Dabigatran versus warfarin in patients with mechanical heart valves

Mechanical Versus Bioprosthetic Aortic Valve Replacement in Middle-Aged Adults: A Systematic Review and Meta-Analysis

The choice of a bioprosthetic valve (BV) or mechanical valve (MV) in middle-aged adults undergoing aortic valve replacement is a complex decision that must account for numerous prosthesis and patient factors. A systematic review and meta-analysis was performed to compare long-term survival, major adverse prosthesis-related events, anticoagulant-related events, major bleeding, reoperation, and structural valve degeneration in middle-aged patients receiving a BV or MV. A comprehensive search from six electronic databases was performed from their inception to February 2016. Results from patients aged less than 70 years undergoing aortic valve replacement with a BV or MV were included. There were 12 studies involving 8,661 patients. Baseline characteristics were similar. There was no significant difference in long-term survival among patients aged 50 to 70 or 60 to 70 years. Compared with MVs, BVs had significantly fewer long-term anticoagulant-related events (hazard ratio [HR] 0.54, p = 0.006) and bleeding (HR 0.48, p < 0.00001) but significantly greater major adverse prosthesis-related events (HR 1.82, p = 0.02), including reoperation (HR 2.19, p < 0.00001). The present meta-analysis found no significant difference in survival between BVs and MVs in patients aged 50 to 70 or 60 to 70 years. Compared with MVs, BVs have reduced risk of major bleeding and anticoagulant-related events but increased risk of structural valve degeneration and reoperation. However, the mortality consequences of reoperation appear lower than that of major bleeding, and recent advances may further lower the reoperation rate for BV. Therefore, this review supports the current trend of using BVs in patients more than 60 years of age.

The 2014 Atrial Fibrillation Guidelines Companion: A Practical Approach to the Use of the Canadian Cardiovascular Society Guidelines

The Canadian Cardiovascular Society (CCS) Atrial Fibrillation Guidelines Program has generated a comprehensive series of documents regarding the management of atrial fibrillation (AF) between 2010 and 2014. The guidelines provide evidence-based consensus management recommendations in a broad range of areas. These guidelines have proven useful in informing clinical practice, but often lack detail in specifications related to practical application, particularly for areas in which the evidence base is limited or conflicting. Based on feedback from the community, the CCS Atrial Fibrillation Guidelines Committee has identified a number of areas that require clarification to address commonly asked practical questions related to guidelines application. In the present article a number of such questions are presented and suggestions about how they can be answered are suggested. Among the issues considered are: (1) What duration of AF is clinically significant? (2) How are the risk factors in the CCS Algorithm for selecting anticoagulation therapy derived and defined? (3) How is valvular heart disease defined and how do different forms of valve disease affect the choice of anticoagulant therapy for AF patients? (4) How should we quantify renal dysfunction and how does it affect therapeutic choices? The response to these questions and the underlying logic are provided, along with an indication of future research needed where no specific approach can presently be recommended based on the literature.

Periprocedural antithrombotic therapy during various types of percutaneous cardiovascular interventions

Percutaneous catheter-based interventions became a critically important part of treatment in modern cardiology, improving quality of life as well as saving many life. Due to the introduction of foreign materials to the circulation (either temporarily or permanently) and due to a certain damage to the endothelium or endocardium, the risk of thrombotic complications is substantial and thus some degree of antithrombotic therapy is needed during all these procedures. The intensity (dosage, combination, and duration) of periprocedureal antithrombotic treatment largely varies based on the type of procedure, clinical setting, and comorbidities. This manuscript summarizes the current therapeutic approach to prevent clotting (and bleeding) during a large spectrum of interventions: acute and elective coronary interventions, acute stroke interventions and elective carotid stenting, electrophysiology procedures, interventions for structural heart disease, and peripheral arterial interventions.

