Oral anticoagulant drugs

The historical origins of modern international normalized ratio targets

Prothrombin time (PT) and its derivative international normalized ratio (INR) are frequently ordered to assess the coagulation system. Plasma transfusion to treat incidentally abnormal PT/INR is a common practice with low biological plausibility and without credible evidence, yet INR targets appear in major clinical guidelines and account for the majority of plasma use at many institutions. In this article, we review the historical origins of INR targets. We recount historical milestones in the development of the PT, discovery of vitamin K antagonists (VKAs), motivation for INR standardization, and justification for INR targets in patients receiving VKA therapy. Next, we summarize evidence for INR testing to assess bleeding risk in patients not on VKA therapy and plasma transfusion for treating mildly abnormal INR to prevent bleeding in these patients. We conclude with a discussion of the parallels in misunderstanding of historic PT and present-day INR testing with lessons from the past that might help rationalize plasma transfusion in the future.

Surface Oxygen Deficiency Enabled Spontaneous Antiprotein Fouling in WO3 Nanosheets for Biosensing in Biological Fluids

Biofouling deteriorates the performance of sensors operated in biofluids. Protein adsorption is believed to be the first step of biofouling, which also reduces biocompatibility by further inducing cell adhesion, platelet activation, and even inflammation. Current studies of antifouling coatings are focused on polymers and hydrogels, which have succeeded in remaining resistant to protein adsorption, but their application on sensor electrodes is limited due to low conductivity and biocompatibility. Here, we report a spontaneous antibiofouling strategy for sensor electrodes by controlling oxygen vacancies in WO3 nanosheets. Irreversible adsorption of proteins was reduced by 76% in unprocessed human plasma when electrodes were coated with WO3 rich in surface oxygen vacancy. These electrodes maintained 91% of the initial current density after 1 month of incubation in human plasma.

A regional anticoagulation program improves safety and outcomes for both children and adults

BACKGROUND

Evidence-based anticoagulation programs usually serve a local, adult patient population. Here we report outcomes for a regional combined pediatric-adult program.

AIMS

The aims of this study were: (1) Compare the pre- vs. post-implementation quality of therapy (% time in therapeutic range (%TTR) and compliance). (2) Assess anticoagulant-relevant outcomes (bleeding and thrombotic complications).

METHODS

Data were collected for the years 2014-2019. Rosendaal linear interpolation was used to calculate %TTR. Bleeding complications were categorized using ISTH-SSC standard nomenclature and new thrombotic events were reviewed.

RESULTS

The patients were divided into a long-term warfarin group (N = 308), 80.2% of whom had cardiac-related therapeutic indications (median age 24y), and a second group (N = 114) comprised of short-term and non-warfarin long-term anticoagulation (median age 16y). Median %TTR for those on long-term warfarin was 78.9%. The incidence of major and clinically relevant non-major bleeding events was 1.65 and 2.43 /100 person-years of warfarin use, respectively. Thromboembolism (TE) incidence was 0.78/100 patient-years of warfarin use. Neither bleeding nor thrombosis was associated with %TTR (p = 0.48). Anticoagulant indication was the only variable associated with bleeding risk (p = 0.005). The second group had no on-therapy TE events but 7.9% experienced bleeding. Complete data were available for a randomly sampled pre-program warfarin group (N = 26). Median %TTR improved from 17.5 to 87% pre- vs. post-implementation. Similarly, compliance (defined as ≥ 1 INR/month) improved by 34.3%.

CONCLUSIONS

In conclusion, this program significantly improved and sustained %TTR and compliance. The lack of association between bleeding and thrombosis events and %TTR may be related to the high median %TTR (> 70%) achieved by this approach.

Vitamin K antagonists but not non-vitamin K antagonists in addition on antiplatelet therapy should be associated with increase of hematoma volume and mortality in patients with intracerebral hemorrhage: A sub-analysis of PASTA registry study

BACKGROUND AND PURPOSE

Prior concomitant use of vitamin K antagonists (VKAs) and antiplatelet (AP) therapy increase the hematoma volume and mortality compared with VKA monotherapy in patients with intracranial hemorrhage (ICH). However, the prior concomitant use of non-vitamin K oral antagonists (NOACs) and AP has not been clarified.

METHODS

We conducted a PASTA registry study, which was an observational, multicenter, registry of 1043 patients with stroke receiving oral anticoagulants (OACs) in Japan. In the present study, ICH from the PASTA registry was used to analyze the clinical characteristics including mortality among the four groups (NOAC, VKA, NOAC and AP, and VKA and AP) using univariate and multivariate analyses.

RESULTS

Among the 216 patients with ICH, 118 (54.6%), 27 (12.5%), 55 (25.5%), 16 (7.4%) were taking NOAC monotherapy, NOAC and AP, VKA, and VKA and AP, respectively. In-hospital mortality rates were the highest in VKA and AP (31.3%) than in NOACs (11.9%), NOACs and AP (7.4%), and VKA (7.3%). Multivariate logistic regression analysis demonstrated that the concomitant use of VKA and AP (odds ratio [OR], 20.57; 95% confidence interval [CI], 1.75-241.75, p = 0.0162), initial National Institutes of Health Stroke Scale score (OR, 1.21; 95%CI, 1.10-1.37, p < 0.0001), hematoma volume (OR, 1.41; 95%CI, 1.10-1.90, p = 0.066), and systolic blood pressure (OR, 1.31; 95%CI, 1.00-1.75, p = 0.0422) were independently associated with in-hospital mortality.

CONCLUSIONS

Although VKA in addition to AP therapy could increase the in-hospital mortality, NOAC and AP did not increase the hematoma volume, stroke severity, or mortality compared to NOAC monotherapy.

Prevalence and factors associated with psychological distress among patients on warfarin at the Uganda Heart Institute, Mulago Hospital

INTRODUCTION

Cardiovascular diseases (CVD) are the leading cause of mortality worldwide and are significantly associated with multiple comorbid disorders including mental disorders such as psychological distress (PD). At increased risk of PD are CVD patient sub-categories that not only require chronic therapy but also need follow up with continuous blood tests and dose adjustments (like the patients on warfarin). However, not much has been done to ascertain the burden of PD among patients on warfarin in Uganda.

OBJECTIVE

To determine the prevalence and factors associated with PD among patients on anticoagulation with warfarin at the Uganda Heart Institute (UHI).

METHODS

In this analytical cross-sectional study, 197 participants were sampled from adults on warfarin attending the Uganda Heart Institute (UHI) out patient clinic. The Self Reporting Questionnaire (SRQ-20), a tool with a total maximum score of 20 and cutoff for PD at ≥6 was used to determine the presence of PD among participants, and a socio-demographic questionnaire to document the socio-demographic characteristics of the subjects. Additional questions including the underlying CVD diagnosis, medications used (besides warfarin) and presence of chronic illnesess were also assessed. Bi-variable and multi-variabe logistic regression analysis techniques were used to examine the associations between the dependent and independent variables.

