Evaluation of Prescribing Practices and Outcomes Using Direct-acting Oral Anticoagulants After Cardiac Surgery

PurposeCardiac surgery patients frequently require anticoagulation. Warfarin remains the preferred agent, and a few trials have reported negative outcomes with the use of direct-acting oral anticoagulants (DOACs) in these patients. Therefore, limited literature exists that supports the dosing, safety, and efficacy of DOACs within the cardiac surgery population.MethodsThis single-center, retrospective analysis was conducted at a tertiary academic medical center. All data were extrapolated from electronic medical records of qualifying patients from August 2017 to August 2019. Adult patients were included if they received at least 1 of 4 DOACs (apixaban, rivaroxaban, edoxaban, or dabigatran) after undergoing one of the following cardiac surgeries: coronary artery bypass graft, bioprosthetic valve replacement, aortic surgery, or valve repair. The composite safety end point included major bleeding and clinically relevant nonmajor bleeding, as defined by the International Society on Thrombosis and Hemostasis. The composite efficacy outcome of thromboembolic events included deep vein thrombosis, pulmonary embolism, ischemic stroke, and intracardiac thrombus.FindingsA total of 305 patient charts were identified for analysis; 229 patients met the inclusion criteria. The composite safety outcome occurred in 12 patients (5.2%) within 90 days after cardiac surgery. One patient (0.4%) experienced a thromboembolic event within 90 days after cardiac surgery. The most commonly prescribed DOAC was apixaban (79.0%). US Food and Drug Administration–approved dosing was used in 91.3% of patients, and DOACs were primarily used for the indication of stroke prevention in atrial fibrillation or atrial flutter (88.2%).ImplicationsThese data provide insight into the prescribing practices, efficacy, and safety of DOACs in cardiac surgery patients.     

Clinical review: Clinical management of new oral anticoagulants: a structured review with emphasis on the reversal of bleeding complications

New oral anticoagulants, including dabigatran, rivaroxaban, and apixaban, have been recently approved for primary and secondary prophylaxis of thromboembolic conditions. However, there is no clear strategy for managing and reversing their anticoagulant effects. We aimed to summarize the available evidence for clinical management and reversal of bleeding associated with new oral anticoagulants. Using a systematic review approach, we aimed to identify studies describing reversal strategies for dabigatran, rivaroxaban, and apixaban. The search was conducted using Medline, EMBASE, HealthSTAR, and grey literature. We included laboratory and human studies. We included 23 studies reported in 37 out of 106 potentially relevant references. Four studies were conducted in humans and the rest were in vitro and in vivo studies. The majority of the studies evaluated the use of prothrombinase complex concentrate (PCC), either activated or inactivated, and recombinant activated factor VII (rFVIIa). Other interventions were also identified. Laboratory studies suggest that hemostatic parameters and bleeding might be partially or completely corrected by PCC for rivaroxaban better than dabigatran. Studies in humans suggest that PCC might reverse the effects of rivaroxaban better than dabigatran assessed by hemostatic tests. We were not able to locate studies evaluating the clinical efficacy of these agents. The best available evidence suggests that PCC (activated or inactivated) might be the best option for reversing new anticoagulants. Evidence for rFVIIa is less compelling. There might be differences in the efficacy of reversing agents for different anticoagulants. Studies assessing the clinical efficacy of these reversal agents are urgently needed.     

Hemorrhagic risk and intracranial complications in patients with minor head injury (MHI) taking different oral anticoagulants

The correlation between direct oral anticoagulants (DOACs) or Vitamin K Antagonist (VKAs) intake and the incidence of intracranial complications after minor head injury (MHI) is still object of debate: preliminary observation seems to demonstrate lower incidence in intracranial bleeding complications (ICH) in patients taking DOACs than VKA. METHODS. This prospective and observational study was performed to clarify the incidence of ICH in patients in DOACs compared to VKAs. Between January 2016 and April 2018 we have recorded in our ED patients with MHI taking oral anticoagulants. Their hemorragic risk score was calculated and recorded for each patient (Has Bled, Atria and Orbit). RESULTS A total of 402 patients with MHI taking anticoagulant were collected: 226 were receiving one of the four DOACs (dabigatran, rivaroxaban, apixaban or edoxaban) while 176 patients were in therapy with VKA. The rate of intracranial complications was significantly lower in patients receiving DOACs than in patients treated with VKA (p < 0.01). In the VKA group two patients died because of intracranial bleeding. No deaths were recorded in the DOACs group. DISCUSSION patients with MHI who take DOACs have a significant lower incidence of intracranial bleeding complications than those treated with vitamin k antagonists. This statement is supported by the observation that the hemorrhagic risk, measured according to the chosen scores, was similar between the two groups.     