Rivaroxaban in the Prevention of Stroke and Systemic Embolism in Patients with Non-Valvular Atrial Fibrillation: Clinical Implications of the ROCKET AF Trial and Its Subanalyses

Atrial fibrillation (AF) is an increasingly common cause of stroke and systemic embolism. While warfarin has been the mainstay of stroke prevention in patients with AF, newer novel oral anticoagulant medications are now available. Rivaroxaban, a direct factor Xa inhibitor with a rapid onset and offset after oral administration, offers potential advantages over warfarin, predominantly due to its predictable pharmacokinetics across wide patient populations. It requires no coagulation monitoring, and only two different doses are needed (20 mg daily for patients with normal renal function and 15 mg daily in those with reduced renal function). A large randomized trial (ROCKET AF) has shown non-inferiority to warfarin for preventing stroke or systemic embolism in the per-protocol population and superiority to warfarin in the on-treatment safety population. Several subanalyses confirm that the treatment effect of rivaroxaban is consistent across different patient subgroups, including those with reduced renal function. The tolerability of rivaroxaban appears similar to that of warfarin, with comparable overall bleeding rates in clinical trials. In ROCKET AF, significantly lower rates of fatal and intracranial bleeding were seen with rivaroxaban, while lower rates of gastrointestinal bleeding were seen with warfarin. Important contraindications to rivaroxaban include valvular AF, the presence of a prosthetic valve (mechanical or bioprosthetic) or valve repair, the need for concurrent dual antiplatelet therapy, and creatinine clearance <30 ml/min. Once-daily dosing and the lack of coagulation monitoring may increase utilization and adherence compared with warfarin, potentially decreasing the large burden of care associated with stroke secondary to AF. Overall, rivaroxaban offers a useful alternative to warfarin for stroke prevention in patients with AF.

Meta-analysis of Randomized Controlled Trials of Genotype-Guided vs Standard Dosing of Warfarin

BACKGROUND

Warfarin is a widely prescribed anticoagulant, and its effect depends on various patient factors including genotypes. Randomized controlled trials (RCTs) comparing genotype-guided dosing (GD) of warfarin with standard dosing have shown mixed efficacy and safety outcomes. We performed a meta-analysis of all published RCTs comparing GD vs standard dosing in adult patients with various indications of warfarin use.

METHODS

We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), and relevant references for English language RCTs (inception through March 2014). We performed the meta-analysis using a random effects model.

RESULTS

Ten RCTs with a total of 2,505 patients were included in the meta-analysis. GD compared with standard dosing resulted in a similar % time in therapeutic range (TTR) at ≤ 1 month follow-up (39.7% vs 40.2%; mean difference [MD], -0.52 [95% CI, -3.15 to 2.10]; P = .70) and higher % TTR (59.4% vs 53%; MD, 6.35 [95% CI, 1.76-10.95]; P = .007) at > 1 month follow-up, a trend toward lower risk of major bleeding (risk ratio, 0.46 [95% CI, 0.19-0.1.11]; P = .08) at ≤ 1 month follow-up and lower risks of major bleeding (0.34 [95% CI, 0.16-0.74], P = .006) at > 1-month follow-up, and shorter time to maintenance dose (TMD) (24.6 days vs 34.1 days; MD, -9.54 days [95% CI, -18.10 to -0.98]; P = .03) at follow-up but had no effects on international normalized ratio [INR] > 4.0, nonmajor bleeding, thrombotic outcomes, or overall mortality.

CONCLUSIONS

In the first month of genotype-guided warfarin therapy, compared with standard dosing, there were no improvements in % TTR, INR > 4.0, major or minor bleeding, thromboembolism, or all-cause mortality. There was a shorter TMD, and, after 1 month, improved % TTR and major bleeding incidence, making this a cost-effective strategy in patients requiring longer anticoagulation therapy.

Management of anticoagulation and antiplatelet therapy in patients with left ventricular assist devices

Left ventricular assist devices (LVADs) have increased the survival of patients with advanced heart failure fourfold. Despite these advances, significant bleeding and thrombotic complications occur. Hemorrhage requiring surgery has been reported in up to 30% of adults and 50% of children after LVAD placement. LVAD thrombosis and embolic stroke lead to significant long-term morbidity. Adults are treated with antithrombotic therapy to prevent thrombotic complications, but the amount and intensity of treatment differs between institutions. The goal international normalized ratio for warfarin therapy varies from 1.5 to 3.0. Some physicians manage adult LVAD patients without antiplatelet medication, whereas other adults are treated with aspirin as a single agent or combined with dipyridamole. In contrast, physicians typically manage children with LVADs using the Edmonton Anticoagulation and Platelet Inhibition Protocol, a detailed algorithm for anticoagulation and antiplatelet treatment modified based on thromboelastography results. LVAD implantation causes consumption of coagulation proteins, activation of fibrinolysis, and loss of high molecular weight von Willebrand protein multimers. How these changes in the coagulation system influence the risk of hemorrhage and initiation of thrombosis is unknown. Prospective, controlled studies are needed to determine the antithrombotic regimen that most effectively balances bleeding and thrombosis in LVAD patients.