RESULTS

The prevalence of PD was 32%. The unemployed participants were 4.5 times more likely to have PD (adjusted odds ratio [aOR]4.56, 95% confidence interval [CI]: 1.12-18.62, p = 0.04). Participants who had experienced social stressors were more likely to have PD (aOR: 11.38, CI: 3.60-36.04, p < 0.01). Other factors associated with a higher likelihood of having PD included: presence of other chronic comorbidities (aOR: 3.69, CI: 1.24-11.02, p = 0.02) and concomitant use of loop diuretics (aOR: 4.13, CI: 1.67-10.19,p < 0.01). A shorter length of time on warfarin (7-24 months) lowered the likelihood of PD (aOR: 0.23, CI: 0.07-0.74, p = 0.01).

CONCLUSION

The prevalence of PD was high among patients on warfarin in this low income setting and there is a need to characterize the specific psychiatric disorders in patients with CVD. Interventions that address the high burden of PD are urgently needed in this setting.

Eighty years of oral anticoagulation: Learning from history

In the year 2021 we celebrate the 80th anniversary of the first clinical use of vitamin K antagonists (VKAs), the mainstay of prevention and long-term treatment of thromboembolic disease. The discovery and development of oral anticoagulants is one of the most important chapters in the history of medicine, a goal pursued by physicians trying to combat the clinical manifestations of thrombosis since ancient times. Until the last decade, VKAs were the only oral anticoagulants available and used in clinical practice. Today, their clinical use has progressively shrunk, as the non-vitamin K antagonist oral anticoagulants (NOACs) are increasingly replacing VKAs in various conditions after the successful completion of several large randomized controlled trials. Currently, new research is tackling upstream components of the intrinsic pathway - particularly factor XI and factor XII - for the development of new, even safer anticoagulants promising to reduce bleeding without compromising efficacy. This review highlights the evolution of oral anticoagulant therapy tracing the key stages of a long and fascinating history that has unfolded from the first part of the twentieth century until today, indeed an intriguing journey where serendipity is intertwined with the tenacious work of many researchers.

Assessment of the attitude, awareness and practice of periprocedural warfarin management among health care professional in Qatar. A cross sectional survey

It is estimated that 10-15% of oral anticoagulant (OAC) patients, would need to hold their OAC for scheduled surgery. Especially for warfarin, this process is complex and requires multi-layer risk assessment and decisions across different specialties. Clinical guidelines deliver broad recommendations in the area of warfarin management before surgery which can lead to different trends and practices among practitioners. To evaluate the current attitude, awareness, and practice among health care providers (HCPs) on warfarin periprocedural management. A multiple-choice questionnaire was developed, containing questions on demographics and professional information and was completed by187 HCPs involved in warfarin periprocedural management. The awareness median (IQR) score was moderate [64.28% (21.43)]. The level of awareness was associated with the practitioner's specialty and degree of education (P = 0.009, 0.011 respectively). Practice leans to overestimate the need for warfarin discontinuation as well as the need for bridging. Participants expressed interest in using genetic tests to guide periprocedural warfarin management [median (IQR) score (out of 10) = 7 (5)]. In conclusion, the survey presented a wide variation in the clinical practice of warfarin periprocedural management. This study highlights that HCPs in Qatar have moderate awareness. We suggest tailoring an educational campaign or courses towards the identified gaps.

Factor IX p.A37V mutation causes severe bleeding in a patient with phenprocoumon therapy

Background

Bleeding is the most common complication of oral anticoagulants, due to inadequate dosing.

Case presentation

This report describes the clinical course of a patient who developed severe bleeding under therapy with phenprocoumon, despite an INR in the lower therapeutic range. Strikingly, aPTT was prolonged, while factor IX activity was significantly reduced. Acquired hemophilia was excluded, due to missing detection of inhibitors. Finally, sequencing part of the factor IX gene including nucleotide position c.110 revealed a hemizygous factor IX mutation c.110C > T p (Ala37Val).

Conclusions

In rare cases, missense mutations in factor IX propeptide are associated with severe bleeding complications. The substitution of alanin at position 37 to either valin or threonin (Ala37Val or Ala37Thr) leads to hypersensitivity to vitamin k antagonists.

Bridging vs Non-Bridging with Warfarin Peri-Procedural Management: Cost and Cost-Effectiveness Analyses

The warfarin peri-procedural management in Qatar is predominantly based on bridging (63%), compared to non-bridging. This study sought to perform a first-time cost analysis of current warfarin peri-procedural management practices, including a cost-effectiveness analysis (CEA) of predominant bridging vs predominant non-bridging practices. From the hospital perspective, a one-year decision-analytic model followed the cost and success consequences of the peri-procedural warfarin in a hypothetical cohort of 10,000 atrial fibrillation patients. Success was defined as survival with no adverse events. Outcome measures were the cost and success consequences of the 63% bridging (vs not-bridging) practice in the study setting, ie, Hamad Medical Corporation, Qatar, and the incremental cost-effectiveness ratio (ICER, cost/success) of the warfarin therapy when predominantly bridging based vs when predominantly non-bridging based. The model was based on Monte Carlo simulation, and sensitivity analyses were performed to confirm the robustness of the study conclusions. As per 63% bridging practices, the mean overall cost of peri-procedural warfarin management per patient was USD 3,260 (QAR 11,900), associated with an overall success rate of 0.752. Based on the CEA, predominant bridging was dominant (lower cost, higher effect) over the predominant non-bridging practice in 62.2% of simulated cases, with a cost-saving of up to USD 2,001 (QAR 7,303) at an average of USD 272 (QAR 993) and was cost-effective in 36.9% of cases. Being between cost-saving and cost-effective, compared to predominant non-bridging practices, the predominant use of bridging with warfarin seems to be a favorable strategy in atrial fibrillation patients.

Matrix Gla protein maintains normal and malignant hematopoietic progenitor cells by interacting with bone morphogenetic protein-4

Matrix Gla protein (MGP), a modulator of the BMP-SMAD signals, inhibits arterial calcification in a Glu γ-carboxylation dependent manner but the role of MGP highly expressed in a subset of bone marrow (BM) mesenchymal stem/stromal cells is unknown. Here we provide evidence that MGP might be a niche factor for both normal and malignant myelopoiesis. When mouse BM hematopoietic cells were cocultured with mitomycin C-treated BM stromal cells in the presence of anti-MGP antibody, growth of hematopoietic cells was reduced by half, and maintenance of long-term culture-initiating cells (LTC-ICs) was profoundly attenuated. Antibody-mediated blockage of MGP also inhibited growth (by a fifth) and cobblestone formation (by half) of stroma-dependent MB-1 myeloblastoma cells. MGP was undetectable in normal hematopoietic cells but was expressed in various mesenchymal cells and was aberrantly high in MB-1 cells. MGP and bone morphogenetic protein (BMP)-4 were co-induced in stromal cells cocultured with both normal hematopoietic cells and MB-1 myeloblastoma cells in an oscillating several days-periodic manner. BMP-2 was also induced in stromal cells cocultured with normal hematopoietic cells but was barely expressed when cocultured with MB-1 cells. GST-pulldown and luciferase reporter assays showed that uncarboxylated MGP interacted with BMP-4 and that anti-MGP antibody abolished this interaction. LDN-193189, a selective BMP signaling inhibitor, inhibited growth and cobblestone formation of MB-1 cells. The addition of warfarin, a selective inhibitor of vitamin K-dependent Glu γ-carboxylation, did not affect MB-1 cell growth, suggesting that uncarboxylated MGP has a biological effect in niche. These results indicate that MGP may maintain normal and malignant hematopoietic progenitor cells, possibly by modulating BMP signals independently of Glu γ-carboxylation. Aberrant MGP by leukemic cells and selective induction of BMP-4 relative to BMP-2 in stromal cells might specify malignant niche.

