Phase III studies on novel oral anticoagulants for stroke prevention in atrial fibrillation: a look beyond the excellent results

Efficacy and safety of anticoagulant for treatment and prophylaxis of VTE patients with renal insufficiency: a systemic review and meta-analysis

Patients with venous thromboembolism (VTE) comorbid renal insufficiency (RI) are at higher risk of bleeding and thrombosis. Recommendations in guidelines on anticoagulation therapy for those patients remain ambiguous. The goal of this study is to compare the efficacy and safety between different anticoagulant regimens in VTE patients comorbid RI at different stages of treatment and prophylaxis. We performed English-language searches of Pubmed, EMBASE, and Web of Science (inception to Nov 2022). RCTs evaluated anticoagulants for VTE treatment at the acute phase, extension phase, and prophylaxis in patients with RI and reported efficacy and safety outcomes were selected. The methodological quality of the studies was assessed at the outcome level using the risk-of-bias assessment tool developed by the Cochrane Bias Methods Group. A meta-analysis of twenty-five RCTs was conducted, comprising data from twenty-three articles, encompassing a total of 9,680 participants with RI. In the acute phase, the risk of bleeding was increased with novel oral anticoagulants (NOACs) compared to LMWH (RR 1.29, 95% CI 1.04-1.60). For the prophylaxis of VTE, NOACs were associated with an elevated risk of bleeding compared with placebo (RR 1.31, 95%CI 1.02-1.68). In comparison to non-RI patients, both NOACs and vitamin K antagonists (VKA) could increase the risk of bleeding among RI patients (RR 1.45, 95%CI 1.14-1.84 and RR 1.53, 95%CI 1.25-1.88, respectively) during acute phase, while NOACs may increase the incidence of VTE in RI population (RR 1.74, 95%CI 1.29-2.34). RI patients who are under routine anticoagulation have a significantly higher risk of adverse outcomes. LMWH is the most effective and safe option for VTE treatment or prophylaxis in patients with RI.

Efficacy and Safety of Novel Oral Anticoagulants in Atrial Fibrillation: A Systematic Review

In recent times, novel oral anticoagulants (NOACs)/direct oral anticoagulants (DOACs) have emerged as an alternative to the traditionally used Vitamin K oral antagonists (VKA) like warfarin for the treatment of atrial fibrillation (AF). This systematic review and meta-analysis aims to evaluate the efficacy and safety of NOACs in patients with AF and, thus, the related thromboembolic risks and sequelae. Of the 131 published articles we examined, 11 were included in an in-depth systematic review. The articles we reviewed were from the past ten years, from 2013 onward. The analysis derived the efficacy and safety of NOACs in patients with AF and also included different patients' baseline characteristics and subgroups. This systematic review reiterates previous research findings of superior efficacy and safety of the use of NOACs in the AF population and also illuminates certain head-to-head comparisons of individual NOACs with warfarin. It digressed into subgroups of patients with different baseline characteristics to provide evidence and support the existing guidelines for the use of NOACs in the treatment of AF. Overall, there is marked efficacy and safety of NOACs in patients with AF, be they elderly or Asian, with decreased renal function, or with other comorbidities. Adherence to NOACs was also satisfactory. Despite such a review, there needs to be more research on vast subgroups and also on reversal antidotes like andexanet alfa and idarucizumab, as well as more head-to-head analysis between NOACs over a long duration of study, which would provide more answers and pinpoint reasons as to the differences that exist between demographics and subgroups in the usage of NOACs.

Clinical history and gastrointestinal bleeding in patients taking oral anticoagulants

BACKGROUND

Common risk factors for gastrointestinal bleeding (GIB) are advanced age and the use of antiplatelet or anticoagulants drugs for the prevention of cardiovascular diseases.

METHODS

In this prospective real-world observational study, oral anticoagulated patients were recruited and followed between June 2013 and December 2019. The primary end-point was to evaluate a possible relationship between bleeding events and patients' clinical history of gastrointestinal disease prior to the start of the therapy. The secondary end-points were time of GIB appearance and the percentage of idiopathic or provoked events, i.e., bleeding due to a gastrointestinal disease. In case of GIB event all the patients were studied by means of endoscopic procedures. Cox regression was used to calculate the relative hazard ratios (HRs) of GIB for each considered clinical variable.