Direct Oral Anticoagulants Compared With Dalteparin for Treatment of Cancer-Associated Thrombosis: A Living,Interactive Systematic Review and Network Meta-analysis

ObjectiveTo maintain living, interactive evidence (LIvE) on the benefits and harms of different treatment options in adults with cancer-associated thrombosis (CAT).MethodsWe have used a novel LIvE synthesis framework to maintain this living, interactive systematic review since September 19, 2018. Randomized controlled trials evaluating the efficacy and safety of direct oral anticoagulants (DOACs) compared with low-molecular-weight heparin for CAT are included in this analysis. Details of LIvE synthesis framework are available at the website https://cat.network-meta-analysis.com.ResultsThe results are constantly updated as new information becomes available (https://cat.network-meta-analysis.com/CAT.html). The living, interactive systematic review currently includes 4 randomized controlled trials (N=2894). Direct comparisons show that DOACs significantly decrease recurrent venous thromboembolism (VTE) events compared with dalteparin (odds ratio [OR], 0.59; 95% CI, 0.41 to 0.86; I², 25%) without significantly increasing major bleeding (OR, 1.34; 95% CI, 0.83 to 2.18; I², 28%). Mixed treatment comparisons show that apixaban (OR, 0.41; 95% credible interval [CrI], 0.16 to 0.95) and rivaroxaban (OR, 0.58; 95% CrI, 0.37 to 0.90) significantly decrease VTE recurrent events compared with dalteparin. Edoxaban significantly increases major bleeding compared with dalteparin (OR, 1.73; 95% CrI, 1.04 to 3.16), and rivaroxaban significantly increases clinically relevant nonmajor bleeding compared with dalteparin and other DOACs. There are no significant differences between DOACs in terms of VTE recurrences and major bleeding.ConclusionDOACs should be considered a standard of care for the treatment of CAT except in patients with a high risk of bleeding. Current evidence favors the use of apixaban for the treatment of CAT among other DOACs.RegistrationOpen Science Framework (https://osf.io/dth86).     

A review of guidelines on anticoagulation reversal across different clinical scenarios – Is there a general consensus?

Anticoagulation is key to the treatment/prevention of thromboembolic events. The primary complication of anticoagulation is serious or life-threatening hemorrhage, which may necessitate prompt anticoagulation reversal; this could also be required for nonbleeding patients requiring urgent/emergent invasive procedures. The decision to reverse anticoagulation should weigh the benefit–risk ratio of supporting hemostasis versus post-reversal thrombosis. We appraise the available guidelines/recommendations for vitamin K antagonist (VKA) and direct oral anticoagulant (DOAC) reversal in the management of major bleeding, and also assess recent clinical data that may not yet be reflected in official guidance. In general, available guidelines are consistent in their recommendations, advocating administration of vitamin K and 4-factor prothrombin complex concentrates (4F-PCCs) rather than fresh frozen plasma to patients with VKA-associated intracranial hemorrhage and life-threatening bleeding, and specific reversal agents as essential therapy for DOAC reversal in those same severe conditions. However, guidelines also recommend off-label use of PCCs for DOAC reversal when specific reversal agents are unavailable. Limited recent evidence generally support the latter recommendation, but guidelines are likely to evolve as more data become available.     

Direct Oral Factor Xa Inhibitors for the Treatment of Acute Cancer-Associated Venous Thromboembolism: A Systematic Review and Network Meta-analysis