How Did We Get Here?: A Historical Review and Critical Analysis of Anticoagulation Therapy Following Mechanical Valve Replacement

Managing severe valvular heart disease with mechanical valve replacement necessitates lifelong anticoagulation with a vitamin K antagonist. Optimal anticoagulation intensity for patients with mechanical valves remains uncertain; current recommendations are inconsistent across guideline bodies and largely based on expert opinion. In this review, we outline the history of anticoagulation therapy in patients with mechanical heart valves and critically evaluate current antithrombotic guidelines for these patients. We conclude that randomized trials evaluating optimal anticoagulation intensity in patients with mechanical valves are needed, and that future guidelines must better justify antithrombotic treatment recommendations.

The blood compatibility challenge. Part 1: Blood-contacting medical devices: The scope of the problem

Blood-contacting medical devices are an integral part of modern medicine. Such devices may be used for only a few hours or may be implanted for life. Despite advances in biomaterial science, clotting on medical devices remains a common problem. Systemic administration of antiplatelet drugs or anticoagulants is often needed to reduce the risk of clotting. Although effective, such therapy increases the risk of bleeding, which can be fatal. This chapter (a) describes some of the commonly used blood-contacting devices and their potential complications, (b) provides an overview of the mechanisms that drive device-associated clotting, and (c) reviews the strategies employed to attenuate clotting on blood-contacting medical devices. STATEMENT OF SIGNIFICANCE: This paper is part 1 of a series of 4 reviews discussing the problem of biomaterial associated thrombogenicity. The objective was to highlight features of broad agreement and provide commentary on those aspects of the problem that were subject to dispute. We hope that future investigators will update these reviews as new scholarship resolves the uncertainties of today.

Genetically Encoded, Functional Single-Strand RNA Origami: Anticoagulant

Nucleic acid aptamers selected for thrombin binding have been previously shown to possess anticoagulant activity; however, problems with rapid renal clearance and short circulation half-life have prevented translation to clinical usefulness. Here, a family of self-folding, functional RNA origami molecules bearing multiple thrombin-binding RNA aptamers and showing significantly improved anticoagulant activity is described. These constructs may overcome earlier problems preventing clinical use of nucleic acid anticoagulants. RNA origami structures are designed in silico and produced by in vitro transcription from DNA templates. Incorporation of 2'-fluoro-modified C- and U-nucleotides is shown to increase nuclease resistance and stability during long-term storage. Specific binding to human thrombin as well as high stability in the presence of RNase A and in human plasma, comparatively more stable than DNA is demonstrated. The RNA origami constructs show anticoagulant activity sevenfold greater than free aptamer and higher than previous DNA weave tiles decorated with DNA aptamers. Anticoagulation activity is maintained after at least 3 months of storage in buffer at 4 °C. Additionally, inhibition of thrombin is shown to be reversed by addition of single-stranded DNA antidotes. This project paves the way for development of RNA origami for potential therapeutic applications especially as a safer surgical anticoagulant.

Use of oral anticoagulant drugs is associated with carotid intraplaque hemorrhage in atherosclerosis patients: a meta-analysis

Patients with carotid atherosclerosis, especially the elderly population, take antithrombotic medicine regularly. However, no previous meta-analysis has focused on one of the possible side effects of such drugs, namely intraplaque hemorrhage (IPH). To determine whether antiplatelet drugs or anticoagulants are associated with an increased risk of carotid IPH. We searched Pubmed, Embase, Ovid MEDLINE, Cochrane Library for relevant studies that were published in English, from January 1st, 1989 to January 1st, 2019. We pooled the odds ratio (OR) with 95% confidence interval (CI) from individual studies and conducted quality assessment, heterogeneity, publication bias analysis and sensitivity analysis. A total of four cross-sectional studies, involving 2714 participants with carotid atherosclerotic plaques was included into this meta-analysis. We found a significant association between the use of anticoagulants and higher risk of carotid IPH (OR 1.95; 95% CI 1.16-3.30, P = 0.92; I² = 0). No significant association was found between the use of antiplatelet drugs and increased risk of carotid IPH (OR 1.34; 95% CI 0.68-2.61, P = 0.03; I² = 65%). Our meta-analysis reveals that it is the use of oral anticoagulants rather than antiplatelet drugs that may be associated with an increased risk of carotid IPH in atherosclerosis patients.

Clinical Pharmacokinetics of Sacubitril/Valsartan (LCZ696): A Novel Angiotensin Receptor-Neprilysin Inhibitor

Sacubitril/valsartan (LCZ696) is indicated for the treatment of heart failure with reduced ejection fraction. Absorption of sacubitril/valsartan and conversion of sacubitril (prodrug) to sacubitrilat (neprilysin inhibitor) was rapid with maximum plasma concentrations of sacubitril, sacubitrilat, and valsartan (angiotensin receptor blocker) reaching within 0.5, 1.5-2.0, and 2.0-3.0 h, respectively. With a two-fold increase in dose, an increase in the area under the plasma concentration-time curve was proportional for sacubitril, ~1.9-fold for sacubitrilat, and ~1.7-fold for valsartan in healthy subjects. Following multiple twice-daily administration, steady-state maximum plasma concentration was reached within 3 days, showing no accumulation for sacubitril and valsartan, while ~1.6-fold accumulation for sacubitrilat. Sacubitril is eliminated predominantly as sacubitrilat through the kidney; valsartan is eliminated mainly by biliary route. Drug-drug interactions of sacubitril/valsartan were evaluated with medications commonly used in patients with heart failure including furosemide, warfarin, digoxin, carvedilol, levonorgestrel/ethinyl estradiol combination, amlodipine, omeprazole, hydrochlorothiazide, intravenous nitrates, metformin, statins, and sildenafil. Co-administration with sacubitril/valsartan increased the maximum plasma concentration (~2.0-fold) and area under the plasma concentration-time curve (1.3-fold) of atorvastatin; however, it did not affect the pharmacokinetics of simvastatin. Age, sex, or ethnicity did not affect the pharmacokinetics of sacubitril/valsartan. In patients with heart failure vs. healthy subjects, area under the plasma concentration-time curves of sacubitril, sacubitrilat, and valsartan were higher by approximately 1.6-, 2.1-, and 2.3-fold, respectively. Renal impairment had no significant impact on sacubitril and valsartan area under the plasma concentration-time curves, while the area under the plasma concentration-time curve of sacubitrilat correlated with degree of renal function (1.3-, 2.3-, 2.9-, and 3.3-fold with mild, moderate, and severe renal impairment, and end-stage renal disease, respectively). Moderate hepatic impairment increased the area under the plasma concentration-time curves of valsartan and sacubitrilat ~2.1-fold.