RESULTS

734 patients on both VKAs or DOACs were studied. Overall, 46 hemorrhagic events were recorded: 6 were major bleeding (0.42/100 patient-years) while 43 were clinically relevant non major bleeding (2.8/100 patient-years). The Cox regression analysis did not show any relationships among GIB and the variables considered.

CONCLUSION

The patients' clinical history is neither a predictor for GIB bleeding nor a guide to the choice of the oral anticoagulant to be administered. Routinely applying bleeding risk screening, such as occult blood in the stool, should be added to the periodic laboratory checks for early recognition of patients at higher risk of GIB.

[Spontaneous intraocular hemorrhage under oral anticoagulation : Apixaban in comparison to phenprocoumon]

BACKGROUND

To determine and compare the frequency of intraocular hemorrhage in patients who underwent oral anticoagulation with apixaban or phenprocoumon.

METHODS

A retrospective analysis of patients under oral anticoagulant medication (apixaban or phenprocoumon) seen between January 2015 and June 2015 at the department of ophthalmology, University of Muenster Medical Center was performed. Vitreal or retinal hemorrhage in addition to clinical information including age, gender, best corrected visual acuity, concomitant diseases, concomitant medication and therapy were obtained. Bleeding frequency in both groups was compared using Fisher's exact test.

RESULTS

A total of 172 patients were included with a mean age = 74.0 ± 10.6 years, 57.0% (n = 98) male and 43.0% (n = 74) female. In the phenprocoumon group 147 patients (3.4%, n = 5) developed a retinal or vitreal hemorrhage. In the apxiban group 25 patients (36%, n = 9) developed a retinal or vitreal hemorrhage. There was a significant correlation between the group and bleeding risk (p < 0.001).

CONCLUSION

There was a significant correlation between medication (apixaban vs. phenprocoumon) and bleeding risk in this study population. Further studies with more patients especially in patients with a high risk of hemorhage, age-related macular degeneration (AMD) and proliferative diabetic retinopathy are needed.

A Renal Function Based Trade-Off Analysis of Non-vitamin K Antagonist Oral Anticoagulants in Nonvalvular Atrial Fibrillation

Background: Non-vitamin K antagonist oral anticoagulants (NOACs) depend on some degree of renal excretion, and no head-to-head comparisons based on renal function is available. This study mainly investigated the trade-off property of NOACs in nonvalvular atrial fibrillation (NVAF) with varying degrees of renal function.

Methods: A comprehensive search of Medline, Embase, Cochrane Library, and Clinical Trials.gov Website was performed for eligible randomized controlled trials (RCTs) that reported the efficacy and safety outcomes according to renal function of NOACs. Primary efficacy outcome was any Stroke or systemic embolism (S/SE). Major bleeding was considered as a primary safety outcome. Risk ratios (RRs) with their confidence intervals (CIs), the surface under the cumulative ranking curve (SUCRA), and trade-off analysis were conducted by renal function.

Results: Finally, 5 phase III Clinical Trials (72961 NVAF patients) comparing NOACs with warfarin in NVAF patients were included. In terms of normal renal function, dabigatran-150 mg was ranked first for efficacy (SUCRA: 90.3), and edoxaban-30 mg was ranked first for safety (SUCRA: 93.3). Dabigatran-110 mg/150 mg, and apixaban-5 mg were regarded as the most effective and reasonably safe interventions in the trade-off analysis. Regarding mild renal impairment, edoxaban-60 mg was ranked first for efficacy (SUCRA: 97.8), and edoxaban-30 mg was ranked first for safety (SUCRA: 99.5). Edoxaban-60 mg and dabigatran-150 mg were accounted as the most effective and reasonably safe interventions. With regards to moderate renal impairment, dabigatran-150 mg was ranked first for efficacy (SUCRA: 95.1), and edoxaban-15 mg was ranked first for safety (SUCRA: 98.2). Apixaban-2.5 mg and Edoxaban-30 mg was considered as the reasonably effective and the safest interventions.

