Relationship between time in therapeutic range and comparative treatment effect of rivaroxaban and warfarin: results from the ROCKET AF trial

How I use anticoagulation in atrial fibrillation

Atrial fibrillation is the most common cardiac arrhythmia and conveys a significant risk of morbidity and mortality due to related stroke and systemic embolism. Oral anticoagulation (OAC) is the mainstay of thromboembolism prevention, and management of anticoagulation can be challenging. For patients without significant valvular disease, decisions around anticoagulation therapy are first based on the presence of additional stroke risk factors, as measured by the CHA₂DS₂-VASc (congestive heart failure, hypertension, age ≥75, diabetes, prior stroke or transient ischemic attack, vascular disease, age 65-74, and sex category [female]) score. Patients with increased CHA₂DS₂-VASc scores (by regional guidelines) should next be evaluated to determine if they are candidates for non-vitamin K antagonist oral anticoagulant (NOAC) therapy. This should focus on assessment of concomitant valve disease and/or impaired renal function. In eligible patients, the cumulative data support a preference for NOACs over warfarin, as NOACs appear safer and more effective as a group. However, there are no direct, randomized comparisons between NOACs, and therefore, selecting among them can be difficult. In addition, important patient groups remain underrepresented in major clinical trials, and their management is often left to clinician judgment. Data from emerging clinical trials will help guide physicians; however, patient engagement in decisions regarding OAC management will remain vital to ensuring appropriate balance of risks and optimizing health outcomes.

Safety of Non-Vitamin K Antagonist Oral Anticoagulants in Clinical Practice: Focus on Rivaroxaban in Stroke Prevention in Patients With Atrial Fibrillation

Despite direct oral anticoagulants (DOACs) have overcome the most relevant limitations of vitamin K antagonists, many patients with atrial fibrillation are not receiving the appropriate anticoagulant therapy. In addition, when patients are anticoagulated with DOACs, some of them are not taking the dose recommended in the summary of product characteristics. This may be related, at least in part, to the concern about the applicability of findings from randomized clinical trials to real-life patients. In this context, performing studies in daily clinical practice to assess the efficacy and safety of DOACs in real-world setting is mandatory. The aim of this review is to update the current evidence regarding safety of rivaroxaban in clinical practice. 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) showed that rivaroxaban was at least as effective as warfarin for preventing stroke or systemic embolism, with similar rates of major bleeding but with lesser risk of intracranial and fatal bleedings. Data from noninterventional studies and registries have confirmed the good results of ROCKET-AF. Even more, rates of bleeding may be inferior in real-life patients, since they have a lower risk profile than those included in ROCKET-AF.

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.

Direct Oral Anticoagulants for the Management of Thromboembolic Disorders

Anticoagulation therapy is central to the management of thromboembolic disorders, and the use of direct oral anticoagulants offers several advantages over standard therapy with parenteral heparins and vitamin K antagonists. In phase III clinical trials, the direct oral anticoagulants (given once or twice daily) all demonstrated favorable benefit–risk profiles compared with conventional standard therapy for the treatment and secondary prevention of venous thromboembolism and for stroke prevention in patients with nonvalvular atrial fibrillation. In clinical practice, many factors may influence overall clinical outcomes in patients receiving anticoagulant therapy, including adherence and persistence to the prescribed therapy, which becomes particularly important during long-term therapy. When choosing an anticoagulant for an individual patient, the pharmacological and clinical profile of the anticoagulant, its dosing regimen, and the patient’s clinical characteristics (eg, renal function and comorbidities) and preferences should be considered. This review examines the rationale for and clinical evidence of the selected dosing regimens of the direct oral anticoagulants for the treatment of venous thromboembolism and stroke prevention in nonvalvular atrial fibrillation. The potential influence of dosing strategies (eg, once- or twice-daily dosing) and other factors on patient adherence and therapy persistence are also discussed.

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.