ObjectiveTo explore the efficacy and safety of direct oral factor Xa inhibitors in the treatment of cancer-associated acute venous thromboembolism (VTE).Patients and MethodsMEDLINE, CENTRAL (Cochrane Central Register of Controlled Trials), and Embase databases were searched for trials comparing direct oral anticoagulants (DOACs) to dalteparin for the management of cancer-associated acute VTE. Databases were searched from inception to September 19, 2018. A network meta-analysis using both frequentist and Bayesian methods was performed to analyze VTE recurrence and major and clinically relevant nonmajor bleeding.ResultsWe identified 3 randomized controlled trials, at low risk of bias, that enrolled 1739 patients with cancer-associated VTE. Direct comparison revealed a lower rate of VTE recurrence in DOAC compared with dalteparin groups (odds ratio [OR], 0.48; 95% CI, 0.24-0.96; I²=46%). Indirect comparison suggested that apixaban had greater reduction in VTE recurrence compared with dalteparin (OR, 0.10; 95% CI, 0.01-0.82) but not rivaroxaban or edoxaban. Apixaban also had the highest probability of being ranked most effective. By direct comparisons, there was an increased likelihood of major bleeding in the DOAC group compared with dalteparin (OR, 1.70; 95% CI, 1.04-2.78). Clinically relevant nonmajor bleeding did not differ. Indirect estimates were imprecise. Subgroup analyses in gastrointestinal cancers suggested that dalteparin may have the lowest risk of bleeding, whereas estimates in urothelial cancer were imprecise.ConclusionDirect oral anticoagulants appear to lower the risk of VTE recurrence compared with dalteparin while increasing major bleeding. Apixaban may be associated with the lowest risk of VTE recurrence compared with the other DOACs.     

Anticoagulation in atrial fibrillation: a new era has begun

Atrial fibrillation is one of the most frequent reasons for therapeutic anticoagulation in everyday practice. Oral vitamin K antagonists such as Marcumar have been state of the art anticoagulants to prevent thrombembolic events in patients with atrial fibrillation and additional risk factors. But these drugs are accompanied by disadvantages such as increased bleeding risk and impaired quality of life caused by interactions with food or other medications as well as frequent controls of INRs. The new anticoagulants apixaban, rivaroxaban and dabigatran are direct antagonists of coagulation factors (FXa or FIIa) and demonstrate a promising risk/benefit profile in large clinical trials compared with vitamin K antagonists. Their approval for clinical use will open up new therapeutic perspectives for patients with atrial fibrillation and indication for anticoagulation.     

Recommendations for the emergency management of complications associated with the new direct oral anticoagulants (DOACs), apixaban, dabigatran and rivaroxaban

Dabigatran, apixaban, and rivaroxaban have been approved for primary and secondary stroke prevention in patients with atrial fibrillation. However, questions have arisen about how to manage emergency situations, such as when thrombolysis would be required for acute ischemic stroke or for the managing intracranial or gastrointestinal bleedings. We summarize the current literature and provide recommendations for the management of these situations. Peak plasma levels of the direct oral anticoagulants (DOACs) apixaban, dabigatran, or rivaroxaban are observed about 2–4 h after intake. Elimination of dabigatran is mainly dependent on renal function. Consequently, if renal function is impaired, there is a risk of drug accumulation that is highest for dabigatran followed by rivaroxaban and then apixaban and thus dosing recommendations are different. To date, no bedside tests are available that reliably assess the anticoagulatory effect of DOACs, nor are specific antidotes available. We recommend performing the following tests if DOAC intake is unknown: dabigatran-associated bleeding risk is minimized or can be neglected if thrombin time, Hemoclot test, or Ecarin clotting time is normal. Apixaban and rivaroxaban effects can be ruled out if findings from the anti-factor Xa activity test are normal. High plasma levels of DOAC are also mostly excluded if PTT and PTZ are normal four or more hours after DOAC intake. However, normal values of global coagulation tests are not sufficient if thrombolysis is indicated for treating acute stroke. The decision for or against thrombolysis is an individual decision; in these cases, thrombolysis use is off-label. In case of bleeding, prothrombin complex concentrates seems to be the most plausible treatment. For severe gastrointestinal bleeding with life-threatening blood loss, the bleeding source needs to be identified and treated by invasive measures. Use of procoagulant drugs (antifibrinolytics) might also be considered. However, there is very limited clinical experience with these products in conjunction with DOAC.     

Bench-to-bedside review: Optimising emergency reversal of vitamin K antagonists in severe haemorrhage – from theory to practice

Critical care physicians are increasingly facing patients receiving oral anticoagulation for either cessation of major haemorrhage or to reverse the effects of vitamin K antagonists ahead of emergency surgery. Rapid reversal of anticoagulation is particularly essential in cases of life-threatening bleeding. In these situations, guidelines recommend the concomitant administration of prothrombin complex concentrates (PCCs) and oral or intravenous vitamin K for the fastest normalisation of the international normalised ratio (INR). Despite their universal recommendation, PCCs remain underused by many physicians who prefer to opt for fresh frozen plasma despite its limitations in anticoagulant reversal, including time to reverse INR and high risk of transfusion-related acute lung injury. In contrast, the lower volume required to normalise INR with PCCs and the room temperature storage facilitate faster preparation and administration time, thus increasing the speed at which haemorrhages can be treated. PCCs therefore allow faster, more reliable and complete reversal of vitamin K anticoagulation, especially when administered immediately following confirmation of haemorrhage. In the emergency setting, probabilistic dosing may be considered.     