Conclusions: Dabigatran-150 mg seems the most effective therapy in patients with normal renal function and moderate renal impairment, and edoxaban-60 mg in patients with mild renal impairment. Low dose edoxaban (15 and 30 mg) seems the safest intervention. Apixaban-2.5 mg and edoxaban-30 mg might be the best trade-off property in moderate renal insufficiency.

HIGHLIGHTS 

STUDY REGISTRATION: 

PROSPERO Identifier, CRD42017054235.

Phenotyping of CYP 4501A2 Activity by Total Overnight Salivary Caffeine Assessment (TOSCA) in Patients on Warfarin Treatment: A Cross-Sectional Study

Warfarin is an oral anticoagulant, commonly used for primary and secondary prevention of venous and arterial thromboembolic events. The drug is characterized by narrow therapeutic index, widespread individual variability in clinical response, and high rates of adverse events, particularly bleeding complications. For these reasons, a close monitoring of the dosage, using the frequent assessment of coagulation status by means of International Normalized Ratio value, is mandatory. Warfarin is metabolized by hepatic cytochrome P-450. High CYP 450 activity may lead to low drug concentration and requires high warfarin doses to reach efficacy; conversely, low CYP 450 activity is responsible for high drug concentration and needs for low doses to avoid potential toxicity risks. The major isoforms of CYP involved in the metabolism of warfarin sodium are CYP1A2 (for the R-warfarin) and CYP2C9 (for the S-warfarin). The probes for testing CYP1A2 are phenacetin and caffeine while for CYP2C9 tolbutamide. Although S-warfarin has major activity, it was decided to exclude its phenotyping for ethical issues, being mandatory to use a drug (tolbutamide). Instead, it was chosen to test the 1A2 isoform, as the activity of the latter isoform could be investigated by using caffeine contained in the caffeinated beverages. Specifically, a single-point concentration of salivary caffeine (total overnight salivary caffeine assessment [TOSCA]) after an overnight period of the caffeinated beverages abstinence was utilized. In the present study, 75 nonsmoker patients regularly receiving warfarin sodium were enrolled. The results have showed a significant association of the warfarin dose with TOSCA values (coefficient = -0.15, standard error = 0.04, 95% confidence interval = -0.24 to -0.06, t = -3.23, P = .002). In conclusion, the phenotyping of CYP1A2 by TOSCA could be useful, if further proven, to help manage patients on warfarin in order to lessen severe adverse events.

Chronic kidney disease and anticoagulation: from vitamin K antagonists and heparins to direct oral anticoagulant agents

Anticoagulation in patients with impaired kidney function can be challenging since drugs' pharmacokinetics and bioavailability are altered in this setting. Patients with chronic kidney disease (CKD) treated with conventional anticoagulant agents [vitamin K antagonist (VKA), low-molecular weight heparin (LMWH) or unfractionated heparin (UFH)] are at high risk of bleeding events (both non-major and major clinically relevant bleeding). While anticoagulation reduces the risk of thromboembolic events, the co-existing bleeding risk and the fact that the most commonly used anticoagulation agents are eliminated via the kidneys pose additional challenges. More recently, two classes of direct oral anticoagulant agents (DOACs) have been investigated for the prevention and management of venous thromboembolic events: the direct factor Xa inhibitors rivaroxaban, apixaban and edoxaban, and the direct thrombin inhibitor dabigatran. In this review, we discuss the complex challenges and the practical considerations associated with the management of anticoagulation treatment in patients with CKD, with a special focus on DOACs.

The perioperative management of new direct oral anticoagulants: a question without answers

New direct oral anticoagulant agents (DOAC) are currently licensed for thromboprophylaxis after hip and knee arthroplasty and for longterm prevention of thromboembolic events in non-valvular atrial fibrillation as well as treatment and secondary prophylaxis of venous thromboembolism. Some other medical indications are emerging. Thus, anaesthesiologists are increasingly likely to encounter patients on these drugs who need elective or emergency surgery. Due to the lack of experience and data, the management of DOAC in the perioperative period is controversial. In this article, we review available information and recommendations regarding the periprocedural management of the currently most clinically developed DOAC, apixaban, dabigatran, and rivaroxaban. We discuss two trends of managing patients on DOAC for elective surgery. The first is stopping the DOAC 1–5 days before surgery (depending on the drug, patient and bleeding risk) without bridging. The second is stopping the DOAC 5 days preoperatively and bridging with low-molecular-weight heparin. The management of patients on DOAC needing emergency surgery is also reviewed. As no data exist for the use of haemostatic products for the reversal of the anticoagulant effect in these cases, rescue treatment recommendations are proposed.