Racial Differences in Quality of Anticoagulation Therapy for Atrial Fibrillation (from the TREAT-AF Study)

The influence of race on quality of anticoagulation control is not well described. We examined the association between race, international normalized ratio (INR) monitoring intensity, and INR control in warfarin-treated patients with atrial fibrillation (AF). Using data from the Veterans Health Administration (VHA), we performed a retrospective cohort study of 184,161 patients with a new diagnosis of AF/flutter from 2004 to 2012 who received any VHA prescription within 90 days of diagnosis. The primary predictor was race, ascertained from multiple VHA and linked Medicare demographic files. The primary outcome was first-year and long-term time in therapeutic range (TTR) of INR 2.0 to 3.0. Secondary outcomes were INR monitoring intensity and warfarin persistence. Of the 116,021 patients who received warfarin in the cohort, INR monitoring intensity was similar across racial groups. However, TTR was lowest in blacks and highest in whites (first year 0.49 ± 0.23 vs 0.57 ± 0.21, p <0.001; long term 0.52 ± 0.20 vs 0.59 ± 0.18, p <0.001); 64% of whites and 49% of blacks had long-term TTR >55% (p <0.001). After adjusting for site and patient-level covariates, black race was associated with lower first-year and long-term TTRs (4.2% and 4.1% below the conditional mean, relative to whites; p <0.0001 for both). One-year warfarin persistence was slightly lower in blacks compared to whites (58% vs 60%, p <0.0001). In conclusion, in patients with AF anticoagulated with warfarin, differences in INR control are most evident among blacks, underscoring the need to determine if other types of intensive management or warfarin alternatives may be necessary to improve anticoagulation among vulnerable AF populations.

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.

Antiphospholipid syndrome and anticoagulation quality: a clinical challenge

BACKGROUND AND AIMS

Antiphospholipid Syndrome (APS) is often complicated by ischemic vascular events. Vitamin K Antagonists (VKAs) reduce the risk of recurrent thrombosis. Quality of VKAs treatment, as assessed by the Time in Therapeutic Range (TTR), has never been investigated in APS patients.

METHODS

We performed a prospective observational study including 30 APS and 30 Atrial Fibrillation (AF) patients balanced by age and gender. All patients were treated with VKAs (INR target 2.5), and TTR was calculated.

RESULTS

Median TTR of APS was 53.5% vs. 68% of AF patients (p = 0.001). A multivariable linear regression analysis confirmed that the presence of APS (vs. AF) was independently associated with a worse TTR (B: -14.067, 95% Confidence Interval -25.868/-2.266, p = 0.020). The weekly dosage of VKAs was significantly higher in APS than AF patients.

CONCLUSIONS

APS patients disclose a lower quality of anticoagulation compared to those with AF, requiring higher doses of VKAs. The efficacy of non-vitamin K oral anticoagulants in this high-risk patients should be tested.

Warfarin treatment complications do not correlate to cTTR when above 70

BACKGROUND

The mean time in target range for each centre, cTTR, has previously been shown to correlate to the rate of complications in poorly managed warfarin treatment. However less is known about the correlation when warfarin treatment is well managed.

OBJECTIVES

The aim of this study was to examine the correlation between cTTR and the rate of complications in a real life setting with cTTR above 70%, with focus on patients with warfarin due to atrial fibrillation or secondary prevention of a VTE.

PATIENTS/METHODS

In total 66,605 patients with 89,293 treatment periods, corresponding to 179,624 treatment years, with warfarin treatment due to VTE or AF between January 1st 2006 and December 31th 2011, was retrieved from the national quality register AuriculA. The cohort was matched with the National Patient Register in Sweden for complications and background characteristics.

RESULTS

We found 172 centres and 68,797 treatment periods for AF and 166 centres and 20,496 treatment periods for VTE. Over 90% of the patients had a target range between INR 2-3. We found no correlation between increasing cTTR and reduction in the rate of complications for the AF patients. However, for VTE patients we saw a correlation between increasing cTTR and a reduced complication rate.

CONCLUSIONS

Our results show that at very high cTTR levels, above 70%, further improvements in cTTR do not correlate to less treatment complications at least for patients with AF.

Factor Xa inhibitors: a novel therapeutic class for the treatment of nonvalvular atrial fibrillation

Atrial fibrillation is the most common cause of stroke. Treatment with anticoagulants in patients with atrial fibrillation reduces embolic complications of the disease including stroke. However, the commonly used anticoagulant has a narrow therapeutic index, requires routine monitoring, and has numerous drug and food interactions leading to less than optimal rates of adherence. Inhibition of clotting factor Xa has been evaluated as a potential target for anticoagulation therapy with the hypothesis that using target-specific therapy will alleviate some of the dosing variability observed with the vitamin K antagonist. Three factor Xa inhibitors are currently indicated for use in nonvalvular atrial fibrillation. Similar to the vitamin K antagonist, warfarin, all of the factor Xa inhibitors are administered orally. Rivaroxaban and edoxaban are dosed once daily while apixaban is dosed twice daily. All three agents have demonstrated noninferiority when compared with current standard treatment with warfarin for efficacy and safety outcomes. The therapeutic dose of factor Xa inhibitors vary based on renal function. Unlike warfarin, there are no currently available antidotes for the factor Xa inhibitors although this is an area of interest for current and future studies. In the event of a life-threatening bleed there are established management strategies to reverse the bleeding effects of the factor Xa inhibitors.