Mitral valve repair in dogs using an ePTFE chordal implantation device: a pilot study

OBJECTIVE

Mitral valve (MV) regurgitation due to degenerative MV disease is the leading cause of cardiac death in dogs. We carried out preliminary experiments to determine the feasibility and short-term effects of beating-heart MV repair using an expanded polytetrafluorethylene (ePTFE) chordal implantation device (Harpoon TSD-5) in dogs.

ANIMALS

This study involved six healthy purpose-bred Beagles (weight range 8.9-11.4 kg).

MATERIAL AND METHODS

Following a mini-thoracotomy performed under general anesthesia, the TSD-5 was used to place 1 or 2 artificial ePTFE cords on the anterior MV leaflet or the posterior MV leaflet via a left-ventricular transapical approach. The procedure was guided and monitored by transesophageal echocardiography. Postoperative antithrombotic treatment consisted of clopidogrel or a combination of clopidogrel and apixaban. Dogs were serially evaluated by transthoracic echocardiography at day 1, 7, 14, 21, and 30. The hearts were then examined for evaluation of tissues reactions and to detect signs of endothelialization.

RESULTS

One or two chords were successfully implanted in five dogs. Four dogs completed the 30 days follow-up. One dog died intra-operatively because of aortic perforation. One dog died early post-operatively from a hemorrhagic pleural effusion attributed to overly aggressive antithrombotic treatment. One dog developed a thrombus surrounding both the knot and the synthetic cord. Postmortem exam confirmed secure placement of ePTFE knots in the mitral leaflets in all dogs and the presence of endothelialization of the knots and chords.

CONCLUSIONS

These preliminary results demonstrate the feasibility of artificial chordal placement using an ePTFE cordal implantation device in dogs.

Erratum to: Clinical Pharmacokinetics of Sacubitril/Valsartan (LCZ696): A Novel Angiotensin Receptor-Neprilysin Inhibitor

Sacubitril/valsartan (LCZ696) is indicated for the treatment of heart failure with reduced ejection fraction. Absorption of sacubitril/valsartan and conversion of sacubitril (prodrug) to sacubitrilat (neprilysin inhibitor) was rapid with maximum plasma concentrations of sacubitril, sacubitrilat, and valsartan (angiotensin receptor blocker) reaching within 0.5, 1.5-2.0, and 2.0-3.0 h, respectively. With a twofold increase in dose, an increase in the area under the plasma concentration-time curve was proportional for sacubitril, ~1.9-fold for sacubitrilat, and ~1.7-fold for valsartan in healthy subjects. Following multiple twice-daily administration, steady-state maximum plasma concentration was reached within 3 days, showing no accumulation for sacubitril and valsartan, while ~1.6-fold accumulation for sacubitrilat. Sacubitril is eliminated predominantly as sacubitrilat through the kidney; valsartan is eliminated mainly by biliary route. Drug-drug interactions of sacubitril/valsartan were evaluated with medications commonly used in patients with heart failure including furosemide, warfarin, digoxin, carvedilol, levonorgestrel/ethinyl estradiol combination, amlodipine, omeprazole, hydrochlorothiazide, intravenous nitrates, metformin, statins, and sildenafil. Co-administration with sacubitril/valsartan increased the maximum plasma concentration (~2.0-fold) and area under the plasma concentration-time curve (1.3-fold) of atorvastatin; however, it did not affect the pharmacokinetics of simvastatin. Age, sex, or ethnicity did not affect the pharmacokinetics of sacubitril/valsartan. In patients with heart failure vs. healthy subjects, area under the plasma concentration-time curves of sacubitril, sacubitrilat, and valsartan were higher by approximately 1.6-, 2.1-, and 2.3-fold, respectively. Renal impairment had no significant impact on sacubitril and valsartan area under the plasma concentration-time curves, while the area under the plasma concentration-time curve of sacubitrilat correlated with degree of renal function (1.3-, 2.3-, 2.9-, and 3.3-fold with mild, moderate, and severe renal impairment, and end-stage renal disease, respectively). Moderate hepatic impairment increased the area under the plasma concentration-time curves of valsartan and sacubitrilat ~2.1-fold.

Selection and characterization of a DNA aptamer inhibiting coagulation factor XIa

Factor XIa (FXIa) is a serine protease that catalyzes the activation of Factor IX (FIX) in the blood coagulation cascade. FXIa and its precursor FXI are emergent therapeutic targets for the development of safer anticoagulant agents. Here, we sought a novel DNA-based agent to inhibit FXIa. Towards this goal, an 80 base, single-stranded DNA aptamer library (containing a 40 base randomized core) was screened for FXIa-binding candidates, using ten rounds of positive and negative selection. After selection, 6 of 89 different sequences inhibited FXIa-mediated chromogenic substrate S2366 cleavage. The most active anti-FXIa aptamer had a hypervariable central sequence 5′-AACCTATCGGACTATTGTTAGTGATTTTTATAGTGT-3′ and was designated Factor ELeven Inhibitory APtamer (FELIAP). FELIAP, but not a scrambled aptamer control (SCRAPT), competitively inhibited FXIa-catalyzed S2366 cleavage, FIX activation, and complex formation with antithrombin. No effect of FELIAP on FXI activation was observed. FELIAP inhibited plasma clotting and thrombin generation assays to a significantly greater extent than SCRAPT. Immobilized FELIAP bound FXIa with strong affinity and an equilibrium binding constant (K_D) in the low nanomolar range determined using surface plasmon resonance. FELIAP is the first FXIa-inhibitory aptamer to be described and constitutes a lead compound to develop related aptamers for in vivo use.

Pharmacological update: New drugs in cardiac practice: A critical appraisal

Cardiac practice involves the application of a range of pharmacological therapies. An anesthesiologist needs to keep pace with the rampant drug developments in the field of cardiovascular medicine for appropriate management in both perioperative and intensive care set-up, to strengthen his/her role as a perioperative physician in practice. The article reviews the changing trends and the future perspectives in major classes of cardiovascular medicine.

Anticoagulation Monitoring Part 1: Warfarin and Parenteral Direct Thrombin Inhibitors

OBJECTIVE:

To review the availability, mechanisms, limitations, and clinical application of point-of-care (POC) devices used in the management of warfarin and parenteral direct thrombin inhibitors.

DATA SOURCES:

Scientific articles were identified through a MEDLINE search (1966–August 2004), manufacturer Web sites, additional references listed in articles and Web sites, and abstracts from scientific meetings.

STUDY SELECTION AND DATA EXTRACTION:

English-language literature from clinical trials was reviewed to evaluate the accuracy, reliability, and clinical application of POC monitoring devices.

DATA SYNTHESIS:

The prothrombin time expressed as the international normalized ratio (PT—INR) is a well-established test for monitoring warfarin anticoagulation. Multiple devices are available for POC testing. Because there is no universally accepted standard, the performance of each device is typically tested against a standard test performed in a reference laboratory. Performance of currently available devices, as measured by correlations to a standard reference laboratory PT—INR, may be considered very good and acceptable for use in patient care. Utilization of patient self-testing and patient self-monitoring of warfarin anticoagulation using POC devices is increasing. Parenteral direct thrombin inhibitors are typically monitored using a standard laboratory activated partial thromboplastin time. Some research has shown that POC monitoring of direct thrombin inhibitors using the ecarin clotting time is helpful for patients undergoing cardiopulmonary bypass surgery, although that test is not readily available.