Point-of-care testing INR: an overview

Oral anticoagulant therapies with the anti-vitamin K drugs (AVK), warfarin, acenocoumarol and phenprocoumon, are employed in primary and secondary anti-thrombotic prophylaxis in patients with venous thromboembolism, atrial fibrillation and cardiac mechanical valves. However, a monitoring test such as the International Normalized Ratio (INR) is required. The periodic monitoring of this therapy entails discomfort for the patients. Telemedicine and telecare can provide significant aid in the management of this therapy allowing patients to perform the test at home or anywhere else with a portable device, i.e. point-of-care testing (POCT), and to send the result to a thrombosis (TC) via web. Patients can receive dose adjustment sent back by the TC. The effectiveness of this type of management is equal or superior to the traditional AVK monitoring in terms of hemorrhagic and thrombotic events. Analysis of the costs with a horizon of 10 years reveals that both self-testing and self-management are cost-effective. The aim of this overview is to describe the pros and cons of the use of POCT as an alternative in the monitoring of AVK. In particular, description of the POCT, decentralization, quality of the therapy, safety and costs will be examined.

Novel oral anticoagulants for the secondary prevention of cerebral ischemia: a network meta-analysis

BACKGROUND

Novel oral anticoagulants (NOACs) have shown to be both safe and effective for ischemic stroke prevention in patients with nonvalvular atrial fibrillation (NVAF). We conducted a network meta-analysis (NMA) using published data from secondary prevention subgroups of different phase III randomized clinical trials (RCTs) comparing individual NOACs with warfarin.

METHODS

Eligible studies were identified by searching MEDLINE and SCOPUS and the Cochrane Central Register of Controlled Trials databases. First, we conducted a pairwise meta-analysis for each pairwise comparison, and then we performed NMA to combine direct and indirect evidence for any given pair of treatments. The comparative effects of all NOACs against warfarin were ranked with the surface under the cumulative ranking (SUCRA) curve for each outcome.

RESULTS

We identified four RCTs (including 15,240 patients) comparing individual NOACs (apixaban, dabigatran, rivaroxaban) with warfarin. Using indirect evidence, dabigatran was related to a significantly lower risk of hemorrhagic stroke compared with rivaroxaban [risk ratio (RR) 0.28; 95% confidence interval (CI) 0.11-0.75], while rivaroxaban was associated with a significantly lower risk of major gastrointestinal bleeding compared with dabigatran (RR 0.14; 95% CI 0.03-0.74). We also performed clustered ranking plot for the primary efficacy and safety endpoints to identify the treatment with the probably best benefit-to-risk ratio profile.

CONCLUSIONS

The three NOACs showed differences in terms of safety and efficacy for secondary stroke prevention in NVAF. Our findings can serve only as hypothesis generation and require independent confirmation in head-to-head RCTs, owing to the sparse available evidence and increased uncertainty in both indirect effect estimates and ranking of treatments.

Non-VKA Oral Anticoagulants: Accurate Measurement of Plasma Drug Concentrations

Non-VKA oral anticoagulants (NOACs) have now widely reached the lucrative market of anticoagulation. While the marketing authorization holders claimed that no routine monitoring is required and that these compounds can be given at fixed doses, several evidences arisen from the literature tend to demonstrate the opposite. New data suggests that an assessment of the response at the individual level could improve the benefit-risk ratio of at least dabigatran. Information regarding the association of rivaroxaban and apixaban exposure and the bleeding risk is available in the drug approval package on the FDA website. These reviews suggest that accumulation of these compounds increases the risk of experiencing a bleeding complication. Therefore, in certain patient populations such as patients with acute or chronic renal impairment or with multiple drug interactions, measurement of drug exposure may be useful to ensure an optimal treatment response. More specific circumstances such as patients experiencing a haemorrhagic or thromboembolic event during the treatment duration, patients who require urgent surgery or an invasive procedure, or patient with a suspected overdose could benefit from such a measurement. This paper aims at providing guidance on how to best estimate the intensity of anticoagulation using laboratory assays in daily practice.