Contemporary measures to reduce the risk of embolic events in patients with atrial fibrillation

Atrial fibrillation is a common arrhythmia with significant risk of embolic events. Patients with atrial fibrillation should undergo a careful assessment using validated risk score calculators to estimate the risk of embolic events and the risk of bleeding. Patients deemed to be at a high risk for arterial thromboembolism should be advised to take an oral anticoagulant with a vitamin K antagonist or a target-specific oral anticoagulant unless contraindicated. These agents significantly reduce the risk of embolic events, but at the expense of a higher risk of bleeding. Antiplatelet agents do not confer the same degree of protection and their use should limited. When antithrombotic treatment is contraindicated, novel approaches such as left atrial appendage occlusion should be considered.

Self-Management of Anticoagulant Therapy in Mechanical Heart Valve Patients: A Matched Cohort Study

BACKGROUND

Patient-self-management (PSM) of oral anticoagulant therapy with vitamin K antagonists for mechanical heart valves has demonstrated efficacy in randomized controlled trials. However, the effectiveness of PSM in clinical practice has only been investigated in small trials. Our aim was to evaluate the effectiveness of PSM of oral anticoagulant therapy in mechanical heart valve patients.

METHODS

We conducted a matched cohort study: cases were patients with a mechanical heart valve performing PSM affiliated with Aarhus University Hospital or Aalborg University Hospital, Denmark, in the period 1996 to 2012 (n = 615). Prospectively registered patient data were obtained from databases at two hospitals, and cross linkage between these databases and national patient registries provided detailed information on comorbidities and events. Control patients were matched (on sex, date of birth, year of first valve surgery, and grouped valve position) in a ratio of 5:1 (n = 3,075) with patients receiving conventional management who were randomly selected within the match group. The effectiveness and safety was estimated using major bleeding and thromboembolic events and death as outcomes.

RESULTS

We observed low event rates in the PSM group. After 5 years, PSM was associated with a lower risk of all-cause mortality compared with conventional management (adjusted hazard ratio of 0.49, 95% confidence interval: 0.34 to 0.71). The hazard ratios for thromboembolism and major bleeding were 0.91 (95% confidence interval: 0.66 to 1.24) and 0.83 (95% confidence interval: 0.56 to 1.22).

CONCLUSIONS

Owing to superior clinical effectiveness, self-managed oral anticoagulant therapy may potentially improve the standard of care for patients with mechanical heart valves.

Utilization of Dabigatran for Atrial Fibrillation at 3 Tertiary Care Centres

BACKGROUND

The outpatient management of stroke prevention for patients with atrial fibrillation has recently been published and provides insight into the benefits and risks of the new direct-acting oral anti-coagulants. However, real-world use of these agents for hospital inpatients requires additional study.

OBJECTIVE

To determine prescribing patterns for dabigatran at 3 Canadian hospitals, specifically adherence with the hospitals' prescribing restriction limiting dabigatran to patients with nonvalvular atrial fibrillation and creatinine clearance above 30 mL/min (primary outcome) and assessment of age-related prescribing, prescribing of medications with defined contraindications or potential for interaction when given concurrently with dabigatran, and use of risk stratification tools (secondary outcomes).

METHODS

A retrospective chart review of patients for whom dabigatran was prescribed from August to October 2011 was performed at 3 hospitals in Toronto, Ontario. Descriptive statistics were used for all outcomes assessed.

RESULTS

Overall, dabigatran was prescribed for 69 inpatients, of whom 16 (23%) were new users (dabigatran initiated during hospital admission) and 53 (77%) were prior users (dabigatran prescribed before admission to hospital). Fifty-eight patients (84%; 14 new users and 44 prior users) received dabigatran according to the hospitals' prescribing restriction. For the remaining 11 patients, dabigatran therapy did not meet prescribing restrictions for use because of valvular disease or presence of prosthetic valve (10 patients [14% of the total sample]) and impaired renal function (1 patient [1%]). Among those whose dabigatran therapy met the prescribing restrictions for use, amiodarone and acetylsalicylic acid were the most common concurrently prescribed medications (17 patients [29%] and 14 patients [24%], respectively). Stroke and bleeding risk were documented for only 27 patients (47%) and 10 patients (17%), respectively.