Practical and clinical considerations in assessing patients with atrial fibrillation for switching to non-vitamin K antagonist oral anticoagulants in primary care

Atrial fibrillation (AF) is an important risk factor for thromboembolic events, and anticoagulation therapy can reduce this risk. Vitamin K antagonists (VKAs), such as warfarin, have been used for decades in patients with AF for stroke prevention. Currently, non-VKA oral anticoagulants (NOACs) are approved and available for non-valvular AF patients who are at increased risk of stroke. These agents are safe and effective and have important advantages over VKAs, such as significant reduction in intracranial hemorrhage and no need for routine laboratory monitoring. Thus, should all VKA-treated patients be switched to a NOAC? The aims of this article are: 1) to review the advantages of NOACs over VKAs; 2) to identify the group of patients who most benefit from receiving a NOAC and, therefore, are higher priority to be switched from VKAs; and 3) to provide clinical and practical guidance on how to switch patients safely from VKAs to NOACs.

Direct oral anticoagulants in atrial fibrillation: can data from randomized clinical trials be safely transferred to the general population? No

Direct oral anticoagulants (DOAC) represent an innovative and relevant treatment for the prevention of cardiac embolism in patients with atrial fibrillation (AF). Their introduction has been followed by an ample debate on their appropriate use, considering that they can offer an effective treatment for the many patients with AF, which are not taking any effective anticoagulant treatment, even though they have a substantial thromboembolic risk (1). On the other hand, DOAC are much less tested in everyday clinical practice and much more expensive than anti-vitamin k anticoagulants (AVKs). Starting from the quite favorable results of the available randomized controlled trials (RCTs)--showing that DOAC are at least non-inferior to AVK and that may be even better for some outcomes--this article discusses their transferability to the majority of AF patients. In summary, the body of evidence supports the efficacy and safety of DOAC in patients carrying demographic and clinical characteristics similar to subjects included in RCT, but their use in less well-characterized subpopulations requires particular caution, while waiting for more reliable data from the real world.

Stroke and Bleeding Risk Associated With Antithrombotic Therapy for Patients With Nonvalvular Atrial Fibrillation in Clinical Practice

BACKGROUND

The quality of antithrombotic therapy for patients with nonvalvular atrial fibrillation during routine medical care is often suboptimal. Evidence linking stroke and bleeding risk with antithrombotic treatment is limited. The purpose of this study was to evaluate the associations between antithrombotic treatment episodes and outcomes.

METHODS AND RESULTS

A retrospective longitudinal observational cohort study was conducted using patients newly diagnosed with nonvalvular atrial fibrillation with 1 or more stroke risk factors (CHADS2 ≥1) in Kaiser Permanente Southern California between January 1, 2006 and December 31, 2011. A total of 1782 stroke and systemic embolism (SE) and 3528 major bleed events were identified from 23 297 patients during the 60 021 person-years of follow-up. The lowest stroke/SE rates and major bleed rates were observed in warfarin time in therapeutic range (TTR) ≥55% episodes (stroke/SE: 0.87 [0.71 to 1.04]; major bleed: 4.91 [4.53 to 5.28] per 100 person-years), which was similar to the bleed rate in aspirin episodes (4.95 [4.58 to 5.32] per 100 person-years). The warfarin TTR ≥55% episodes were associated with a 77% lower risk of stroke/SE (relative risk=0.23 [0.18 to 0.28]) compared to never on therapy; and the warfarin TTR <55% and on-aspirin episodes were associated with a 20% lower and with a 26% lower risk of stroke/SE compared to never on therapy, respectively. The warfarin TTR <55% episodes were associated with nearly double the risk of a major bleed compared to never on therapy (relative risk=1.93 [1.74 to 2.14]).