Bench-to-bedside review: Optimising emergency reversal of vitamin K antagonists in severe haemorrhage – from theory to practice

Critical care physicians are increasingly facing patients receiving oral anticoagulation for either cessation of major haemorrhage or to reverse the effects of vitamin K antagonists ahead of emergency surgery. Rapid reversal of anticoagulation is particularly essential in cases of life-threatening bleeding. In these situations, guidelines recommend the concomitant administration of prothrombin complex concentrates (PCCs) and oral or intravenous vitamin K for the fastest normalisation of the international normalised ratio (INR). Despite their universal recommendation, PCCs remain underused by many physicians who prefer to opt for fresh frozen plasma despite its limitations in anticoagulant reversal, including time to reverse INR and high risk of transfusion-related acute lung injury. In contrast, the lower volume required to normalise INR with PCCs and the room temperature storage facilitate faster preparation and administration time, thus increasing the speed at which haemorrhages can be treated. PCCs therefore allow faster, more reliable and complete reversal of vitamin K anticoagulation, especially when administered immediately following confirmation of haemorrhage. In the emergency setting, probabilistic dosing may be considered.     

Real-world utilization of andexanet alfa

ObjectiveIn 2018, the FDA approved andexanet alfa for the reversal of life-threatening hemorrhages in patients anticoagulated with apixaban or rivaroxaban. Yet, cost-effective factor Xa inhibitor reversal remains controversial. The objective of this study was to describe real world utilization of andexanet alfa.MethodsThis was a retrospective case series of patients receiving andexanet alfa between July 28, 2018 and April 29, 2019 at a large academic health system. Baseline demographics, anticoagulant type and reversal, as well as brain imaging were collected. Primary endpoints were stability of hematoma for intracranial hemorrhage (ICH), and hemostatic effectiveness for patients undergoing surgical procedures. Secondary endpoints were thromboembolism and 30 day mortality.ResultsOf the 25 patients evaluated, 13 received andexanet alfa for ICH. Eleven of the 13 had follow-up imaging available and stability was observed in 90.9%. Three patients received andexanet alfa for reversal prior to surgical procedures, and 100% hemostatic effectiveness was achieved. Nine patients received andexanet alfa for reversal of extracranial bleeding, including gastrointestinal bleed (n=4). There were no thrombotic events in our cohort, and 30 day mortality was 24%. Sixty-four percent of patients would have met exclusion criteria for the ANNEXA-4 trial.ConclusionThis is the largest series to date describing real-world utilization of andexanet alfa. Our series showed hemostatic efficacy in 90.9% of patients with ICH, and 100% in patients undergoing surgical procedures. There were no thrombotic complications. Yet, larger and comparative studies are needed to clarify the optimal agent and patient selection for reversal of factor Xa inhibitors.     

The impact of prothrombin complex concentrates when treating DOAC-associated bleeding: a review

Background

Bleeding complications are a risk associated with all anticoagulants. Currently, the treatment options for the management of direct oral anticoagulant (DOAC)-associated bleeding are limited. Prothrombin complex concentrates (PCCs) have been proposed as a potential therapeutic option, and evidence regarding their use is increasing.

Review

Many studies supporting PCC have used preclinical models and healthy volunteers; however, more recently, observational studies have further improved insight into current DOAC reversal strategies. Multiple clinical practice guidelines now specifically suggest use of PCCs for this indication. Specific reversal agents for Factor Xa inhibitors may become available in the near future, but data on their efficacy are still emerging.

Conclusions

Ultimately, a multimodal approach may be the optimal strategy to restore haemostasis in patients presenting with DOAC-associated coagulopathy.