CONCLUSION

At the study hospitals, dabigatran was appropriately prescribed for the indication of nonvalvular atrial fibrillation in patients without renal impairment in most cases. However, greater consideration of cardiac history (including valvular disease and presence of prosthetic valves), drug interactions, and documentation of risks and benefits is warranted. These research findings highlight the importance of and opportunity for pharmacist review and involvement in assessment and selection of patients with indications for anticoagulant therapy, particularly when agents are new to the market.

Initial Experience With Novel Oral Anticoagulants During the First 45 Days After Left Atrial Appendage Closure With the Watchman Device

BACKGROUND

The use of oral anticoagulation or dual antiplatelet therapy (DAPT) is recommended within the first 45 days after left atrial appendage (LAA) closure using the Watchman device because of incomplete device endothelialization. This study reports for the first time the feasibility of novel oral anticoagulants (NOAC) in these patients.

HYPOTHESIS

NOAC therapy is safe and effective after LAA closure.

METHODS

Interventional LAA closure was performed successfully in 45 patients. Of these, 18 patients received NOAC during the first 45 days after implantation and 27 patients received DAPT. Transesophageal echocardiography was conducted 45 days after implantation. The primary study endpoint was abnormal thrombus apposition 45 days after implantation. Secondary study endpoints were death from any cause, major adverse cardiac and cerebrovascular events (MACCE), and major bleedings.

RESULTS

After 45 days, transesophageal echocardiography revealed no abnormal thrombus apposition. During a follow-up of 417 ± 323 days, 7 patients died. No stroke or transient ischemic attack occurred. Nonfatal myocardial infarction occurred in 1 patient. There was a nonsignificant trend for lower all-cause mortality (P = 0.159) and occurrence of MACCE (P = 0.096) in the NOAC group compared with the DAPT group. Overall, 6 patients suffered from a major bleeding (NOAC, n = 3; DAPT, n = 3). In NOAC group, major bleedings (at day 205, 688, and 736) occurred long after termination of NOAC therapy. There was no significant difference in the frequency of major bleedings in different groups.

CONCLUSIONS

Our pilot study suggests that NOAC therapy within the first 45 days after interventional LAA closure is safe and effective.

Dabigatran-Associated Intracranial Hemorrhage: Literature Review and Institutional Experience

Dabigatran etexilate is an oral direct thrombin inhibitor approved for prevention of stroke and systemic embolization in patients with nonvalvular atrial fibrillation and for the treatment of venous thromboembolism. Although dabigatran has a favorable safety profile, predictable pharmacokinetics, fewer drug interactions than warfarin, and does not require monitoring, clinical data regarding dabigatran reversal are limited. In addition, currently available laboratory assays allow measurement of the presence, but not extent, of dabigatran-associated anticoagulation. Patient age, renal function, weight, concurrent drug therapy, adherence, and concomitant disease states can affect dabigatran's efficacy and safety. Management of dabigatran-related intracranial hemorrhage must be approached on a case-by-case basis and include assessment of degree of anticoagulation, severity of hemorrhage, renal function, timing of last dabigatran dose, and risk of thromboembolic events. Initial management includes dabigatran discontinuation and general supportive measures. Oral activated charcoal should be administered in those who ingested dabigatran within 2 hours. Four-factor prothrombin complex concentrates (4PCCs), activated PCC, or recombinant activated factor VII use may be reasonable but is not evidence based. Reserve fresh frozen plasma for patients with dilutional coagulopathy. If readily available, hemodialysis should be considered, particularly in patients with advanced kidney injury or excessive risk of thromboembolic events. More clinical studies are needed to determine a standardized approach to treating dabigatran-associated intracranial hemorrhage. Institutional protocol development will facilitate safe, efficacious, and timely use of the limited management options.

