New oral anticoagulants for stroke prevention in atrial fibrillation: impact of study design, double counting and unexpected findings on interpretation of study results and conclusions

Nanobodies against factor XI apple 3 domain inhibit binding of factor IX and reveal a novel binding site for high molecular weight kininogen

BACKGROUND

Factor XI (FXI) is a promising target for novel anticoagulants because it shows a strong relation to thromboembolic diseases, while fulfilling a mostly supportive role in hemostasis. Anticoagulants targeting FXI could therefore reduce the risk for thrombosis, without increasing the chance of bleeding side effects.

OBJECTIVES

To generate nanobodies that can interfere with FXIa mediated activation of factor IX (FIX).

METHODS

Nanobodies were selected for binding to the apple 3 domain of FXI and their effects on FXI and coagulation were measured in purified protein systems as well as in plasma-based coagulation assays. Additionally, the binding epitope of selected nanobodies was assessed by hydrogen-deuterium exchange mass spectrometry.

RESULTS

We have identified five nanobodies that inhibit FIX activation by FXI by competing with the FIX binding site on FXI. Interestingly, a sixth nanobody was found to target a different binding epitope in the apple 3 domain, resulting in competition with the FXI-high molecular weight kininogen (HK) interaction.

CONCLUSIONS

We have characterized a nanobody targeting the FXI apple 3 domain that elucidates the binding orientation of HK on FXI. Moreover, we have produced five nanobodies that can inhibit the FXI-FIX interaction.

Bleeding Risk Following Stereotactic Body Radiation Therapy for Localized Prostate Cancer in Men on Baseline Anticoagulant or Antiplatelet Therapy

Purpose

Patients on anticoagulant/antiplatelet medications are at a high risk of bleeding following external beam radiation therapy for localized prostate cancer. SBRT may reduce the bleeding risk by decreasing the volume of bladder/rectum receiving high doses. This retrospective study sought to evaluate the rates of hematuria and hematochezia following SBRT in these patients.

Methods

Localized prostate cancer patients treated with SBRT from 2007 to 2017 on at least one anticoagulant/antiplatelet at baseline were included. The minimum follow-up was 3 years with a median follow-up of 72 months. Patients who had a rectal spacer placed prior to SBRT were excluded. Radiotherapy was delivered in 5 fractions to a dose of 35 Gy or 36.25 Gy utilizing the CyberKnife system. Hematuria and hematochezia were prospectively assessed before and after treatment using the Expanded Prostate Cancer Index Composite (EPIC-26). Toxicities were scored using the CTCAE v4. Cystoscopy and colonoscopy findings were retrospectively reviewed.

Results

Forty-four men with a median age of 72 years with a history of taking at least one anticoagulant and/or antiplatelet medication received SBRT. Warfarin (46%), clopidogrel (34%) and rivaroxaban (9%) were the most common medications. Overall, 18.2% experienced hematuria with a median time of 10.5 months post-SBRT. Altogether, 38.6% experienced hematochezia with a median time of 6 months post-SBRT. ≥ Grade 2 hematuria and hematochezia occurred in 4.6% and 2.5%, respectively. One patient required bladder neck fulguration and one patient underwent rectal cauterization for multiple non-confluent telangiectasia. There were no grade 4 or 5 toxicities. Cystoscopy revealed bladder cancer (40%) and benign prostatic bleeding (40%) as the most common hematuria etiology. Colonoscopy demonstrated hemorrhoids (54.5%) and radiation proctitis (9.1%) as the main causes of hematochezia. There was no significant change from the mean baseline EPIC-26 hematuria and hematochezia scores at any point during follow up.

Conclusion

In patients with baseline anticoagulant usage, moderate dose prostate SBRT was well tolerated without rectal spacing. High grade bleeding toxicities were uncommon and resolved with time. Baseline anticoagulation usage should not be considered a contraindication to prostate SBRT.

Updates in Anticoagulation Therapy Monitoring

In the past six decades, heparin and warfarin were the primary anticoagulants prescribed for treatment and prophylaxis of venous thromboembolism worldwide. This has been accompanied by extensive clinical knowledge regarding dosing, monitoring, and reversal of these anticoagulants, and the resources required to do so have largely been readily available at small and large centers alike. However, with the advent of newer oral and parenteral anticoagulants such as low molecular weight heparins, factor Xa inhibitors, and direct thrombin inhibitors in recent years, new corresponding practice guidelines have also emerged. A notable shift in the need for monitoring and reversal agents has evolved as well. While this has perhaps streamlined the process for physicians and is often desirable for patients, it has also left a knowledge and resource gap in clinical scenarios for which urgent reversal and monitoring is necessary. An overview of the currently available anticoagulants with a focus on the guidelines and available tests for anticoagulant monitoring will be discussed in this article.