Current state of anticoagulants to treat deep venous thrombosis

Anticoagulation remains the cornerstone of treatment in patients with deep vein thrombosis (DVT). While parenteral anticoagulants and oral vitamin K antagonists (e.g., warfarin) have been used for many decades, the recent development of novel oral anticoagulants have provided clinicians with an expanding set of therapeutic options for DVT. This review summarizes the pharmacology and clinical trial results of these new oral anticoagulants. Several practical considerations to the use of these oral anticoagulants including issues related to adherence, monitoring, and reversal are also discussed.

Comparison of idrabiotaparinux with vitamin K antagonists for prevention of thromboembolism in patients with atrial fibrillation: the Borealis-Atrial Fibrillation Study

BACKGROUND

Idrabiotaparinux, a long-acting inhibitor of factor Xa, was shown to be effective in the treatment of patients with venous thromboembolism.

OBJECTIVE

To assess non-inferiority for the efficacy of idrabiotaparinux versus warfarin in patients with atrial fibrillation (AF) at risk of stroke and systemic embolism. Bleeding was also assessed.

METHODS

This randomized, double-blind trial enrolled patients with electrocardiogram-documented AF. Idrabiotaparinux was administered weekly via subcutaneous injection, and warfarin was administered daily with dose adjustment to maintain the international normalized ratio between 2.0 and 3.0. Each idrabiotaparinux injection was 3 mg for the first 7 weeks, followed by 2 mg thereafter, except in patients with a creatinine clearance of 30-50 mL min(-1) or aged ≥ 75 years. The patients received 1.5 mg after the first 7 weeks. The efficacy outcome was the composite of all fatal or non-fatal strokes and systemic embolism. The safety outcome was clinically relevant bleeding (major and clinically relevant non-major bleeding).

RESULTS

The study was terminated prematurely by the sponsor for strategic/commercial, not scientific, reasons, with 39% of the planned number of patients included and an average duration of treatment of 240 days. Of the 1886 idrabiotaparinux recipients, 20 developed stroke or systemic embolism (1.5% per year), whereas this occurred in 22 of the 1887 warfarin patients (1.6% per year, hazard ratio 0.98, 95% confidence interval 0.49-1.66). The annual incidence of bleeding was 6.1% in the idrabiotaparinux and 10.0% in the warfarin group (hazard ratio 0.61, 95% confidence interval 0.46-0.81).

CONCLUSION

If anything, despite its early termination, the idrabiotaparinux regimen studied suggested a comparable efficacy to dose-adjusted warfarin, with a lower bleeding risk.

Management of anticoagulant-related intracranial hemorrhage: an evidence-based review

The increased use of anticoagulants for the prevention and treatment of thromboembolic diseases has led to a rising incidence of anticoagulant-related intracranial hemorrhage (AICH) in the aging western population. High mortality accompanies this form of hemorrhagic stroke, and significant and debilitating long-term consequences plague survivors. Although management guidelines for such hemorrhages are available for the older generation anticoagulants, they are still lacking for newer agents, which are becoming popular among physicians. Supportive care, including blood pressure control, and reversal of anticoagulation remain the cornerstone of acute management of AICH. Prothrombin complex concentrates are gaining popularity over fresh frozen plasma, and reversal agents for newer anticoagulation agents are being developed. Surgical interventions are options fraught with complications, and are decided on a case-by-case basis. Our current state of understanding of this condition and its management is insufficient. This deficit calls for more population-based studies and therapeutic trials to better evaluate risk factors for, and to prevent and treat AICH.

Improved accuracy of anticoagulant dose prediction using a pharmacogenetic and artificial neural network-based method

BACKGROUND

The unpredictability of acenocoumarol dose needed to achieve target blood thinning level remains a challenge. We aimed to apply and compare a pharmacogenetic least-squares model (LSM) and artificial neural network (ANN) models for predictions of acenocoumarol dosing.