Use Patterns and Unlabeled Uses of Target-Specific Oral Anticoagulants

Background: Target-specific oral anticoagulants (TSOAs) have advantages and disadvantages over warfarin, and they differ by indication, dosage adjustment, and drug interactions. Objective: The purpose of this retrospective cohort study is to determine use patterns and unlabeled uses of TSOAs. Methods: From July 1, 2012, to April 30, 2014, orders for warfarin, dabigatran, rivaroxaban, or apixaban in a tertiary medical center were included. Electronic medical records were reviewed to collect information regarding characteristics of the patients receiving these medications. Unlabeled use was defined as an indication or dose not approved by the US Food and Drug Administration. The percentage of orders for each study drug per month and the percentage of orders for each TSOA that contained an unlabeled use were calculated. Results: Of a total of 869 orders, 140 (16.1%) were for TSOAs (13 dabigatran, 97 rivaroxaban, and 30 apixaban orders). Compared with the first 4 months of the study period, the monthly percentage of orders for a TSOA increased by 2.5-fold in the last 4 months. Of the 3 TSOAs, only orders for dabigatran decreased (5.6% in July 2012 vs 0% in April 2014). Of the 140 TSOA orders, 28 (20.0 %) were unlabeled uses (3 unlabeled indications and 25 unlabeled dose), which included 16 unlabeled renally adjusted doses. The percentage of unlabeled uses did not significantly differ by TSOA. Conclusion: The use of TSOAs has increased and unlabeled uses are common. These data provide opportunities for quality improvement in the use of TSOA in clinical practice.

Potential new uses of non-vitamin K antagonist oral anticoagulants to treat and prevent stroke

BACKGROUND

Non-vitamin K antagonist oral anticoagulant (NOAC) drugs are at least equivalent to warfarin for ischemic stroke prevention in patients with atrial fibrillation and have a lower risk of intracranial hemorrhage. The role of these agents in the prevention and treatment of other types of cerebrovascular disease remains unclear.

METHODS

We reviewed the literature (randomized trials, exploratory comparative studies, and case series) on the use of NOACs in patients with atrial fibrillation, venous thromboembolism, and cerebrovascular disease independent of atrial fibrillation.

RESULTS

The literature on the use of NOACs for treatment and prevention of cerebrovascular disease in patients without atrial fibrillation is sparse. The potential benefit of vitamin K antagonists over antiplatelet agents for primary and secondary prevention in certain subsets of patients with cerebrovascular disease is offset by the increased risk of major and intracranial hemorrhage. Given that NOACs are equivalent to vitamin K antagonists in preventing ischemic stroke and systemic embolism in patients with atrial fibrillation with less bleeding risk, clinical trials are needed to investigate the short- and long-term use of NOACs in populations of patients with other forms of cerebrovascular disease, including those with cryptogenic stroke with or without evidence of patent foramen ovale and low ejection fraction, cervical artery dissection, large artery atherosclerosis, venous thrombosis, and stuttering lacunar stroke.

CONCLUSION

There may be a role for NOACs in stroke prevention and treatment beyond atrial fibrillation. Randomized controlled trials are needed to compare NOACs to current stroke prevention and treatment strategies in certain subgroups of patients with cerebrovascular disease.

Efficacy and safety of novel oral anticoagulants in patients with bioprosthetic valves

PURPOSE

Prosthetic valve replacement is performed in several hundred thousand patients worldwide annually, and many of these patients have or will ultimately develop atrial fibrillation or flutter (AF). Novel oral anticoagulants (NOACs) are not recommended in patients with AF and mechanical valves but have not been evaluated in patients with bioprosthetic valves. This study sought to evaluate the efficacy and safety of NOACs in patients with AF and bioprosthetic valves.

METHODS

A retrospective single-center cohort study was performed on all patients with bioprosthetic valve implantation, for whom a NOAC was prescribed for the indication of AF. Patients were evaluated for thromboembolic events including imaging confirmed ischemic stroke, clinically suspected transient ischemic attack, and major bleeding events (according to International Society on Thrombosis and Hemostasis definition).

RESULTS

In total, 73 patients (26 female, 35.6 %) were identified. NOAC therapy began, on average, 990.0 ± 1029.1 days after bioprosthetic valve implantation for an average duration of 511.8 ± 400.8 days. Aspirin was used concomitantly in a majority of patients (72.6 %). There were no ischemic strokes identified (0.0 %) and one possible TIA (1.4 %). There were 6 (8.2 %) minor and 5 (6.9 %) major bleeding events.

CONCLUSION

The use of NOAC therapy for AF in patients with bioprosthetic valves appears safe and effective in the occurrence of thromboembolic events, however, at the expense of increased bleeding. Larger studies are necessary to confirm these findings.