Direct oral anticoagulants: evidence and unresolved issues

Currently licenced direct oral anticoagulants selectively target thrombin (eg, dabigatran) or coagulation factor Xa (eg, apixaban, betrixaban, edoxaban, and rivaroxaban). Designed to be given in fixed doses without routine monitoring, direct oral anticoagulants have a lower propensity for food and drug interactions than do vitamin K antagonists, and in randomised controlled trials involving around 250 000 patients, they were at least as effective for prevention and treatment of thrombosis and were associated with a lower risk of life-threatening bleeding. The absolute benefits of direct oral anticoagulants over vitamin K antagonists are modest; however, guidelines recommend them in preference to vitamin K antagonists for most indications because of their ease of use and superior safety. The greatest benefits of direct oral anticoagulants are likely to be in patients who were previously deemed unsuitable for vitamin K antagonist therapy. The emergence of generic preparations is expected to further increase the uptake of direct oral anticoagulants, particularly in countries where they are currently not widely used because of cost. Direct oral anticoagulants are contraindicated in patients with mechanical heart valves and should be used with caution or avoided in patients with advanced kidney or liver disease. In this Therapeutics paper, we review the pharmacology of direct oral anticoagulants, summarise the evidence that led to their approval and incorporation into treatment guidelines, and explore key unresolved issues. We also briefly discuss future perspectives for the development of oral anticoagulants.

Clinically relevant drug interactions between newer antidepressants and oral anticoagulants

Introduction: This is a review of the drug interactions (DIs) between newer antidepressants and oral anticoagulants (OACs): vitamin K antagonists (VKAs) and direct-acting OACs (DOACs).Areas covered: Articles were obtained from PubMed searches performed for each of the newer antidepressants and oral anticoagulants. The basic pharmacokinetic and pharmacodynamic mechanisms for DIs with these drugs were summarized. Some newer antidepressants are inhibitors of a number of cytochrome P450 (CYP) isoforms and many antidepressants appear to have potential to impair serotonin platelet function and increase bleeding risk.Expert opinion: Clinicians should not forget that the DIs between newer antidepressants and VKAs can be potentially lethal. Among SSRIs, fluoxetine and fluvoxamine appear to be associated with the highest DI risk with warfarin, the most commonly prescribed VKA worldwide. Case reports featuring duloxetine, mirtazapine and trazadone suggested potential for interaction with warfarin. As CYP3A4 is an important metabolic pathway for all DOACs except dabigatran, it appears reasonable to recommend avoiding the co-prescription of fluoxetine and fluvoxamine (weak to moderate CYP3A4 inhibitors) and St John's wort (CYP3A4 inducer). Many package inserts for the newer antidepressants include a warning regarding an increased risk of bleeding events with concomitant use of these agents with OACs.

Rivaroxaban versus Low-Molecular-Weight Heparin for Venous Thromboembolism in Gastrointestinal and Pancreatobiliary Cancer

BACKGROUND

Low-molecular-weight heparin (LMWH) is the standard treatment for venous thromboembolism (VTE) in patients with active cancer. However, use of factor Xa inhibitors, such as rivaroxaban, is increasing on the basis of limited clinical evidence. The present single-center study compared the incidence of bleeding and other treatment outcomes in gastrointestinal and pancreatobiliary cancer (GI tract cancer) patients administered rivaroxaban or LMWH for the treatment of VTE.

METHODS

Retrospective data from 281 GI tract cancer patients who were treated for VTE with rivaroxaban (n = 78) or LMWH (n = 203) between 1 January 2012 and 31 December 2016, were analyzed. Primary end-point was the incidence of major and clinically relevant bleeding. Secondary outcomes included the incidence of recurrent VTE and mortality.

RESULTS

Clinically relevant bleeding occurred in 19 patients (24.4%) in the rivaroxaban group and 31 (15.3%) in the LMWH group (P = 0.074). No inter-group difference was observed for rate of VTE recurrence (3.8% with rivaroxaban vs. 3.9% with LMWH; P > 0.999) or incidence of major bleeding (5.1% with rivaroxaban vs. 8.9% with LMWH; P = 0.296). Multivariate Cox proportional hazards analysis for age, cancer type, metastasis, history of chemotherapy or recent surgery, and Eastern Cooperative Oncology Group performance status revealed a 1.904-fold higher risk of bleeding with rivaroxaban than LMWH (1.031-3.516; P = 0.040). No significant inter-group difference was found in terms of hazard ratio for all-cause mortality.

CONCLUSION

Compared to LMWH, rivaroxaban was associated with a higher incidence of clinically relevant bleeding in GI tract cancer patients presenting with VTE.

A Retrospective Study on Efficacy and Safety of Rivaroxaban and Dalteparin for Long-Term Treatment of Venous Thromboembolism in Patients with Lung Cancer

BACKGROUND

Standard therapy for cancer-associated venous thromboembolism (VTE) is low-molecular-weight heparin. The use of direct oral anticoagulants for cancer-associated VTE has increased; however, their efficacy and safety in lung cancer patients remain unclear.

OBJECTIVES

We examined the efficacy and safety of rivaroxaban compared with dalteparin for cancer-associated VTE in patients with primary lung cancer.

METHODS

A single-center retrospective study of 204 patients with primary lung cancer who were prescribed rivaroxaban (n = 131) or dalteparin (n = 73) for VTE was performed. The primary endpoint was a composite event including recurrence and major or clinically relevant nonmajor bleeding. Secondary endpoints included the incidence of recurrence, major and clinically relevant nonmajor bleeding, all-cause mortality, and bleeding or pulmonary embolism-related mortality.