     

Novel Oral Anticoagulants for Stroke Prevention in Atrial Fibrillation: Focus on Apixaban

Stroke prevention in atrial fibrillation (AF) has been challenging over decades, mostly due to a number of difficulties associated with oral vitamin K antagonists (VKAs), which have been the most effective stroke prevention treatment for a long time. The oral direct thrombin inhibitors (e.g., dabigatran) and oral direct inhibitors of factor Xa (e.g., rivaroxaban, apixaban) have emerged recently as an alternative to VKAs for stroke prevention in AF. These drugs act rapidly, and have a predictable and stable dose-related anticoagulant effect with a few clinically relevant drug-drug interactions. The novel oral anticoagulants are used in fixed doses with no need for regular laboratory monitoring of anticoagulation intensity. However, each of these drugs has distinct pharmacological properties that could influence optimal use in clinical practice. The following phase 3 randomized trials with novel oral anticoagulants versus warfarin for stroke prevention in AF have been completed: the Randomized Evaluation of Long-term Anticoagulant therapy (RE-LY) trial with dabigatran, the Rivaroxaban Once daily oral direct Factor Xa inhibition Compared with vitamin K antagonism for prevention of stroke and Embolism Trial in Atrial Fibrillation (ROCKET-AF) trial with rivaroxaban, and the Apixaban for Reduction of Stroke and Other Thromboembolism Events in Atrial Fibrillation (ARISTOTLE) trial with apixaban. Moreover, the Apixaban Versus Acetylsalicylic Acid to prevent Strokes (AVERROES) trial included patients with AF who have failed or were unsuitable for warfarin, and compared apixaban versus aspirin for stroke prevention in AF. Overall, apixaban has two large trials for stroke prevention in AF showing benefits not only over warfarin, but also over aspirin among those patients who have failed or refused warfarin. In the ARISTOTLE trial, apixaban was superior to warfarin in the reduction of stroke or systemic embolism, major bleeding, intracranial hemorrhage, and all-cause mortality, with a similar reduction in the rate of ischemic stroke and better tolerability. When compared with aspirin in the AVERROES trial, apixaban was associated with more effective reduction of stroke, a similar risk of major bleeding, and better tolerability. In this review article, the authors summarize the current knowledge on novel oral anticoagulants and discuss the clinical aspects of their use for stroke prevention in AF, with particular emphasis on apixaban.     

Laboratory testing in patients treated with direct oral anticoagulants: a practical guide for clinicians

Click to hear Dr Baglin's perspective on the role of the laboratory in treatment with new oral anticoagulants

Summary

One of the key benefits of the direct oral anticoagulants (DOACs) is that they do not require routine laboratory monitoring. Nevertheless, assessment of DOAC exposure and anticoagulant effects may become useful in various clinical scenarios. The five approved DOACs (apixaban, betrixaban, dabigatran etexilate, edoxaban and rivaroxaban) have different characteristics impacting assay selection and the interpretation of results. This article provides an updated overview on (i) which test to use (and their advantages and limitations), (ii) when to assay DOAC levels, (iii) how to interpret the results relating to bleeding risk, emergency situations and perioperative management, and (iv) what is the impact of DOACs on routine and specialized coagulation assays. Assays for anti‐Xa or anti‐IIa activity are the preferred methods when quantitative information is useful, although the situations in which to test for DOAC levels are still debated. Different reagent sensitivities and variabilities in laboratory calibrations impact assay results. International calibration standards for all specific tests for each DOAC are needed to reduce the inter‐laboratory variability and allow inter‐study comparisons. The impact of the DOACs on hemostasis testing may cause false‐positive or false‐negative results; however, these can be minimized by using specific assays and collecting blood samples at trough concentrations. Finally, prospective clinical trials are needed to validate the safety and efficacy of proposed laboratory thresholds in relation to clinical decisions. We offer recommendations on the tests to use for measuring DOACs and practical guidance on laboratory testing to help patient management and avoid diagnostic errors.     

Different Coagulation Indicators in Predicting Clinical Outcomes for Patients With Direct Oral Anticoagulants: A Systematic Review and Meta-analysis