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

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

Changing practice of anticoagulation: will target-specific anticoagulants replace warfarin?

The target-specific oral anticoagulants are a class of agents that inhibit factor Xa or thrombin. They are effective and safe compared to warfarin for the prevention of stroke and systemic embolism in patients with atrial fibrillation and for the treatment of venous thromboembolism, and they are comparable to low-molecular-weight heparin for thromboprophylaxis after hip or knee arthroplasty. For other indications, however, such as the prevention of stroke in patients with mechanical heart valves, initial studies have been unfavorable for the newer agents, leaving warfarin the anticoagulant of choice. Further studies are needed before the target-specific anticoagulants can be recommended for patients with cancer-associated thrombosis or heparin-induced thrombocytopenia. Concerns also persist about difficulties with the laboratory assessment of anticoagulant effect and the lack of a specific reversal agent. For these reasons, we anticipate that the vitamin K antagonists will continue to be important anticoagulants for years to come.

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.

Misconceptions and Facts About Atrial Fibrillation

Atrial fibrillation is an increasingly common arrhythmia associated with substantial but largely preventable risk of ischemic stroke. There has been an exponential increase in research related to atrial fibrillation in recent years, resulting in some major advances in the therapeutic management. Novel oral anticoagulant agents have become available and require thorough assessment of risk-to-benefit ratio. While the knowledge is rapidly accumulating, the basic principles of atrial fibrillation management remain proper recognition, risk stratification, and appropriate prevention of thromboembolic complications. This review highlights some common misconceptions about atrial fibrillation.

General Medical Considerations for the Wilderness Adventurer: Medical Conditions That May Worsen With or Present Challenges to Coping With Wilderness Exposure

Participation in wilderness and adventure sports is on the rise, and as such, practitioners will see more athletes seeking clearance to participate in these events. The purpose of this article is to describe specific medical conditions that may worsen or present challenges to the athlete in a wilderness environment.

Updated European Heart Rhythm Association Practical Guide on the use of non-vitamin K antagonist anticoagulants in patients with non-valvular atrial fibrillation

The current manuscript is an update of the original Practical Guide, published in June 2013[Heidbuchel H, Verhamme P, Alings M, Antz M, Hacke W, Oldgren J, et al. European Heart Rhythm Association Practical Guide on the use of new oral anticoagulants in patients with non-valvular atrial fibrillation. Europace 2013;15:625-51; Heidbuchel H, Verhamme P, Alings M, Antz M, Hacke W, Oldgren J, et al. EHRA practical guide on the use of new oral anticoagulants in patients with non-valvular atrial fibrillation: executive summary. Eur Heart J 2013;34:2094-106]. Non-vitamin K antagonist oral anticoagulants (NOACs) are an alternative for vitamin K antagonists (VKAs) to prevent stroke in patients with non-valvular atrial fibrillation (AF). Both physicians and patients have to learn how to use these drugs effectively and safely in clinical practice. Many unresolved questions on how to optimally use these drugs in specific clinical situations remain. The European Heart Rhythm Association set out to coordinate a unified way of informing physicians on the use of the different NOACs. A writing group defined what needs to be considered as 'non-valvular AF' and listed 15 topics of concrete clinical scenarios for which practical answers were formulated, based on available evidence. The 15 topics are (i) practical start-up and follow-up scheme for patients on NOACs; (ii) how to measure the anticoagulant effect of NOACs; (iii) drug-drug interactions and pharmacokinetics of NOACs; (iv) switching between anticoagulant regimens; (v) ensuring adherence of NOAC intake; (vi) how to deal with dosing errors; (vii) patients with chronic kidney disease; (viii) what to do if there is a (suspected) overdose without bleeding, or a clotting test is indicating a risk of bleeding?; (xi) management of bleeding complications; (x) patients undergoing a planned surgical intervention or ablation; (xi) patients undergoing an urgent surgical intervention; (xii) patients with AF and coronary artery disease; (xiii) cardioversion in a NOAC-treated patient; (xiv) patients presenting with acute stroke while on NOACs; and (xv) NOACs vs. VKAs in AF patients with a malignancy. Additional information and downloads of the text and anticoagulation cards in >16 languages can be found on an European Heart Rhythm Association web site (www.NOACforAF.eu).