RESULTS

The composite event occurred in 38 (29.0) and 12 (16.4%) patients in the rivaroxaban and dalteparin (p = 0.045) groups, respectively. The multivariate Cox proportional hazards model for age, Eastern Cooperative Oncology Group performance score, and bleeding risk factors revealed the rivaroxaban group showed a 1.176-fold composite event risk without statistical significance (0.595-2.324, p = 0.641). There was no statistically significant intergroup difference for the incidence of VTE recurrence (5.3% in the rivaroxaban group versus 2.7% in the dalteparin group, p = 0.495) and major or clinically relevant nonmajor bleeding (23.7% in the rivaroxaban group versus 13.7% in the dalteparin group, p = 0.089). There was no significant difference in the all-cause mortality rate (hazard ratio 0.864, 95% CI 0.624-1.196, p = 0.337).

CONCLUSIONS

There was no difference in the safety and efficacy profile of rivaroxaban compared with dalteparin. Therefore, rivaroxaban may be a valuable treatment option for lung cancer-associated VTE.

A direct oral factor Xa inhibitor edoxaban ameliorates neointimal hyperplasia following vascular injury and thrombosis in apolipoprotein E-deficient mice

Vascular injury activates the coagulation cascade. Some studies report that coagulation factor Xa and thrombin are implicated in proliferation of vascular smooth muscle cells and neointimal hyperplasia after vascular injury. The aim of this study was to determine the effect of an oral direct factor Xa inhibitor, edoxaban, on neointimal hyperplasia following the carotid artery injury in apolipoprotein E (ApoE)-deficient mice. Vascular injury was induced by the application of 10% ferric chloride to the carotid artery for 3 min in ApoE-deficient mice. After vascular injury, all animals were fed with high-cholesterol chow for 6 weeks. Edoxaban at 15 mg/kg was orally administered to the mice 1 h before (n = 10) or 1 h after (n = 9) ferric chloride injury, and thereafter 10 mg/kg edoxaban was orally administered b.i.d. for 6 weeks. Thrombus formation and neointimal hyperplasia were evaluated. Treatment with 15 mg/kg edoxaban before vascular injury almost completely inhibited thrombus formation, and following chronic administration of edoxaban significantly suppressed neointimal hyperplasia. In the mice treated with edoxaban after vascular injury, there was wide interindividual variability. In some mice (four out of nine) the neointimal hyperplasia was inhibited like in edoxaban-pretreated mice, but there was no statistical difference compared with control. This study demonstrated that inhibition of the coagulation and thrombosis by edoxaban ameliorated neointimal hyperplasia caused by vascular injury and high-cholesterol diets in ApoE-deficient mice. This suggests that factor Xa has a crucial role in the formation of neointima following vascular injury.The abstract should be followed by 3-4 bullet points that highlight major findings. The final bullet point should emphasize future directions for research.

Comparing intracerebral hemorrhages associated with direct oral anticoagulants or warfarin

OBJECTIVES

This cross-sectional survey explored the characteristics and outcomes of direct oral anticoagulant (DOAC)-associated nontraumatic intracerebral hemorrhages (ICHs) by analyzing a large nationwide Japanese discharge database.

METHODS

We analyzed data from 2,245 patients who experienced ICHs while taking anticoagulants (DOAC: 227; warfarin: 2,018) and were urgently hospitalized at 621 institutions in Japan between April 2010 and March 2015. We compared the DOAC- and warfarin-treated patients based on their backgrounds, ICH severities, antiplatelet therapies at admission, hematoma removal surgeries, reversal agents, mortality rates, and modified Rankin Scale scores at discharge.

RESULTS

DOAC-associated ICHs were less likely to cause moderately or severely impaired consciousness (DOAC-associated ICHs: 31.3%; warfarin-associated ICHs: 39.4%; p = 0.002) or require surgical removal (DOAC-associated ICHs: 5.3%; warfarin-associated ICHs: 9.9%; p = 0.024) in the univariate analysis. Propensity score analysis revealed that patients with DOAC-associated ICHs also exhibited lower mortality rates within 1 day (odds ratio [OR] 4.96, p = 0.005), within 7 days (OR 2.29, p = 0.037), and during hospitalization (OR 1.96, p = 0.039).

CONCLUSIONS

This nationwide study revealed that DOAC-treated patients had less severe ICHs and lower mortality rates than did warfarin-treated patients, probably due to milder hemorrhages at admission and lower hematoma expansion frequencies.

Use of Guidelines for Reducing Stroke Risk in Patients With Nonvalvular Atrial Fibrillation: A Review From a Latin American Perspective

Atrial fibrillation (AF) is a prominent risk factor for stroke and a leading cause of death and disability throughout Latin America. Contemporary evidence-based guidelines for the management of AF and stroke incorporate the use of practical and relatively simple scoring methods to estimate both stroke and bleeding risk, in order to assist in matching patients with appropriate interventions. This review examines consistencies and differences among guidelines for reducing stroke risk in patients with AF, assessing the role of user-friendly scoring methods to determine appropriate patients for anticoagulation and other treatment options. Current options include warfarin and direct oral anticoagulants such as dabigatran, rivaroxaban, apixaban, and edoxaban. These agents have been found to be superior or noninferior to standard vitamin K antagonist anticoagulation in large randomized trials. Potential benefits of these agents mainly include lower ischemic stroke rates, reduced intracranial bleeding, no need for regular monitoring, and fewer drug-drug and drug-food interactions. Expert opinions regarding clinical situations for which data are presently lacking, such as emergency bleeding and stroke in anticoagulated patients, are also provided. Enhanced attention and adherence to evidence-based guidelines are essential components for a strategy to reduce stroke morbidity and mortality across Latin America.