CONCLUSIONS:

POC testing for anticoagulation therapy has been available for >20 years. Multiple POC devices are available to monitor warfarin. There is some variability in results between devices and between reagents used in the same device. Despite these limitations, POC monitoring of warfarin via the PT—INR is an integral part of clinical practice. Additional research evaluating POC monitoring of direct thrombin inhibitors is necessary.

Synthesis of nanoparticles based on PDMMLA derivative copolymers and study of warfarin encapsulation and controlled release

The warfarin encapsulation by new biodegradable nanoparticles based on PDMMLA and its controlled release were studied for the first time.

Nontraumatic Retroperitoneal Hematoma After Warfarin Administration: Fatal Case Report and Review of the Literature

Spontaneous retroperitoneal hematoma after warfarin therapy is an extremely rare event. Here, we report a 25-year-old man who was brought in to the emergency service with confusion. On arrival, the patient had hypotension, tachycardia, tachypnea, low-grade fever, and Glasgow Coma Scale score of 12. Abdominal examination revealed distention and mild tenderness in the right upper quadrant of the abdomen. The patient had a history of aortic valve replacement surgery and was on warfarin treatment at an international normalized ratio of 2.4. Our patient progressed to cardiorespiratory arrest. The resuscitation was initiated promptly. Despite all resuscitation measures, including transfusion and administration of high doses of catecholamine, the patient died of hypovolemic shock 3 hours after admission. At autopsy, the external surface of the abdominal great vessels (descending aorta and mesenteric vessels) showed scattered petechial hemorrhages without any visible site of perforation. After comprehensive exploration of the abdomen, no evidence of traumatic event was identified and the cause of internal blood loss was noted as warfarin adverse effect.

Evaluation of Anticoagulation Therapy in an Academic Nursing Home

Objective:

To evaluate the warfarin management patterns in an academic nursing home and evaluate what predetermined factors are associated with variability in the international normalized ratio (INR).

Setting:

A 566-bed academic nursing home.

Methods:

A retrospective chart review of all residents receiving warfarin therapy for >3 consecutive months in a calendar year was conducted. Data were collected regarding the number of times the INR fluctuated during the follow-up period and the degree of fluctuation between each blood sampling. An INR that changed by 0.5–0.99 between samplings was classified as a small fluctuation; a change >0.99 was defined as a large fluctuation. The sample was divided into 2 groups, easy management and difficult management, based on variability in the INR. The easy-management group consisted of residents who had small fluctuations in the INR and who had INRs outside of the therapeutic range ≤10% of the time. The difficult- management group had large fluctuations in the INR, with the ratio outside of the therapeutic range >10% of the time.

Results:

Thirty-seven patients were taking warfarin (mean ± SD age 71 ± 14 y; mean number of medical illnesses 7.6 ± 3). The mean length of time of warfarin therapy was 10.6 ± 3.2 months. The average dose and INR were 4.0 ± 1.9 mg and 2.0 ± 0.3, respectively. No statistically significant differences were found between age, dose, or INR. For patients who had INR values exceeding the therapeutic range, there was no significant difference between the management groups in length of treatment, age, number of medical illnesses, number of high-risk factors, dose, average monthly INR, number of medication adjustments per year, albumin and creatinine levels, total number of medications, or number of routine medications known to interact with warfarin. The difficult-management group received more medications known to interact with warfarin than the easy-management group. These medications may have caused the INR to increase above the normal range (p = 0.003), as well as producing a large (p = 0.001) or small fluctuation (p = 0.0007) in the INR. Of all the interacting medications, 55% were antibiotics and 28% were analgesics. No statistically significant differences in outcome were seen between groups.

Conclusions:

Results of this study indicate that large variations (>0.99) in the INR may be due to newly prescribed medications that enhance the anticoagulant effect of warfarin. These variations may be minimized by closely monitoring the INR when a drug known to interact with warfarin is prescribed.

Subdural Hematoma Due to Probable Warfarin–Fluorouracil Interaction

Objective:

To describe the occurrence of a subdural hematoma in a woman undergoing chemotherapy with cyclophosphamide, methotrexate, and fluorouracil combined with warfarin therapy.

Case Summary:

A 60-year-old white woman with atrial fibrillation underwent radical mastectomy for primary breast cancer with histologically positive axillary lymph nodes. Following surgery, the patient received adjuvant chemotherapy with a CMF 1–8 regimen consisting of cyclophosphamide 100 mg/m2 orally on days 1–14, methotrexate 40 mg/m2 intravenously, and fluorouracil 600 mg/m2 by intravenous bolus on days 1 and 8 every 4 weeks. Warfarin 5 mg/day was administered concomitantly due to atrial fibrillation. Following the second course of concomitant therapy, the patient developed a headache, hemiparesis, and an international normalized ratio (INR) of 7.6, which was highly suggestive of a drug interaction between fluorouracil and warfarin. A computed tomography scan of the brain revealed a left parieto-occipital subdural hematoma.

Discussion:

This case emphasizes the importance of the potentially fatal drug interaction involving warfarin and fluorouracil.

Conclusions:

Several adverse interactions between warfarin and fluorouracil have been reported. Considering the severity of this interaction, close monitoring of the INR is recommended in patients receiving these agents concomitantly.

Outcome Analysis for Treatment in 100 Patients with Deep Vein Thrombosis

The treatment of acute deep vein thrombosis has been the subject of much research aimed at delineat ing the safest and most effective approach to diagnosis and treatment. Studies regarding long-term treatment have been limited by the narrow scope of laboratory and clinical analyses of many patients. In this study of 100 patients with a history of deep vein thrombosis, treated on an outpatient basis by a diverse group of clinicians, follow-up data were retrieved in order to determine the outcomes of various approaches to acute and long-term care. Among individuals followed for > 1 year, in only two patients (2%) was death attributable to a thrombotic event related to the etiology of the first episode of deep vein thrombosis. Most deceased patients succumbed to unrelated causes (11%). Among the 77 survivors, most (52%) received long-term antiplatelet therapy. All individ uals with a plasma coagulation defect, whether inherited or acquired, received anticoagulation with either heparin or warfarin. Since the long-term clinical outcome of most patients with deep vein thrombosis is dependent upon the underlying factor predisposing to thrombosis, the most important treatment decision is to select the therapy most likely to provide benefit without causing hemorrhage. An tiplatelet therapy, heparin, or warfarin may be chosen as appropriate for the individual patient.

Budget Impact of Increasing Market Share of Patient Self-Testing and Patient Self-Management in Anticoagulation

BACKGROUND

Patient self-testing (PST) and/or patient self-management (PSM) might provide better coagulation care than monitoring at specialized anticoagulation centers. Yet, it remains an underused strategy in the Netherlands.

METHODS

Budget-impact analyses of current and new market-share scenarios of PST and/or PSM compared with monitoring at specialized centers were performed for a national cohort of 260,338 patients requiring long-term anticoagulation testing. A health care payer perspective and 1- to 5-year time horizons were applied. The occurrence of thromboembolic and hemorrhagic complications in the aforementioned patient population was assessed in a Markov model. Dutch-specific costs were applied, next to effectiveness data derived from a meta-analysis on PST and/or PSM. Sensitivity and scenario analyses were performed to assess uncertainty on budget-impact analysis results.

