8.4 kb) and supported supra‐physiological expression that remained stable for up to 1.5 years after gene transfer. The sandwich vector stayed episomal (~60 weeks) or integrated in the host genome, respectively, in the absence or presence of the transposase. Transgene integration was confirmed using carbon tetrachloride‐induced liver regeneration. Analysis of integration sites by high‐throughput analysis revealed random integration of the sandwich vector. Although the SB vector supported long‐term expression of supra‐physiological VWF levels, the bleeding phenotype was not corrected in all mice. Long‐term expression of VWF by hepatocytes resulted in relatively reduced amounts of high‐molecular‐weight multimers, potentially limiting its hemostatic efficacy.

Conclusions

Although this integrative platform for VWF gene transfer is an important milestone of VWD gene therapy, cell type‐specific targeting is yet to be achieved.

     

Standardization of extracellular vesicle measurements by flow cytometry through vesicle diameter approximation

Essentials

• Platelet extracellular vesicles (EVs) concentrations measured by flow cytometers are incomparable.
• A model is applied to convert ambiguous scatter units to EV diameter in nanometer.
• Most included flow cytometers lack the sensitivity to detect EVs of 600 nm and smaller.
• The model outperforms polystyrene beads for comparability of platelet EV concentrations.

Summary

Background

Detection of extracellular vesicles (EVs) by flow cytometry has poor interlaboratory comparability, owing to differences in flow cytometer (FCM) sensitivity. Previous workshops distributed polystyrene beads to set a scatter‐based diameter gate in order to improve the comparability of EV concentration measurements. However, polystyrene beads provide limited insights into the diameter of detected EVs.

Objectives

To evaluate gates based on the estimated diameter of EVs instead of beads.

Methods

A calibration bead mixture and platelet EV samples were distributed to 33 participants. Beads and a light scattering model were used to set EV diameter gates in order to measure the concentration of CD61–phycoerythrin‐positive platelet EVs.

Results

Of the 46 evaluated FCMs, 21 FCMs detected the 600–1200‐nm EV diameter gate. The 1200–3000‐nm EV diameter gate was detected by 31 FCMs, with a measured EV concentration interlaboratory variability of 81% as compared with 139% with the bead diameter gate. Part of the variation in both approaches is caused by precipitation in some of the provided platelet EV samples. Flow rate calibration proved essential because systems configured to 60 μL min^?1 differed six‐fold in measured flow rates between instruments. Conclusions EV diameter gates improve the interlaboratory variability as compared with previous approaches. Of the evaluated FCMs, 24% could not detect 400‐nm polystyrene beads, and such instruments have limited utility for EV research. Finally, considerable differences were observed in sensitivity between optically similar instruments, indicating that maintenance and training affect the sensitivity.

     

Preoperative platelet transfusions to reverse antiplatelet therapy for urgent non‐cardiac surgery: an observational cohort study

Essentials

• An increasing number of patients requiring surgery receive antiplatelet therapy (APT).
• We analyzed 181 patients receiving presurgery platelet transfusions to reverse APT.
• No coronary thrombosis occurred after platelet transfusion.
• This justifies a prospective trial to test preoperative platelet transfusions to reverse APT.

Summary

Background

Patients receiving antiplatelet therapy (APT) have an increased risk of perioperative bleeding and cardiac adverse events (CAE). Preoperative platelet transfusions may reduce the bleeding risk but may also increase the risk of CAE, particularly coronary thrombosis in patients after recent stent implantation.

Objectives

To analyze the incidence of perioperative CAE and bleeding in patients undergoing non‐cardiac surgery using a standardized management of transfusing two platelet concentrates preoperatively and restart of APT within 24–72 h after surgery.

Methods

A cohort of consecutive patients on APT treated with two platelet concentrates before non‐cardiac surgery between January 2012 and December 2014 was retrospectively identified. Patients were stratified by the risk of major adverse cardiac and cerebrovascular events (MACCE). The primary objective was the incidence of CAE (myocardial infarction, acute heart failure and cardiac troponine T increase). Secondary objectives were incidences of other thromboembolic events, bleedings, transfusions and mortality.

Results

Among 181 patients, 88 received aspirin, 21 clopidogrel and 72 dual APT. MACCE risk was high in 63, moderate in 103 and low in 15 patients; 67 had cardiac stents. Ten patients (5.5%; 95% CI, 3.0–9.9%) developed a CAE (three myocardial infarctions, four cardiac failures and three troponin T increases). None was caused by coronary thrombosis. Surgery‐related bleeding occurred in 22 patients (12.2%; 95% CI, 8.2–17.7%), making 12 re‐interventions necessary (6.6%; 95% CI, 3.8–11.2%).

Conclusion

Preoperative platelet transfusions and early restart of APT allowed urgent surgery and did not cause coronary thromboses, but non‐thrombotic CAEs and re‐bleeding occurred. Randomized trials are warranted to test platelet transfusion against other management strategies.