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

Background

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

Methods and Results

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

Conclusions

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

Update on Edoxaban for the Prevention and Treatment of Thromboembolism: Clinical Applications Based on Current Evidence

Vitamin K antagonists (VKA) and heparins have been utilized for the prevention and treatment of thromboembolism (arterial and venous) for decades. Targeting and inhibiting specific coagulation factors have led to new discoveries in the pharmacotherapy of thromboembolism management. These targeted anticoagulants are known as direct oral anticoagulants (DOACs). Two pharmacologically distinct classes of targeted agents are dabigatran etexilate (Direct Thrombin Inhibitor (DTI)) and rivaroxaban, apixaban, and edoxaban (direct oral factor Xa inhibitors (OFXaIs)). Emerging evidence from the clinical trials has shown that DOACs are noninferior to VKA or low-molecular-weight heparins in the prevention and treatment of thromboembolism. This review examines the role of edoxaban, a recently approved OFXaI, in the prevention and treatment of thromboembolism based on the available published literature. The management of edoxaban in the perioperative setting, reversibility in bleeding cases, its role in cancer patients, the relevance of drug-drug interactions, patient satisfaction, financial impacts, and patient education will be discussed.

[Therapy of aortic valve stenosis]

Calcific aortic stenosis is the most frequent valve disorder in the western world. It is a degenerative and chronic progressive disease in the elderly with increasing prevalence due to the demographic development in the population. As there is no medical therapy, the only option in severe aortic stenosis is valve replacement. Echocardiography is the diagnostic tool to assess aortic stenosis severity and morphology of the valve. Aortic stenosis is severe if the valve area is <1.0 cm(2), valve index <0.6 cm(2)/m(2) body surface, mean gradient >40 mmHg, and peak velocity >4.0 m/s. The entity of low flow, low gradient aortic stenosis is complex, and diagnosis and therapy are still challenging. Asymptomatic patients have a good prognosis, but must be reevaluated on a regular basis for the onset of symptoms or signs of progression. If one of the classical symptoms dyspnea and fatigue, angina pectoris or syncope occurs prognosis worsens dramatically and valve replacement is indicated. Gold standard therapy for aortic stenosis is surgical valve replacement. For high-risk patients (older age and severe comorbidities), transcatheter aortic valve implantation (TAVI) is established as standard therapy.

Secondary stroke prevention: challenges and solutions

Stroke is the leading cause of disability in the USA and a major cause of mortality worldwide. One out of four strokes is recurrent. Secondary stroke prevention starts with deciphering the most likely stroke mechanism. In general, one of the main goals in stroke reduction is to control vascular risk factors such as hypertension, diabetes, dyslipidemia, and smoking cessation. Changes in lifestyle like a healthy diet and aerobic exercise are also recommended strategies. In the case of cardioembolism due to atrial fibrillation, mechanical valves, or cardiac thrombus, anticoagulation is the mainstay of therapy. The role of anticoagulation is less evident in the case of bioprosthetic valves, patent foramen ovale, and dilated cardiomyopathy with low ejection fraction. Strokes due to larger artery atherosclerosis account for approximately a third of all strokes. In the case of symptomatic extracranial carotid stenosis, surgical intervention as close as possible in time to the index event seems highly beneficial. In the case of intracranial large artery atherosclerosis, the best medical therapy consists of antiplatelets, high-dose statins, aggressive controls of vascular risk factors, and lifestyle modifications, with no role for intracranial arterial stenting or angioplasty. For patients with small artery occlusion (ie, lacunar stroke), the therapy is similar to that used in patients with intracranial large artery atherosclerosis. Despite the constant new evidence on how to best treat patients who have suffered a stroke, the risk of stroke recurrence remains unacceptably high, thus evidencing the need for novel therapies.