CONCLUSIONS

Continuation of antithrombotic therapy as well as maintaining an adequate level of TTR is beneficial to prevent strokes while minimizing bleeding events.

Patients' time in therapeutic range on warfarin among US patients with atrial fibrillation: Results from ORBIT-AF registry

BACKGROUND

Time in therapeutic range (TTR) of international normalized ratio (INR) of 2.0 to 3.0 is important for the safety and effectiveness of warfarin anticoagulation. There are few data on TTR among patients with atrial fibrillation (AF) in community-based clinical practice.

METHODS

Using the US Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF), we examined TTR (using a modified Rosendaal method) among 5,210 patients with AF on warfarin and treated at 155 sites. Patients were grouped into quartiles based on TTR data. Multivariable logistic regression modeling with generalized estimating equations was used to determine patient and provider factors associated with the lowest (worst) TTR.

RESULTS

Overall, 59% of the measured INR values were between 2.0 and 3.0, with an overall mean and median TTR of 65% ± 20% and 68% (interquartile range [IQR] 53%-79%). The median times below and above the therapeutic range were 17% (IQR 8%-29%) and 10% (IQR 3%-19%), respectively. Patients with renal dysfunction, advanced heart failure, frailty, prior valve surgery, and higher risk for bleeding (ATRIA score) or stroke (CHA2DS2-VASc score) had significantly lower TTR (P < .0001 for all). Patients treated at anticoagulation clinics had only slightly higher median TTR (69%) than those not (66%) (P < .0001).

CONCLUSIONS

Among patients with AF in US clinical practices, TTR on warfarin is suboptimal, and those at highest predicted risks for stroke and bleeding were least likely to be in therapeutic range.

Clinical development of rivaroxaban: emerging new clinical evidences?

Rivaroxaban has proven efficacious in a variety of conditions. In fact, rivaroxaban has been approved for the prevention of venous thromboembolism after elective hip or knee replacement surgery, for the prevention and treatment of deep vein thrombosis and pulmonary embolism, for the prevention of stroke in patients with nonvalvular atrial fibrillation and for the prevention of atherothrombotic events after acute coronary syndrome with elevated cardiac biomarkers. However, clinical development of rivaroxaban is ongoing. Considering published and on-going randomized clinical trials, noninterventional studies and registries, over 275,000 patients are being analyzed. The aim of this review was to update the clinical development of rivaroxaban, including completed and ongoing studies not only randomized clinical trials, but also clinical practice studies.

Selection, management, and outcome of vitamin K antagonist-treated patients with atrial fibrillation not switched to novel oral anticoagulants. Results from the Dresden NOAC registry

Atrial fibrillation (AF) patients treated with well-controlled vitamin K antagonists (VKAs) may benefit less from non-vitamin K antagonist oral anticoagulants (NOACs) because they are supposed to be at low risk of thromboembolic and bleeding complications. However, little is known about the selection, management, and outcome of such "stable" VKA patients in current practice. We assessed characteristics, VKA persistence and 12 months' outcome of AF patients selected for VKA continuation. On March 1, 2013, the Dresden NOAC registry opened recruitment of patients continuing on VKA for sites that had been actively recruiting AF patients treated with NOACs in the prior 18 months. Patient characteristics were compared with those of NOAC patients from the same sites. Four hundred twenty-seven VKA patients had a significantly lower bleeding risk profile compared with 706 patients selected for NOAC treatment. For VKA, international normalised ratio time-in-therapeutic range before enrolment was 71 % and increased to 75 % during a mean follow-up of 15 months. Rates of stroke/transient ischaemic attack/systemic embolism were 1.3/100 patient-years (intention-to-treat) and 0.94/100 patient-years (as-treated). On-treatment rate of ISTH major bleeding was 4.15/100 patient-years (95 % CI 2.60-6.29) with a case-fatality rate of 16.3 % (all-cause mortality at day 90 after major bleeding). In conclusion, in daily care, AF patients selected for VKA therapy are healthier than those treated with NOAC, demonstrate a high quality of anticoagulant control and very low stroke rates. However, despite adequate patient selection and INR control, the risk of major VKA bleeding is unacceptably high and bleeding outcome is poor.