METHODS

LSM and ANN models were used to analyze previously collected data on 174 participants (mean age: 67.45 SD 13.49 years) on acenocoumarol maintenance therapy. The models were based on demographics, lifestyle habits, concomitant diseases, medication intake, target INR, and genotyping results for CYP2C9 and VKORC1. LSM versus ANN performance comparisons were done by two methods: by randomly splitting the data as 50 % derivation and 50 % validation cohort followed by a bootstrap of 200 iterations, and by a 10-fold leave-one-out cross-validation technique.

RESULTS

The ANN-based pharmacogenetic model provided higher accuracy and larger R value than all other LSM-based models. The accuracy percentage improvement ranged between 5 % and 24 % for the derivation cohort and between 12 % and 25 % for the validation cohort. The increase in R value ranged between 6 % and 31 % for the derivation cohort and between 2 % and 31 % for the validation cohort. ANN increased the percentage of accurately dosed subjects (mean absolute error ≤1 mg/week) by 14.1 %, reduced the percentage of mis-dosed subjects (mean absolute error 2-3 mg/week) by 7.04 %, and reduced the percentage of grossly mis-dosed subjects (mean absolute error ≥4 mg/week) by 24 %.

CONCLUSIONS

ANN-based pharmacogenetic guidance of acenocoumarol dosing reduces the error in dosing to achieve target INR. These results need to be ascertained in a prospective study.

Use of new oral anticoagulants in antiphospholipid syndrome

The current mainstay of treatment of thrombotic APS is long-term anticoagulation with oral vitamin K antagonists (VKA) such as warfarin. However, the use of warfarin is problematic, particularly in patients with antiphospholipid syndrome (APS). The new oral anticoagulants (NOAC) include dabigatran etexilate (Pradaxa®), a direct thrombin inhibitor, and rivaroxaban (Xarelto®), Apixaban (Eliquis) and Edoxaban (Lixiana®), which are direct anti-Xa inhibitors. Unlike warfarin, these agents do not interact with dietary constituents and alcohol, have few reported drug interactions, and monitoring of their anticoagulant intensity is not routinely required due to their predictable anticoagulant effects. In this chapter, we discuss clinical and laboratory aspects of NOAC. These agents have been approved for several therapeutic indications based on phase III prospective randomised controlled clinical trials using warfarin at a target INR of 2.5 (i.e. range 2.0-3.0) as the comparator. However these trials may not be directly applicable to patients with antiphospholipid syndrome (APS) where prospective clinical studies of NOAC are the way forward.

Investigational anticoagulants for hematological conditions: a new generation of therapies

INTRODUCTION

The introduction of novel anticoagulants has had contrasting effects on the agents in the pipeline, fueling the development of some and sinking the others. The complexity of the coagulation cascade offers interesting inhibition choices that might become valid treatment options.

AREAS COVERED

This review will highlight some of the anticoagulants in the pipeline. Following the success of the direct thrombin and FXa inhibitors already in the market, new agents are being tested. These include AZD0837, betrixaban, letaxaban, darexaban, and LY517717. Targeting other components of the hemostatic pathway might lead to better safety profiles without influencing efficacy. Inhibitors to FVIIa-tissue factor (FVIIa/TF) complex, FIX, FXI, and FXII are being assessed. New inspiring inhibitors are antisense oligonucleotides (ASOs) and aptamers. These are highly specific agents with readily reversible effect and might be engineered to inhibit any coagulation factor. Currently tested ASOs and aptamers are inhibitors of FXI, FXII, thrombin, FIXa, and platelet GPIV.

EXPERT OPINION

Some of the agents in the pipeline offer valid treatment option for long-term therapy, overcoming some of the drawbacks of the novel anticoagulants. Research is being driven by an expanding market in the anticoagulation field that has been unexploited for a long time.