PurposeThere are many anticoagulant test indexes available for direct oral anticoagulants (DOACs), but how to select the appropriate index and the index cutoff values are still controversial. This is the first study, to our knowledge, to assess the association of different coagulation indicators with clinical outcomes among DOACs using a meta-analysis of observational studies.MethodsA medical literature search was conducted using PubMed, Web of Science, EMBASE, ClinicalTrials.gov, and the Cochrane Library from inception to February 2020. Studies that reported relationships between coagulation indexes and clinical outcomes or the diagnostic value of coagulation assays were included in the analysis.FindingsA total of 17 articles (7 meta-analyses and 10 systematic reviews) from 8904 citations were included in the analysis. In the analysis of bleeding events with coagulation indexes for DOACs, for peak prothrombin time level (cutoff value of 19–25 s), the pooled results found a sensitivity of 0.61 (95% CI, 0.44–0.75) and a specificity of 0.71 (95% CI, 0.49–0.86). For rivaroxaban, the trough anti–factor Xa concentration (AXA-C) (cutoff value of 400–500 ng/mL) had a sensitivity of 0.53 (95% CI, 0.16–0.87) and a specificity of 0.87 (95% CI, 0.71–0.94), with a diagnostic odds ratio of 7 (95% CI, 2–32). For apixaban, trough AXA-C had a sensitivity of 0.85 (95% CI, 0.60–0.96) and a specificity of 0.83 (95% CI, 0.52–0.95). The AUC of the AXA-C peak was higher than that of the trough AXA-C for apixaban, with a higher sensitivity and specificity. Compared with trough concentration of anti–factor IIa for dabigatran, the peak concentration had a higher specificity (98%) at the cutoff value of 484 ng/mL. In the analysis of thromboembolic events with coagulation indexes for DOACs, peak and trough prothrombin time values were not typically correlated with subsequent symptomatic venous thromboembolism, without a sensitivity or specificity higher than 90%. Trough AXA-C had a sensitivity of 100% and but a low specificity (<50%) for rivaroxaban-apixaban. Trough AXA-C had a sensitivity of 100% and a specificity of 32% with a cutoff value of 108 ng/mL for dabigatran.ImplicationPeak prothrombin time (19–25 s) and AXA-C had a better predictive value on bleeding outcomes for rivaroxaban and apixaban, whereas peak concentration of anti–factor IIa activity can be an indicator for dabigatran. Coagulation indexes might not be a good indicator of thromboembolic events of DOACs. Because the limited studies focused on association of coagulation indicators and clinical outcomes, more studies are needed to verify this in the future.     

Andexanet alfa for the reversal of factor Xa inhibitors

Introduction: Andexanet alfa is a recombinant modified factor Xa protein that has been developed to reverse factor Xa inhibitors. Since May 2018, the FDA has approved its utilization in patients treated with apixaban and rivaroxaban in case of life-threatening or uncontrolled bleeding. On 28 of February 2019, the Committee for Medicinal Products for Human Use adopted a positive opinion, recommending the granting of a conditional marketing authorization for andexanet alfa in Europe.

Area covered: The authors provide an overview of andexanet alfa development and its pharmacokinetic and pharmacodynamic properties. The results of the clinical phase III trial ANNEXA as well as current limitations related to andexanet alfa are also discussed.

Expert opinion: Although phase I and II studies have proven that andexanet alfa can be effective in reversing the effect of factor Xa inhibitors, its efficacy in major bleeding patients has only been shown for apixaban and rivaroxaban, without any comparator group. Well-designed studies comparing the efficacy and safety of andexanet alfa to other reversal strategies are required to confirm preliminary data. The benefit of andexanet alfa in specific settings needs to be investigated and its use in clinical practice needs to be facilitated by the implementation of international guidelines.     

Safety Signal Evaluation of a Risk of Syncope and Dizziness Not Related to Bleeding or Stroke in Direct Oral Anticoagulant–treated Patients

PurposeIn clinical studies, rivaroxaban treatment has been associated with increased incidence of syncope not related to bleeding, anemia, or stroke. The study objective was to evaluate the occurrence of dizziness and/or syncope not related to bleeding, anemia, or stroke in patients treated with direct oral anticoagulants (DOACs).MethodsA retrospective, observational, comparative study of adult patients diagnosed with atrial fibrillation and treated with DOACs was conducted using digital retrieval of medical records. Primary outcomes were an emergency department (ED) visit or hospitalization due to syncope, fall, or dizziness. Cases related to bleeding, anemia, or stroke were excluded. Separate examination of a sample of records validated the data.FindingsOf 6467 eligible patients, 256 (4%) were hospitalized or referred to the ED due to fall, syncope, or dizziness during a mean observation period of 20.1 months. After multivariate regression analysis, statistically independent risk factors were found to be age (hazard ratio [HR] = 1.04, P < 0.0001) and benzodiazepine use (HR = 1.33, P = 0.03). No statistically significant difference was found among the different DOAC types regarding the primary outcome (apixaban and rivaroxaban HR = 0.97, P = 0.85; dabigatran and rivaroxaban HR = 1.2, P = 0.386).ImplicationsThe study results failed to confirm the claimed association between the use of a DOAC and syncopal symptoms unrelated to bleeding, anemia, or stroke in this relatively large Israeli patient population. Age and benzodiazepine treatment were significant independent risk factors of these events.     