Evolving Treatments for Arterial and Venous Thrombosis: Role of the Direct Oral Anticoagulants

The direct oral anticoagulants (DOACs) represent a major advance in oral anticoagulant therapy and have replaced the vitamin K antagonists as the preferred treatment for many indications. By simplifying long-term anticoagulant therapy and improving its safety, the DOACs have the potential to reduce the global burden of thrombosis. Postmarketing studies suggest that the favorable results achieved with DOACs in the randomized controlled trials can be readily translated into practice, but highlight the need for appropriate patient, drug and dose selection, and careful follow-up. Leveraging on their success to date, ongoing studies are assessing the utility of DOACs for the prevention of thrombosis in patients with embolic stroke of unknown source, heart failure, coronary artery disease, peripheral artery disease, antiphospholipid syndrome, and cancer. The purpose of this article is to (1) review the pharmacology of the DOACs, (2) describe the advantages of the DOACs over vitamin K antagonists, (3) summarize the experience with the DOACs in established indications, (4) highlight current challenges and limitations, (5) highlight potential new indications; and (6) identify future directions for anticoagulant therapy.

New anticoagulants for the treatment of venous thromboembolism

Worldwide, venous thromboembolism (VTE) is among the leading causes of death from cardiovascular disease, surpassed only by acute myocardial infarction and stroke. The spectrum of VTE presentations ranges, by degree of severity, from deep vein thrombosis to acute pulmonary thromboembolism. Treatment is based on full anticoagulation of the patients. For many decades, it has been known that anticoagulation directly affects the mortality associated with VTE. Until the beginning of this century, anticoagulant therapy was based on the use of unfractionated or low-molecular-weight heparin and vitamin K antagonists, warfarin in particular. Over the past decades, new classes of anticoagulants have been developed, such as factor Xa inhibitors and direct thrombin inhibitors, which significantly changed the therapeutic arsenal against VTE, due to their efficacy and safety when compared with the conventional treatment. The focus of this review was on evaluating the role of these new anticoagulants in this clinical context.

Old and new oral anticoagulants: Food, herbal medicines and drug interactions

The most commonly prescribed oral anticoagulants worldwide are the vitamin K antagonists (VKAs) such as warfarin. Factors affecting the pharmacokinetics of VKAs are important because deviations from their narrow therapeutic window can result in bleedings due to over-anticoagulation or thrombosis because of under-anticoagulation. In addition to pharmacodynamic interactions (e.g., augmented bleeding risk for concomitant use of NSAIDs), interactions with drugs, foods, herbs, and over-the-counter medications may affect the risk/benefit ratio of VKAs. Direct oral anticoagulants (DOACs) including Factor Xa inhibitors (rivaroxaban, apixaban and edoxaban) and thrombin inhibitor (dabigatran) are poised to replace warfarin. Phase-3 studies and real-world evaluations have established that the safety profile of DOACs is superior to those of VKAs. However, some pharmacokinetic and pharmacodynamic interactions are expected. Herein we present a critical review of VKAs and DOACs with focus on their potential for interactions with drugs, foods, herbs and over-the-counter medications.

The Sex, Age, Medical History, Treatment, Tobacco Use, Race Risk (SAMe TT2R2) Score Predicts Warfarin Control in a Singaporean Population

BACKGROUND

Warfarin reduces stroke risk in atrial fibrillation (AF) patients but requires ongoing monitoring. Time in therapeutic range (TTR) is used as a measure of warfarin control, with a TTR less than 60% associated with adverse patient outcomes. The Sex, Age, Medical history, Treatment, Tobacco use, Race (SAMe-TT₂R₂) score has been identified as a model able to predict warfarin control, but this has been tested in mainly Caucasian populations. Therefore, the aim of this study was to determine the ability of the SAMe-TT₂R₂ score to predict warfarin control in a Singaporean population consisting of Chinese, Malay, and Indian race.

METHODS

Retrospective data were collected from the National Heart Centre Singapore for AF patients receiving warfarin between January and June 2014. The TTR and the SAMe-TT₂R₂ score were calculated for each patient.

RESULTS

The 1137 non-valvular AF patients had a mean TTR of 58.0 ± 34.3% and a median SAMe-TT₂R₂ score of 3. The categorized SAMe-TT₂R₂ scores (2 versus >2) showed a significant reduction in mean TTR for the entire population (63.2% versus 55.8%, P = .0004) and also when categorized according to race for Chinese (62.7% versus 56.9%, P = .0075) and Malay (68.4% versus 50.6%, P = .0131) populations.

CONCLUSION

The SAMe-TT₂R₂ tool is effective in predicting warfarin control in a Singaporean population as patients with a score greater than 2 had poor control. The minimum score for non-Caucasian patients is 2; thus, in these patients, the presence of any additional risk factors identified in the SAMe-TT₂R₂ tool categorizes them as unlikely to achieve adequate warfarin control and possible candidates for alternative anticoagulants.

Reducing The Risk Of Stroke In Patients With Nonvalvular Atrial Fibrillation With Direct Oral Anticoagulants. Is One Of These Not Like The Others?