Trials of novel oral anticoagulants for stroke prevention in patients with non-valvular atrial fibrillation

Patients with non-valvular atrial fibrillation (AF) face an increased risk of stroke compared with those in normal sinus rhythm. The vitamin K antagonist warfarin, available for over half a century, is highly effective in reducing the risk of stroke in patients with AF, but it is a difficult drug to use properly. As a result, it is challenging to keep the anticoagulant effect of warfarin in the desired range. Newer oral anticoagulants (NOACs) that directly inhibit Factor IIa (thrombin) or Factor Xa provide reliable anticoagulation when administer in fixed oral doses without routine coagulation monitoring. This manuscript will review in detail the pivotal trials of these NOACs that led to their approval as well as comment on the factors that should influence their selection.

Non-vitamin K oral anticoagulants in atrial fibrillation: Where are we now?

Atrial fibrillation (AF) confers increased risk of stroke and other thromboembolic events, and oral anticoagulation therefore is the essential part of AF management to reduce the risk of these complications. Until recently, the vitamin K antagonists (VKAs, e.g., warfarin) were the only oral anticoagulants available, acting by decreased synthesis of vitamin K-dependent coagulation factors (II, VI, IX, and X). The VKAs had many limitations: delayed onset and prolonged offset of action, variability of anticoagulant effect among patients, multiple food and drug interactions affecting pharmacological properties of warfarin, narrow therapeutic window, and obligatory regular laboratory control, which all made warfarin "inconvenient" both for patients and clinicians. The limitations of VKAs led to development of a new class of drugs collectively defined as non-VKA oral anticoagulants (NOACs), which included direct thrombin inhibitors (dabigatran) and factor Xa inhibitors (rivaroxaban, apixaban, and edoxaban). The NOACs avoid many of the VKA drawbacks. In this review, we will focus on the current evidence justifying the use of NOACs in non-valvular AF.

Rationale and Design of Triple AXEL: Trial for Early Anticoagulation in Acute Ischemic Stroke Patients with Nonvalvular Atrial Fibrillation

Rationale

Patients with atrial fibrillation (AF) in the acute stage of ischemic stroke or transient ischemic attack (TIA) are at high risk of recurrent stroke, but the optimal anticoagulation strategy remains unclear due to the concern of intracranial bleeding. Novel oral anticoagulants compared to warfarin might be more safe and efficacious in patients suitable for early anticoagulation.

Aims

This trial is to evaluate the feasibility of early anticoagulation with rivaroxaban in acute ischemic stroke or TIA patients with nonvalvular AF.

Design

This is a randomized, open-label, blinded endpoint evaluation trial. Inclusion criteria are ( 1 ) nonvalvular AF, ( 2 ) presumed cardioembolic stroke or transient ischemic attack (TIA) confirmed by MRI within five-days from onset, and ( 3 ) mild to moderate stroke severity. We will randomize 196 patients to either rivaroxaban (10 mg once daily for five-days followed by 15 mg or 20 mg once daily) or dose-adjusted warfarin (coadministration of aspirin 100 mg per day until achieving international normalized ratio of 1·7). The study is registered in ClinicalTrials.gov (NCT02042534).

Study outcomes

The primary endpoint is the composite of recurrent ischemic lesion and intracranial bleeding on MRI at four-weeks. Secondary endpoints are recurrent ischemic lesions, intracranial bleeding, major bleeding, major vascular events, four-week modified Rankin Scale score, and duration of hospitalization after randomization.

Discussion

The results of this proof-of-concept trial will guide go/no-go decision to a large phase 3 confirmatory trial.

Organ-specific bleeding patterns of anticoagulant therapy: lessons from clinical trials

Anticoagulants are effective at preventing and treating thrombosis, but can cause bleeding. For decades, vitamin K antagonists (VKAs) have been the only available oral anticoagulants. The development of non-VKA oral anticoagulants (NOACs), which inhibit either factor Xa or thrombin stoichiometrically, has provided alternatives to VKAs for several indications. The results of recent large-scale randomised controlled trials comparing NOACs with VKAs for the prevention of stroke in patients with non-valvular atrial fibrillation (AF) have produced some unexpected results. As a group, NOACs showed similar efficacy as warfarin, but a reduced risk of major bleeding. The reduction in bleeding with NOACs was greatest with intracranial hemorrhage. In contrast, the relative risk of gastro-intestinal bleeding was increased with some NOACs. In this review, we explore the potential mechanisms as well as the implications of these organ-specific bleeding patterns.