New oral anticoagulants in the ED setting: a review

Background

Emergency department (ED) clinicians are not typically involved in the long-term management of patients' anticoagulation therapy, but they are responsible for decision making for emergency conditions requiring anticoagulation, such as acute venous thromboembolism (VTE). In addition, emergency physicians are often faced with patients who present first to the ED with conditions that may prompt long-term anticoagulation upon hospital discharge, such as atrial fibrillation (AF), or who have acute or potential bleeding complications from anticoagulation.

Objective

In this review, clinical trials of new oral anticoagulants evaluated for treatment of VTE and stroke prophylaxis in AF, as well as practical management aspects, will be discussed. In addition, clinical trials evaluating the adjunctive use of the new oral anticoagulants with antiplatelet therapy in patients who have experienced acute coronary syndrome will be explored.

Discussion

Both dabigatran etexilate and rivaroxaban have successfully completed phase III trials for acute VTE treatment and are currently approved for the reduction of risk of stroke and systemic embolism in patients with nonvalvular AF. In a recently completed phase III trial, apixaban also demonstrated promising efficacy and safety in that indication. Rivaroxaban represents the only new anticoagulant to date to have shown promising phase III results as an adjunct to antiplatelet therapy after acute coronary syndrome.

Conclusion

Knowledge of the appropriate clinical use and safety concerns of the new anticoagulants is imperative as they become more frequently prescribed, and their potential uses in the ED setting represent an important aspect of continuing education for emergency physicians.     

Favorable therapeutic index of the direct factor Xa inhibitors, apixaban and rivaroxaban, compared with the thrombin inhibitor dabigatran in rabbits

Summary.  Background: Apixaban is an oral, direct factor Xa (FXa) inhibitor in late-stage clinical development. This study assessed effects of the direct FXa inhibitors, apixaban and rivaroxaban, vs. the direct thrombin inhibitor, dabigatran, on venous thrombosis (VT), bleeding time (BT) and clotting times in rabbits. Methods: We induced the formation of non-occlusive thrombus in VT models by placing threads in the vena cava, and induced bleeding by the incision of cuticles in anesthetized rabbits. Apixaban, rivaroxaban and dabigatran were infused IV to achieve a stable plasma level. Clotting times, including the activated partial thromboplastin time (aPTT), prothrombin time (PT), modified PT (mPT) and thrombin time (TT), were measured. Results: Apixaban, rivaroxaban and dabigatran exhibited dose-related efficacy in preventing VT with EC₅₀ of 65, 33 and 194 n m , respectively. At doses for 80% reduction of control thrombus, apixaban, rivaroxaban and dabigatran prolonged BT by 1.13 ± 0.02-, 1.9 ± 0.1-* and 4.4 ± 0.4-fold*, respectively (* P  <   0.05, vs. apixaban). In the treatment model, these inhibitors equally prevented growth of a preformed thrombus. Antithrombotic doses of apixaban and rivaroxaban prolonged aPTT and PT by <3-fold with no effect on TT. Dabigatran was ≥50-fold more potent in prolonging TT than aPTT and PT. Of the clotting assays studied, apixaban, rivaroxaban and dabigatran responded the best to mPT. Conclusion: Comparable antithrombotic efficacy was observed between apixaban, rivaroxaban and dabigatran in the prevention and treatment of VT in rabbits. Apixaban and rivaroxaban exhibited lower BT compared with dabigatran at equivalent antithrombotic doses. The clinical significance of these findings remains to be determined.     

Management of Factor Xa inhibitor-associated life-threatening major hemorrhage: A retrospective multi-center analysis

Background

Factor Xa (FXa) inhibitors, used for stroke prevention in atrial fibrillation and venous thromboembolism treatment and prevention, are the dominant non-Vitamin K oral anticoagulants on the market. While major bleeding may be less common with these agents compared to warfarin, it is always a risk, and little has been published on the most serious bleeding scenarios. This study describes a cohort of patients with FXa inhibitor-associated life-threatening bleeding events, their clinical characteristics, interventions and outcomes.