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and increases risk of stroke by nearly 5-fold. While warfarin has been employed successfully to reduce the risk of stroke in these patients, there are a number of challenges with therapy. These include the need for therapeutic monitoring due to variability in patient response, frequent dose adjustments, numerous drug-drug, drug-food, and drug-disease interactions, and a heightened risk of thrombosis and bleeding due to these issues. Current guidelines recommend that the vitamin K antagonists (VKA) or direct oral anticoagulants (DOACs) should be used for thromboprophylaxis in patients with nonvalvular AF at risk for stroke or systemic embolic events. The DOACs include the direct thrombin inhibitor dabigatran and the direct factor Xa inhibitors rivaroxaban, apixaban, and edoxaban. In clinical trials these agents consistently demonstrated a reduction in the risks of hemorrhagic stroke and intracranial hemorrhage compared to VKA. Clinicians now must decide if there are meaningful differences between these agents in order to prescribe the best agent for an individual patient. Therefore, it is critical for clinicians to go beyond information provided in manuscript abstracts, and gain an understanding of the similarities and differences in clinical trial design, patient enrollment, and statistical analysis.

Prevention of arterial thrombosis by edoxaban, an oral factor Xa inhibitor in rats: monotherapy and in combination with antiplatelet agents

In addition to platelet aggregation, coagulation activation is considered to be involved in arterial thrombosis. In this study, we determined antithrombotic effects of edoxaban, an oral factor Xa (FXa) inhibitor, as both a monotherapy and in combination with antiplatelet agents in a rat model of arterial thrombosis. We further examined its effects on a procoagulant biomarker and bleeding. Arterial thrombosis was induced by topical application of 15% ferric chloride to rat abdominal aortas. Bleeding time was measured by a tail incision method. Edoxaban, clopidogrel, and aspirin were orally administered 30min, 4h, and 2h before thrombus or bleeding induction. As a biomarker of coagulation activation, plasma thrombin-antithrombin complex (TAT) was measured. Edoxaban dose-dependently prevented arterial thrombosis in a manner comparable to clopidogrel and aspirin. The combination of edoxaban plus clopidogrel or edoxaban plus aspirin significantly potentiated the antithrombotic effects compared with these drugs alone. The combination of edoxaban and clopidogrel was more potent than clopidogrel and aspirin. Plasma TAT concentration was elevated after thrombus induction and suppressed by edoxaban and clopidogrel, but not by aspirin, suggesting P2Y12 receptor-mediated platelet procoagulant activity. Bleeding time was prolonged by the coadministration of edoxaban and clopidogrel, but not by edoxaban and aspirin. In conclusion, the present study demonstrates that the monotherapy with edoxaban and combination therapy with edoxaban plus clopidogrel or edoxaban plus aspirin are promising options for the prevention of arterial thrombosis as effective as the standard antiplatelet agents; however, a combination of edoxaban and clopidogrel increased the risk of bleeding.

Edoxaban in venous thromboembolism and stroke prevention: an appraisal

Oral anticoagulation is the therapeutic cornerstone in preventing thromboembolic risk in both atrial fibrillation (AF) and venous thromboembolism (VTE). After decades of the sole therapeutic oral anticoagulation option being warfarin, the introduction of non-vitamin K antagonist oral anticoagulants has heralded a new era. Edoxaban is the latest addition to these available for clinical use. Edoxaban was as effective and safer than warfarin in preventing thromboembolic risk in AF patients. Similarly, edoxaban effectiveness and safety was evident when treating VTE patients to prevent recurrent VTE or VTE-related death. Therefore, edoxaban represents a valuable alternative in treating thromboembolic risk for AF and VTE patients.

How to choose appropriate direct oral anticoagulant for patient with nonvalvular atrial fibrillation

The novel oral anticoagulants or direct oral anticoagulants (DOAC) are becoming more common in clinical practice for the prevention of stroke in non-valvular atrial fibrillation (NVAF). The availability of several agents with similar efficacy and safety for stroke prevention in NVAF patients offers more selection, but at the same time requires certain knowledge to make a good choice. This comparative analysis provides an appraisal of the respective clinical trials and highlights much of what remains unknown about four FDA-approved agents: dabigatran, apixaban, rivaroxaban, and edoxaban. It details how the DOACs compare to warfarin and to one another summarizes pharmacologic and pharmacodynamic properties, and drug interactions from the stand point of practical consequences of these findings. Common misconceptions and reservations are addressed. The practical application of this data is intended to help choosing the most appropriate agent for individual NVAF patient.

Assessment of the Quality of Chronic Anticoagulation Control With Time in Therapeutic Range in Atrial Fibrillation Patients Treated With Vitamin K Antagonists by Hemostasis Specialists: The TERRA Registry: Tiempo en rango en la República Argentina

BACKGROUND

Oral anticoagulation therapy with vitamin K antagonists (VKA) such as warfarin and acenocoumarol is recommended in patients with atrial fibrillation (AF) and risk factors for embolism. The quality of anticoagulation control with VKA may be assessed by the time in therapeutic range (TTR). In our country, there are no data available about the quality of anticoagulation in patients with AF. The primary goal of our study was to assess the level of effective anticoagulation in a multicenter network of anticoagulation clinics in Argentina, which included patients with nonvalvular AF (NVAF) treated with VKA oral anticoagulants.