RESULTS

Increasing PST and/or PSM usage in the national cohort from the current 15.4% to 50% resulted in savings ranging from €8 million after the first year to €184 million after 5 years. Further increases in the use of PST and/or PSM produced greater savings. Sensitivity analyses revealed budget-impact model sensitivity to the baseline and relative risks of thromboembolic complications. Unfavorable budget impact was found in scenarios exploring an increase in the use of PST alone as well as an increase in the market share of PST and PSM in patients with atrial fibrillation.

CONCLUSIONS

Overall study findings indicated that PST and PSM are more favorable alternatives to monitoring at specialized centers in patients without atrial fibrillation.

Real-world characteristics of hospitalized frail elderly patients with atrial fibrillation: can we improve the current prescription of anticoagulants?

BACKGROUND

In elderly patients, especially those older than 80 years, atrial fibrillation (AF) is associated with an almost 25% increased risk of stroke. Stroke prophylaxis with anticoagulants is therefore highly recommended. The prevalence of factors that have been associated with a lower rate of prescription and adherence to anticoagulant therapy in these patients is little known. The objective of this study was to explore the clinical characteristics of elderly subjects, with and without AF, consecutively admitted to an acute geriatric unit, discussing factors that may decrease the persistence on stroke prophylaxis therapy. We also highlight possible strategies to overcome the barriers conditioning the current underuse of oral anticoagulants in this segment of the population.

METHODS

A retrospective observational study was performed on a cohort of elderly patients with and without AF admitted to the Acute Geriatric Unit of San Gerardo Hospital (Monza, Italy).

RESULTS

Compared to patients without AF (n = 1216), those with AF (n = 403) had a higher Charlson Comorbidity Index (3 vs. 2, P < 0.001), number of administered drugs (4 vs. 3, P < 0.001), rate of heart failure (36.5% vs. 12%, P < 0.001) and chronic kidney disease (20.6 vs. 13.2, P < 0.001). Many patients with AF were frail (54%) or pre-frail (29%).

CONCLUSIONS

Elderly patients with AF have higher rates of conditions that affect adherence to traditional anticoagulant therapy (vitamin K antagonists, VKA). New direct oral anticoagulants (DOAs) can help overcome this problem. In order to prescribe the most appropriate VKA or DOAs, with the best efficacy/safety profile and the highest compliance, a comprehensive geriatric assessment should always accompany the scores for thrombotic and hemorrhagic risk stratification.

Rivaroxaban for thromboprophylaxis after total hip or knee arthroplasty: a meta-analysis with trial sequential analysis of randomized controlled trials

Venous thromboembolism (VTE) is the most widespread severe complication after total hip arthroplasty (THA) and total knee arthroplasty (TKA). We conducted this meta-analysis to further validate the benefits and harms of rivaroxaban use for thromboprophylaxis after THA or TKA. We thoroughly searched PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials. Trial sequential analysis (TSA) was applied to test the robustness of our findings and to obtain a more conservative estimation. Of 316 articles screened, nine studies were included. Compared with enoxaparin, rivaroxaban significantly reduced symptomatic VTE (P = 0.0001) and symptomatic deep vein thrombosis (DVT; P = 0.0001) but not symptomatic pulmonary embolism (P = 0.57). Furthermore, rivaroxaban was not associated with an increase in all-cause mortality, clinically relevant non-major bleeding and postoperative wound infection. However, the findings were accompanied by an increase in major bleeding (P = 0.02). The TSA demonstrated that the cumulative z-curve crossed the traditional boundary but not the trial sequential monitoring boundary and did not reach the required information size for major bleeding. Rivaroxaban was more beneficial than enoxaparin for preventing symptomatic DVT but increased the risk of major bleeding. According to the TSA results, more evidence is needed to verify the risk of major bleeding with rivaroxaban.

Assessment of Drug-Drug Interaction between Warfarin and Aprepitant and Its Effects on PT-INR of Patients Receiving Anticancer Chemotherapy

Aprepitant is a known inducer of CYP2C9, the main warfarin-metabolizing enzyme. Consequently, co-administration of these two drugs may result in reduction of the anticoagulation activity of warfarin. However, the nature and degree of time-dependent changes in prothrombin time international normalized ratio (PT-INR) after aprepitant and warfarin co-treatment in patients receiving anticancer chemotherapy has not been elucidated. We retrospectively examined the changes in warfarin dose, PT-INR, and warfarin sensitivity index (WSI; average of PT-INR value/average of daily warfarin dose) during four weeks, i.e., one week before and three weeks after aprepitant administration. The mean and standard deviation values of WSI for one week before and one, two, and three weeks after the beginning of aprepitant administration were 0.51±0.22 (1.00, n=34), 0.74±0.30 (1.53±0.59, n=30), 0.38±0.15 (0.82±0.22, n=28), and 0.46±0.29 (0.87±0.23, n=24), respectively. Values in parentheses represent relative changes versus WSI of one week before and number of subjects. Although the mean value of WSI significantly increased one week after aprepitant administration compared to that at one week before the administration, it in turn significantly decreased two weeks after compared to one week before (paired t-test, p<0.05 after Bonferoni correction). In patients taking warfarin, PT-INR should be carefully monitored for at least two weeks after the beginning of aprepitant administration because it may fluctuate with both aprepitant and chemotherapy during this period.

Discrepancies between Patients' Preferences and Educational Programs on Oral Anticoagulant Therapy: A Survey in Community Pharmacies and Hospital Consultations

Background

Oral anticoagulation therapy is increasingly used for the prevention and treatment of thromboembolic complications in various clinical situations. Nowadays, education programs for patients treated with anticoagulants constitute an integrated component of their management. However, such programs are usually based on the healthcare providers’ perceptions of what patients should know, rather than on patients’ preferences.

Objective

To investigate patients’ viewpoints on educational needs and preferred modalities of information delivery.

Methods

We conducted an observational study based on a self-administered questionnaire. To explore several profiles of patients, the study was designed for enrolling patients in two settings: during outpatient consultations in a cardiology department (Saint Antoine Hospital, Paris, France) and in community pharmacies throughout France.

Results

Of the 371 patients who completed the questionnaire, 187 (50.4%) were recruited during an outpatient consultation and 184 (49.6%) were recruited in community pharmacies. 84.1% of patients were receiving a vitamin K antagonist and 15.6% a direct oral anticoagulant. Patients ranked 16 of 21 (76.2%) questionnaire items on information about their treatment as important or essential; information on adverse effects of treatment was the highest ranked domain (mean score 2.38, 95% CI 2.30–2.46). Pharmacists (1.69, 1.58–1.80), nurses (1.05, 0.95–1.16), and patient associations (0.36, 0.29–0.44), along with group sessions (0.85, 0.75–0.95), the internet (0.77, 0.67–0.88), and delivery of material at the patient’s home (1.26, 1.14–1.38), were ranked poorly in terms of delivering educational material.

Conclusion

This study revealed substantial discrepancies between patient preferences and current educational programs. These findings should be useful for tailoring future educational programs that are better adapted to patients, with a potential associated enhancement of their effectiveness.