Improving the use of direct oral anticoagulants in atrial fibrillation

The need for anticoagulation in patients with atrial fibrillation (AF), and the inherent limitations of warfarin have fostered the search for direct oral anticoagulant drugs (DOACs). In recent years, inhibitors of thrombin (Dabigatran etexilate) and of activated factor X (Rivaroxaban, Apixaban) have become clinically available, and current guidelines of the European Society of Cardiology recommend their use in AF patients. However, limitations and uncertainties as to their clinical handling have emerged. With the exception of those on Dabigatran, caution is presently recommended in patients undergoing ablation for AF, and in those who need dual antiplatelet treatment and/or invasive procedures. The use of DOACs is precluded in patients with (mechanical) heart valves, severe kidney or liver failure, malignancy, in those on prasugrel or ticagrelor, in those with the need for coronary stenting, and in naive patients with AF who need cardioversion. Moreover it must be borne in mind that limited long-term efficacy and safety data are available and that adherence of patients to DOACs may be a major issue in the real-life setting. The definition and type of monitoring to be employed to evaluate adherence to DOACs is lacking, nor have we practical guidelines on how to handle bleeding in patients on DOACs. Finally, ad hoc validated definitions of therapeutic failures are crucial in cost/utility analyses, but these are not available for DOACs. Thus, caution, vigilance and further clinical data are mandatory for a safe and appropriate use of DOACs as alternatives to warfarin in AF patients in real-life clinical settings.

Thromboprophylaxis in the oldest old with atrial fibrillation: between Scylla and Charybdis

Within a few decades half of the patients with non-valvular atrial fibrillation (AF) will be older than 80 years. These patients are at particularly high risk of thromboembolism (Scylla) but also of the hemorrhagic complications of thromboprophylaxis (Charybdis). A frequent compromise is to use as antithrombotic agents instead of vitamin-K antagonists aspirin or other antiplatelet drugs, which are ineffective for thromboprophylaxis in the oldest old and definitely not free from a high risk of severe bleeding. All the new direct anticoagulants currently licensed (dabigatran, rivaroxaban, apixaban) are at least as effective as warfarin for thromboprophylaxis in AF, but the risk of the intracranial bleeding, the most feared complication of anticoagulant therapy, is at least halved. In the oldest patients of 80 years of age or more preliminary data, available so far only for dabigatran, indicate that the favorable outcomes of direct anticoagulants are also present in this subgroup, often left untreated for fear of intracranial bleeding. The choice between the different direct anticoagulants is driven by the presence or not of renal insufficiency, the presence and degree of multimorbidity and polypharmacy and by the likelihood or not of poor treatment adherence in patients who are often frail and with some degree of cognitive impairment.

New oral anticoagulants in atrial fibrillation: a reappraisal of trial results looking at absolute figures

Three new oral anticoagulant agents were tested versus warfarin in separate, large phase III randomized clinical trials for prevention of any stroke and systemic embolism in atrial fibrillation. Dabigatran, a direct thrombin inhibitor, is at 110 mg bid non-inferior and at 150 mg bid superior to warfarin; rivaroxaban, a factor X inhibitor, is also non-inferior, and apixaban, also a factor X inhibitor, is superior to warfarin on the same efficacy end point. Statistical analysis of subgroups does not suggest, for any of the tested drugs, major differences in relation to different risk levels and history of previous stroke/TIA. This re-appraisal of data was undertaken in search for possible additional information, by considering the absolute differences in efficacy and safety events versus warfarin and the corresponding efficiency and number needed to treat, also with regard to secondary versus primary prevention. By this approach, it appears that for all drugs, equivalence or advantage versus warfarin on the efficacy end point is largely driven by a reduction in hemorrhagic rather than ischemic strokes. Dabigatran shows a balanced effect on ischemic and hemorrhagic strokes, and apixaban is most effective in sparing intracranial bleeding versus warfarin. In secondary prevention, better efficiency is shown by dabigatran 150 and apixaban, versus rivaroxaban, despite the higher proportion of post-stroke/TIA patients (55 %) in the ROCKET AF trial of rivaroxaban seemed to favor better results of this drug in secondary prevention. These and other results of our approach should not be directly translated into clinical practice. They may supply useful suggestions to be subsequently tested in specific trials, although head-to-head comparative studies of the three drugs remain unlikely.