METHODS

The TERRA trial is a multicenter, cross-sectional study involving 14 anticoagulation clinics that were invited to participate and recruit 100 consecutive patients with NVAF treated with VKA for more than 1 year. The international normalized ratio (INR) values were retrospectively obtained from patient charts, and TTR was calculated using the Rosendaal method.

RESULTS

A total of 1190 patients were included in the analysis. Mean age was 74.9 ± 9.9 years, and 52.5% of the patients were male. Median TTR was 67.5% (interquartile interval 54-80). During 55% of the TTR, INR was >3. Interinstitution variability was substantial, with a range of 57.7% ± 17% to 87.7% ± 17%, P < .001. The 10th percentile of TTR was 41%, the 20th percentile was 50%, the 30th was 58%, and the 35th percentile was 60%. In 40% of patients, TTR was <70%.

CONCLUSION

In this multicenter study, mean TTR values in patients with AF under VKA were similar to those in international therapeutic clinical trials (55%-65%). Marked variations among institutions were observed and, although average results obtained were high, one third of the patients exhibited a TTR below 60%. This cutoff value is conservative according to current recommendations, and guidelines suggest that when management with VKA cannot be improved, patients should be switched to direct oral anticoagulants. The addition of TTR calculation to clinical practice may help improve the quality of oral anticoagulation in patients with AF, thus improving anticoagulation outcomes.

How to choose appropriate direct oral anticoagulant for patient with nonvalvular atrial fibrillation

The novel oral anticoagulants or direct oral anticoagulants (DOAC) are becoming more common in clinical practice for the prevention of stroke in non-valvular atrial fibrillation (NVAF). The availability of several agents with similar efficacy and safety for stroke prevention in NVAF patients offers more selection, but at the same time requires certain knowledge to make a good choice. This comparative analysis provides an appraisal of the respective clinical trials and highlights much of what remains unknown about four FDA-approved agents: dabigatran, apixaban, rivaroxaban, and edoxaban. It details how the DOACs compare to warfarin and to one another summarizes pharmacologic and pharmacodynamic properties, and drug interactions from the stand point of practical consequences of these findings. Common misconceptions and reservations are addressed. The practical application of this data is intended to help choosing the most appropriate agent for individual NVAF patient.

Edoxaban for reducing the risk of stroke and systemic embolism in patients with non-valvular atrial fibrillation

INTRODUCTION

Oral anticoagulation is central to the management of patients with atrial fibrillation (AF) and at least one additional stroke risk factor. For decades, the vitamin K antagonists (e.g. warfarin) remained the only oral anticoagulant available for stroke prevention in AF. The non-vitamin K oral anticoagulants (NOACs) are now available, and these drugs include the direct thrombin inhibitors and factor Xa inhibitors. The latter class includes edoxaban, which has recently been approved for stroke prevention in AF by the United States Food and Drug Administration and the European Medicine Agency. In line with other NOACs, edoxaban avoids the many limitations of warfarin associated with variability of anticoagulation effect and multiple food and drug interactions.

AREAS COVERED

In this review, the currently available evidence on edoxaban in patients with non-valvular AF is discussed. The pharmacology, efficacy and safety, and current aspects of use of edoxaban in patients with non-valvular AF for stroke and thromboembolism prevention are reviewed.

EXPERT OPINION

Phase III trials on edoxaban for stroke prevention in non-valvular AF confirms non-inferiority of edoxaban compared to well-managed warfarin both in terms of efficacy and safety. Currently ongoing and future trials as well as real-world data are warranted to confirm its effectiveness and safety for chronic anticoagulation and improve evidence in other areas which are lacking evidence where NOAC use remains controversial.

Gastrointestinal bleeding in patients receiving oral anticoagulation: Current treatment and pharmacological perspectives

Gastrointestinal bleeding (GIB) is a potentially fatal and avoidable medical condition that poses a burden on global health care costs. The rate of major GIB related to the use of some direct acting oral anticoagulant drugs (DOACs), is higher than that detected in warfarin users. Current strategies in the treatment of GIBs in patients receiving warfarin or DOACs (vitamin K, activated charcoal; hemodialysis; recombinant factor VIIa; [activated] prothrombin complex concentrates) including indications for the treatment of bleeding based on different degrees of severity of the episodes, is reported in this article. Potential preventive strategies to mitigate the risk of GIBs (e.g. upper endoscopy/biopsy, colon cancer screening; eradication of Helicobacter pylori prior to starting anticoagulation; use of proton-pump inhibitors, identification of risk factors for bleeding) are also reported as well as the fact that some of them have not been tested so far in patients receiving DOACs. Antidotes that experimentally reverse the anti-coagulant effect of dabigatran (Idarucizumab; BI 655075; Boehringer Ingelheim); of rivaroxaban, apixaban, or edoxaban (Andexanet alfa, r-Antidote, PRT064445; Portola Pharmaceuticals) or of all DOACs (Aripazine, PER-977, ciraparantag; Perosphere Inc.) are discussed. Likewise, population pharmacokinetics modeling related to the rate of major DOACs-related GIBs is presented. It is also emphasized that the occurrence of GIB reflects the presence of patients at the highest risk for adverse outcomes. Finally, the implications of the concept that patient characteristics and the severity of illness (i.e. comorbidities) exert a greater impact on the risk of GIB than the type of antithrombotic agent employed, are analyzed.