Recent advances in anticoagulant drug delivery

INTRODUCTION

Anticoagulants have been prescribed to patients to prevent deep vein thrombosis or pulmonary embolism. However, because of several problems in anticoagulant therapy, much attention has been directed at developing an ideal anticoagulant, and numerous attempts have been made to develop new anticoagulant delivery systems in recent years.

AREAS COVERED

This review discusses the challenges associated with the recent development of anticoagulants and their delivery systems. Various delivery methods have been developed to improve the use of anticoagulants. Recent advances in anticoagulant delivery and antidote development are also discussed in the context of their current progression states.

EXPERT OPINION

There have been many different approaches to developing the delivery system of anticoagulants. One approach has been to expand the use of new oral agents and develop their antidotes. Reducing the size of heparins to use smaller heparins for delivery, and developing oral or topical heparins are also some of the approaches used. Various physical formulations or chemical modifications are other ways that have enhanced the therapeutic potential of anticoagulant agents. On the whole, recent advances have contributed to increasing the efficacy and safety of anticoagulant clinically and have benefited the field of anticoagulant delivery.

The evolution of anticoagulant therapy

Arterial and venous thromboembolism are leading causes of morbidity and mortality around the world. For almost 70 years, heparins (unfractionated heparin and low molecular weight heparins) and vitamin K antagonists have been the leading therapeutic medical options for the treatment and prevention of thromboembolic disorders. Nevertheless, the many limitations of these traditional anticoagulants have fuelled the search for novel agents over the past 15 years, and a new class of oral anticoagulants that specifically target activated factor X and thrombin has been developed and is now commercially available. In this narrative review, the evolution of anticoagulant therapy is summarised, with a focus on newer oral anticoagulants.

Oral direct factor Xa inhibitor versus enoxaparin for thromboprophylaxis after hip or knee arthroplasty: Systemic review, traditional meta-analysis, dose-response meta-analysis and network meta-analysis

OBJECTIVES

To analyze the efficacy and safety of direct factor Xa inhibitors for thromboprophylaxis after total hip or knee replacement. To delineate the dose response effect of direct factor Xa inhibitors. To compare the efficacy between any two direct factor Xa inhibitors.

DESIGN

Systemic review, traditional meta-analysis, dose-response meta-analysis and network meta-analysis.

DATA SOURCE

PubMed, EMBASE and Cochrane Library.

STUDY SELECTION

Randomized controlled trials of rivaroxaban, apixaban, betrixaban, darexaban and edoxaban were compared with enoxaparin for thromboprophylaxis after total hip or knee replacement. Two reviewers independently checked the quality of RCTs. Another two investigators independently extracted data. The primary efficacy outcomes (composite of deep venous thrombosis, non-fatal pulmonary embolism and death of all causes) and the primary bleeding outcomes (major bleeding and non-major but clinically relevant bleeding) were summarized for meta-analysis. Stata software was used for traditional meta-analysis and dose-response meta-analysis, and Winbugs software was used for network meta-analysis.

RESULTS

Twenty trials with 38,507 subjects in the intention-to-treat population were included. Compared with enoxaparin, the risk of total venous thromboembolism was lower with rivaroxaban (relative risk 0.70, 95% confidence interval 0.60 to 0.81), apixaban (0.62, 0.47 to 0.81), and edoxaban (0.62, 0.39 to 0.97) and similar to darexaban (0.96, 0.84 to 1.11) and betrixaban (1.28, 0.97 to 1.68). Compared with enoxaparin, the risk of major or clinically relevant non-major bleeding was higher with rivaroxaban (1.52, 1.14 to 2.02), lower with betrixaban (0.34, 0.14 to 0.84) and similar to apixaban (0.88, 0.73 to 1.05), darexaban (0.85, 0.66 to 1.09) or edoxaban (1.30, 0.72 to 2.33). The risk of major and clinically relevant non-major bleeding of rivaroxaban had a linear relationship with its treatment doses; the risk of total venous thromboembolism of betrixaban and darexaban had linear relationships with their respective treatment doses. There was no linear nor non-liner relationships between the effect of apixaban and its treatment dose. The ranking of total venous thromboembolism risk from low to high was: rivaroxaban, apixaban, edoxaban, enoxaparin, darexaban, and betrixaban. The ranking of major and clinically relevant non-major bleeding from low to high was: betrixaban, enoxaparin, darexaban, edoxaban, apixaban, and rivaroxaban.

CONCLUSIONS

Direct oral factor Xa inhibitors are more effective to prevent venous thromboembolism after total hip or knee replacement. Their anticoagulant effect was not necessarily compromised with a higher bleeding risk. Rivaroxaban, apixaban and edoxaban showed a better anticoagulant effect, as compared with enoxaparin. Rivaroxaban had a higher bleeding rate, while apixaban and edoxaban did not show significantly higher bleeding risks.

Macroscopic hematuria in patients on anticoagulation therapy

INTRODUCTION

Visible hematuria is not rare in patients on anticoagulant therapy. There is no consensus regarding the diagnostic approach for them; some authors suggest restricted volume of diagnostic procedures because of the low number of urological etiology found. Some antibiotics have been reported to potentiate the effect of oral anticoagulants.

MATERIAL AND METHODS

The study addresses the need for urological assessment of patients on anticoagulation therapy and the possible role of some drugs administrated simultaneously with an oral anticoagulant, for the onset of macroscopic hematuria. Patients hospitalized with hematuria, both with or without anticoagulation therapy, were investigated and followed up.

RESULTS

The onset of hematuria depends on the monitoring of oral anticoagulation. INR (International Normalized Ratio) value corresponds with the probability of non-urological etiology, where INR>4 carries relatively low risk for urological and malignant etiology. Some antibiotics may influence the anticoagulation effect, so INR value may be elevated and hematuria may occur.

CONCLUSIONS

Anticoagulation therapy should be administrated carefully and individually. The risk of urological etiology of hematuria is lower in patients on oral anticoagulants (especially when INR >4), however, it is not zero.

Horseshoe thrombus in a patient with mechanical prosthetic mitral valve: A case report and review of literature

Patients with prosthetic cardiac valves are at high risk for thromboembolic complications and need life long anticoagulation with warfarin, which can be associated with variable dose requirements and fluctuating level of systemic anticoagulation and may predispose to thromboembolic and or hemorrhagic complications. Prosthetic cardiac valve thrombosis is associated with high morbidity and mortality. A high index of suspicion is essential for prompt diagnosis. Transthoracic echocardiography, and if required transesophageal echocardiography are the main diagnostic imaging modalities. Medically stable patients can be managed with thrombolytic therapy and anticoagulation, while some patients may require surgical thrombectomy or valve replacement. We present a case report of a patient with prosthetic mitral valve and an unusually large left atrial thrombus with both thromboembolic and hemorrhagic complications.

Dabigatran is Less Effective Than Warfarin at Attenuating Mechanical Heart Valve-Induced Thrombin Generation

Background

Patients with mechanical heart valves (MHV) require warfarin to prevent thromboembolism. Although dabigatran was as effective as warfarin for stroke prevention in atrial fibrillation when compared with warfarin in patients with MHV, the study was stopped early because of more strokes and bleeding with dabigatran. To determine why dabigatran was less effective than warfarin, we compared their effects on thrombin generation induced by MHV.