Composite end point analyses of non-vitamin K antagonist oral anticoagulants compared with warfarin in patients with atrial fibrillation

OBJECTIVE

Non-vitamin K antagonist oral anticoagulants (NOACs) have been proposed as alternatives to vitamin K antagonists (VKAs). The aim of this study is to examine the efficacy and safety of NOACs compared with warfarin with composite end points in patients with atrial fibrillation.

METHODS

This semi-systematic review performed a study of Phase III randomized controlled trials comparing NOACs with vitamin K antagonists (VKAs) in patient with atrial fibrillation using composite end points (combination of various clinical events). The use of composite end points allowed for combining efficacy and safety outcomes, thereby comparing the differences between NOAC and warfarin therapy from a clinical perspective.

RESULTS

Treatment with NOAC compared with warfarin was associated with a significant reduction in the sum of stroke or non-CNS, systemic embolism and major bleeding (odds ratio 0.87; 95% CI: 0.82-0.91).

CONCLUSION

Generally, NOACs were associated with a more favorable efficacy and safety profile compared with warfarin with regard to composite end points.

Preventing Thrombosis to Improve Outcomes in Heart Failure Patients

Heart failure (HF) is associated with an increased risk of thrombotic events, particularly if this condition is accompanied by atrial fibrillation (AF). Many HF patients have background coronary artery disease (CAD) making them prone to coronary thrombosis resulting in myocardial infarction or sudden death. Oral anticoagulation is essential in the vast majority of HF patients with AF with non-vitamin K based anticoagulants being a suitable alternative to warfarin. In contrast, aspirin alone does not provide adequate stroke prevention in such patients. In HF without AF, oral anticoagulation should not be routinely used, and antiplatelet agents should be prescribed in patients with background CAD. This review provides an overview of prothrombotic factors and antithrombotic management of patients with HF.

Direct Oral Anticoagulants for the Prevention of Stroke in Patients with Nonvalvular Atrial Fibrillation: Understanding Differences and Similarities

The presence of atrial fibrillation (AF), the most common sustained cardiac arrhythmia, significantly increases the risk for stroke. Current guidelines recommend that the vitamin K antagonist warfarin or direct oral anticoagulants (DOACs), such as the approved direct thrombin inhibitor dabigatran and the approved direct factor Xa inhibitors apixaban, rivaroxaban, and edoxaban, should be used for thromboprophylaxis in patients with nonvalvular AF at risk for stroke or systemic embolic events (SEE). Warfarin, the mainstay of stroke prevention in AF, increases the risk of major bleeding. Furthermore, warfarin therapy comes with several limitations including frequent monitoring and the need for dose adjustments, unpredictable pharmacokinetics and pharmacodynamics, and the potential for significant drug-drug and food-drug interactions. The DOACs were developed to overcome these limitations while maintaining or surpassing warfarin's efficacy and safety profiles. All four DOACs have similar or better efficacy and safety compared with warfarin and are therefore valuable alternatives for the prevention of stroke and SEE in patients with nonvalvular AF. Understanding the subtle differences in the DOACs' pharmacology, phase 3 study designs, and trial outcomes will allow for a more tailored approach in selecting the right oral anticoagulant for each patient.

Restarting Anticoagulant Treatment After Intracranial Hemorrhage in Patients With Atrial Fibrillation and the Impact on Recurrent Stroke, Mortality, and Bleeding

Background—

Intracranial hemorrhage is the most feared complication of oral anticoagulant treatment. The optimal treatment option for patients with atrial fibrillation who survive an intracranial hemorrhage remains unknown. We hypothesized that restarting oral anticoagulant treatment was associated with a lower risk of stroke and mortality in comparison with not restarting.

Methods and Results—

Linkage of 3 Danish nationwide registries in the period between 1997 and 2013 identified patients with atrial fibrillation on oral anticoagulant treatment with incident intracranial hemorrhage. Patients were stratified by treatment regimens (no treatment, oral anticoagulant treatment, or antiplatelet therapy) after the intracranial hemorrhage. Event rates were assessed 6 weeks after hospital discharge and compared with Cox proportional hazard models. In 1752 patients (1 year of follow-up), the rate of ischemic stroke/systemic embolism and all-cause mortality (per 100 person-years) for patients treated with oral anticoagulants was 13.6, in comparison with 27.3 for nontreated patients and 25.7 for patients receiving antiplatelet therapy. The rate of ischemic stroke/systemic embolism and all-cause mortality (per 100 person-years) for recurrent intracranial hemorrhage, the rate of ischemic stroke/systemic embolism, and all-cause mortality (per 100 person-years) patients treated with oral anticoagulants was 8.0, in comparison with 8.6 for nontreated patients and 5.3 for patients receiving antiplatelet therapy. The adjusted hazard ratio of ischemic stroke/systemic embolism and all-cause mortality was 0.55 (95% confidence interval, 0.39–0.78) in patients on oral anticoagulant treatment in comparison with no treatment. For ischemic stroke/systemic embolism and for all-cause mortality, hazard ratios were 0.59 (95% confidence interval, 0.33–1.03) and 0.55 (95% confidence interval, 0.37–0.82), respectively.

Conclusions—

Oral anticoagulant treatment was associated with a significant reduction in ischemic stroke/all-cause mortality rates, supporting oral anticoagulant treatment reintroduction after intracranial hemorrhage as feasible. Future trials are encouraged to guide clinical practice in these patients.

New-onset atrial fibrillation after recent coronary stenting: Warfarin or non-vitamin K-antagonist oral anticoagulants to be added to aspirin and clopidogrel? A viewpoint

The antithrombotic management of patients on oral anticoagulation (OAC), with either warfarin or non-vitamin K-antagonist oral anticoagulants (NOACs), undergoing percutaneous coronary intervention with stent (PCI-S) has been recently addressed in a joint European consensus document. In accordance, triple therapy (TT) of OAC, aspirin and clopidogrel should generally be given as the initial therapy. More uncertainty exists over whether warfarin or a NOAC should be added in patients already on dual antiplatelet therapy of aspirin and clopidogrel (DAPT) after recent PCI-S. Upon review of available data, it appears that the risk of major bleeding of TT as compared to DAPT is similar with either warfarin or a NOAC. In particular, TT consistently appears associated to an approximately 2.5 fold increase in the risk of major bleeding. Because of the higher convenience, NOACs might be considered the preferred OAC to be added to DAPT. Given the reported different safety profiles of the various NOACs on the incidence of major, and gastrointestinal, bleeding, the NOACs, and the dose, showing the greatest safety in this regard should be selected. In accordance, dabigatran 110 mg and apixaban 2.5mg twice daily appear as the most valuable options in patients who are not and who are respectively, at increased risk of bleeding. As an alternative, apixaban 5mg twice daily might be considered in patients at risk of bleeding not increased, whereas rivaroxaban 15 mg once daily may be considered in the presence of increased risk of bleeding (essentially when related to moderate renal impairment).

Antithrombotic drugs, patient characteristics, and gastrointestinal bleeding: Clinical translation and areas of research

Gastrointestinal bleeding (GIB) is a potentially fatal and avoidable medical condition that poses a burden on global health care costs. Current understanding of the roles of platelet activation and thrombin generation/activity in vascular medicine has led to the development of effective antithrombotic treatments. However, in parallel with a sustained coronary and cerebral flow patency, the increasingly intensive treatment with warfarin; direct oral anticoagulant drugs [DOACs], and/or with aspirin ± clopidogrel (or ± prasugrel or ± ticagrelor), has increased the burden of GIBs related to the use of antithrombotic agents. Compelling evidence concerning this issue is accumulating to indicate that: 1) the risk of GIB related to the use of antithrombotic drugs dramatically differs in different clinical settings; and 2) the characteristics of patients (e.g., severity of illness, comorbidities) in whom it is used exert a greater impact on the risk of GIB than the type of antithrombotic agent employed. The latter concept argues for the occurrence of GIB as reflecting the presence of patients at the highest risk for adverse outcomes. The HAS-BLED score identifies subjects at risk of bleeding among those untreated and those treated with warfarin, DOACs and/or low-dose aspirin. Its use within the frame of a severity score (e.g., the CHA2DS2-VASc score in patients with atrial fibrillation) helps balance the benefits and the risks of an antithrombotic treatment and identify those patients in whom the absolute gain (vascular events prevented) outweighs the risk of GIB. Potential implications of the latter information in settings other than atrial fibrillation is thoroughly discussed.

Selection of Warfarin or One of the New Oral Antithrombotic Agents for Long-Term Prevention of Stroke among Persons with Atrial Fibrillation

OPINION STATEMENT

Atrial fibrillation (AF) is the most common sustained cardiac rhythm disorder, which can potentially increases the risk of stroke by five-fold, thus, resulting in high public healthcare burden. Stroke prevention is vital in the management of AF patients. Vitamin K antagonists (VKA, eg, warfarin) have been the mainstay treatment to prevent ischemic stroke and systemic thromboembolism in AF patients for several decades. Despite the efficacy of warfarin, its limitations have recently driven the advent of some new antithrombotic agents, the non-VKA oral anticoagulant (NOACs, including dabigatran, rivaroxaban, apixaban, and edoxaban). The NOACs have changed the landscape for thromboembolic prophylaxis among patients with nonvalvular AF. Although three NOACs thus far (dabigatran, rivaroxaban, and apixaban) have been approved in Europe and the United States, for stroke prevention in patients with nonvalvular AF on the basis of several Phase III clinical trials, warfarin still remain important in preventing stroke for patients. This is especially true for those with optimal control of international normalized ratio with high (>70 %) time in therapeutic range, valvular AF or associated prosthetic valve. These NOACs are attractive alternatives for stroke prevention in patients with nonvalvular AF who are unable or unwilling to receive warfarin. However, several issues should be taken into consideration on safe and effective use of these NOACs in day-to-day clinical practice, for example, pharmacological properties, drug interactions, monitoring and compliance, and treatment of frail elderly patients or patients with renal impairment, etc. The decision about whether to initiate oral anticoagulation either with warfarin or NOACs should be patient-centered and after consideration of both stroke and bleeding risks. It is important for clinical practitioner to offer patients with AF an individualized decision about drug choice, making decision after adequate patient education plus discussion about the risks and benefits of these agents, thus fitting the drug to the patient profile.