Methods and Results

Thrombin generation in the absence or presence of valve leaflets or sewing ring segments (SRS) was quantified. Studies were done in control plasma, plasma depleted of factors (F) XII, XI, or VII, plasma containing varying concentrations of dabigatran, or plasma from patients on dabigatran or warfarin with varying dabigatran concentrations or international normalized ratio (INR) values. Mean endogenous thrombin potential (ETP) increased 1.2-, 1.5-, and 1.8-fold in the presence of leaflets, Teflon SRS, and Dacron SRS, respectively. Whereas ETP in FVII-depleted and control plasma was similar, ETP was reduced to background levels in FXII-depleted plasma and abrogated in FXI-depleted plasma. Dabigatran had little effect on ETP at concentrations below 400 ng/mL, whereas in plasma from warfarin-treated patients, ETP was suppressed with INR values over 1.5.

Conclusions

MHV induce thrombin generation via the intrinsic pathway and generate sufficient thrombin to overwhelm clinically relevant dabigatran concentrations. In contrast, warfarin is more effective than dabigatran at suppressing MHV-induced thrombin generation. These data explain why dabigatran failed in MHV patients and suggest that strategies targeting FXII or FXI may suppress the root cause of thrombosis in such patients.

Pharmacogenetics in Jewish populations

Spanning over 2000 years, the Jewish population has a long history of migration, population bottlenecks, expansions, and geographical isolation, which has resulted in a unique genetic architecture among the Jewish people. As such, many Mendelian disease genes and founder mutations for autosomal recessive diseases have been discovered in several Jewish groups, which have prompted recent genomic studies in the Jewish population on common disease susceptibility and other complex traits. Although few studies on the genetic determinants of drug response variability have been reported in the Jewish population, a number of unique pharmacogenetic variants have been discovered that are more common in Jewish populations than in other major racial groups. Notable examples identified in the Ashkenazi Jewish (AJ) population include the vitamin K epoxide reductase complex subunit 1 (VKORC1) c.106G>T (p.D36Y) variant associated with high warfarin dosing requirements and the recently reported cytochrome P450 2C19 (CYP2C19) allele, CYP2C19*4B, that harbors both loss-of-function [*4 (c.1A>G)] and increased-function [*17 (c.-806C>T)] variants on the same haplotype. These data are encouraging in that like other ethnicities and subpopulations, the Jewish population likely harbors numerous pharmacogenetic variants that are uncommon or absent in other larger racial groups and ethnicities. In addition to unique variants, common multi-ethnic variants in key drug metabolism genes (e.g., ABCB1, CYP2C8, CYP2C9, CYP2C19, CYP2D6, NAT2) have also been detected in the AJ and other Jewish groups. This review aims to summarize the currently available pharmacogenetics literature and discuss future directions for related research with this unique population.

New oral anticoagulants: their role in stroke prevention in high-risk patients with atrial fibrillation

Based on efficacy, safety, and ease of use, novel oral anticoagulants will likely replace VKAs for many if not most patients with atrial fibrillation. Novel anticoagulants have a lower rate of intracranial hemorrhage compared with vitamin K antagonists. The incidence of other life-threatening bleeds is similar if not lower. Dose adjustments need to be made based on renal function and advanced age. There is at present a need for an antidote for these new drugs.

New anticoagulants in the management of venous thromboembolism in women

Objective diagnosis and treatment are important in optimizing clinical outcomes in patients with venous thromboembolism (VTE), and anticoagulants are the mainstay of treatment. Traditionally, anticoagulant therapy involves parenteral anticoagulants, overlapping with and followed by oral vitamin K antagonists. Recently, direct oral anticoagulants (DOACs), including the Factor Xa inhibitors rivaroxaban, apixaban and edoxaban, and the direct thrombin inhibitor dabigatran etexilate, have been developed to address limitations associated with traditional anticoagulant therapy. DOACs have recently been approved for the treatment of acute deep vein thrombosis (DVT) and pulmonary embolism (PE). Successful phase III trials have demonstrated their efficacy for the treatment of DVT and PE, with a potentially improved safety profile. Recent evidence suggests that women bleed more compared to men when treated with DOACs for VTE without differences in treatment efficacy. Future clinical trials should include outcomes stratified by sex, and should investigate the clinical impact of this sex-related safety difference.

The management of dental patients taking new generation oral anticoagulants

Recently, new oral anticoagulants have been introduced as alternatives to warfarin. While national guidelines for treatment of dental patients taking warfarin as an anticoagulant are well-established, no such information is available for these novel therapeutic agents. At present, the local guidance available is contradictory between different health boards/health planning units, and liaison with the medical practitioner managing the individual patient's anticoagulation is imperative if any invasive procedure is proposed. This paper examines the available evidence regarding these drugs and sets out proposals for clinical guidance of dental practitioners treating these patients in primary dental care.

Total burden of intraplaque hemorrhage in coronary arteries relates to the use of coumarin-type anticoagulants but not platelet aggregation inhibitors

Intraplaque hemorrhage (IPH) is a crucial factor in progression and destabilization of an atherosclerotic plaque. Anti-thromboembolic drugs are widely used as prophylactic treatment against arterial and venous thrombotic diseases, but a major complication is bleeding. We investigated the association between exposure to anti-thromboembolic therapy and IPH in postmortem coronary arteries. Coronary arteries with postmortem angiographically confirmed extensive atherosclerosis were obtained at autopsy from patients who had received oral anticoagulants (n = 10), platelet aggregation inhibitors (n = 10), or no anti-thrombotic drugs (n = 10) before death. Coronary arteries were cut at 3-mm interval, and all plaque-containing segments were immunohistochemically screened for IPH and microvessels. These data were related to overall plaque composition and the use of anti-thromboembolic therapies. IPH was found in 483 out of 904 (53 %) coronary segments with advanced atherosclerotic plaques and more frequently in patients on oral anticoagulants (174/284, 61 %) than in patients on anti-platelets (198/376, 53 %) or without therapy (111/244, 46 %) (P = 0.02 and P = 0.001, respectively). Also, intraplaque microvascular leakage was more frequently observed in patients on anticoagulants than in non-treated patients (P = 0.03). Finally, the IPH appeared to be larger in plaques of patients on anticoagulant treatment (P < 0.001). Density of intraplaque microvessels was highest in plaques of patients on platelet inhibitors (P < 0.05), but this was not associated with increased hemorrhagic burden. Prophylactic therapy with oral coumarin-type anticoagulants appears to be associated with a higher hemorrhagic burden in atherosclerotic coronary arteries, which may lead to increase in plaque volume over time, in this selected subgroup of patients.

The role of the novel oral anticoagulants in the secondary prevention of acute coronary syndromes

Acute coronary syndromes continue to be a dominant cause of death worldwide. Acute therapies with potent antithrombotic agents have improved in-hospital outcomes; however, despite the use of these therapies, recurrent events continue to occur long term. Statins, renin-angiotensin inhibitors, beta-blockers, and dual antiplatelet therapy all have roles in mitigating long-term risk, but given recurrent thrombotic events on contemporary pharmacologic agents, novel therapies inhibiting thrombin formation have been explored. The intent of the current article is to review recent phase II/III clinical trials of oral anticoagulants used for the prevention of acute coronary syndromes.