Factor XI and contact activation as targets for antithrombotic therapy

The most commonly used anticoagulants produce therapeutic antithrombotic effects either by inhibiting thrombin or factor Xa (FXa) or by lowering the plasma levels of the precursors of these key enzymes, prothrombin and FX. These drugs do not distinguish between thrombin generation contributing to thrombosis from thrombin generation required for hemostasis. Thus, anticoagulants increase bleeding risk, and many patients who would benefit from therapy go untreated because of comorbidities that place them at unacceptable risk for hemorrhage. Studies in animals demonstrate that components of the plasma contact activation system contribute to experimentally induced thrombosis, despite playing little or no role in hemostasis. Attention has focused on FXII, the zymogen of a protease (FXIIa) that initiates contact activation when blood is exposed to foreign surfaces, and FXI, the zymogen of the protease FXIa, which links contact activation to the thrombin generation mechanism. In the case of FXI, epidemiologic data indicate this protein contributes to stroke and venous thromboembolism, and perhaps myocardial infarction, in humans. A phase 2 trial showing that reduction of FXI may be more effective than low molecular weight heparin at preventing venous thrombosis during knee replacement surgery provides proof of concept for the premise that an antithrombotic effect can be uncoupled from an anticoagulant effect in humans by targeting components of contact activation. Here, we review data on the role of FXI and FXII in thrombosis and results of preclinical and human trials for therapies targeting these proteins.

Oral anticoagulants for stroke prevention in atrial fibrillation: current status, special situations, and unmet needs

In patients with non-valvular atrial fibrillation, oral anticoagulation with vitamin K antagonists reduces the risk of stroke by more than 60%. But vitamin K antagonists have limitations, including causing serious bleeding such as intracranial haemorrhage and the need for anticoagulation monitoring. In part related to these limitations, they are used in only about half of patients who should be treated according to guideline recommendations. In the past decade, oral agents have been developed that directly block the activity of thrombin (factor IIa), as well as drugs that directly inhibit activated factor X (Xa), which is the first protein in the final common pathway to the activation of thrombin. These novel non-vitamin K antagonist oral anticoagulants (NOACs) have been shown to be at least as good as warfarin for stroke prevention in atrial fibrillation and they have proved to have better safety profiles. Their net advantage is underscored by significantly lower all-cause mortality compared with warfarin in large clinical trials. Because of these features and their ease of use, they are recommended for stroke prevention in atrial fibrillation. They have also a fast onset and offset of action, but they currently lack specific antidotes. This paper addresses the role of anticoagulation for stroke prevention in atrial fibrillation in the era of NOACs, with a focus on special situations including management in the event of bleeding and around the time of procedures including cardioversion, catheter ablation, and device implantation. Also their use in patients with concomitant coronary artery disease, with advanced age, with chronic kidney disease, or with valvular heart disease will be discussed as well as the interaction of NOACs with other cardiac medication, and switching between anticoagulants.

Direct-acting oral anticoagulants: pharmacology, indications, management, and future perspectives

In recent years, several direct-acting oral anticoagulants (DOAC) have become available for use in Europe and other regions in indications related to prophylaxis and treatment of venous and arterial thromboembolism. They include the oral direct thrombin inhibitor dabigatran etexilate (Pradaxa, Boehringer Ingelheim) and the oral direct FXa inhibitors rivaroxaban (Xarelto, Bayer HealthCare), apixaban (Eliquis, Bristol-Myers Squibb), and edoxaban (Lixiana/Savaysa, Daiichi-Sankyo). The new compounds have a predictable dose response and few drug-drug interactions (unlike vitamin k antagonists), and they do not require parenteral administration (unlike heparins). However, they accumulate in patients with renal impairment, lack widely available monitoring tests for measuring its anticoagulant activity, and no specific antidotes for neutralization in case of overdose and/or severe bleeding are currently available. In this review, we describe the pharmacology of the DOAC, the efficacy, and safety data from pivotal studies that support their currently approved indications and discuss the postmarketing experience available. We also summarize practical recommendations to ensure an appropriate use of the DOAC according to existing data. Finally, we discuss relevant ongoing studies and future perspectives.

How to define valvular atrial fibrillation?

Atrial fibrillation (AF) confers a substantial risk of stroke. Recent trials comparing vitamin K antagonists (VKAs) with non-vitamin K antagonist oral anticoagulants (NOACs) in AF were performed among patients with so-called "non-valvular" AF. The distinction between "valvular" and "non-valvular" AF remains a matter of debate. Currently, "valvular AF" refers to patients with mitral stenosis or artificial heart valves (and valve repair in North American guidelines only), and should be treated with VKAs. Valvular heart diseases, such as mitral regurgitation, aortic stenosis (AS) and aortic insufficiency, do not result in conditions of low flow in the left atrium, and do not apparently increase the risk of thromboembolism brought by AF. Post-hoc analyses suggest that these conditions probably do not make the thromboembolic risk less responsive to NOACs compared with most forms of "non-valvular" AF. The pathogenesis of thrombosis is probably different for blood coming into contact with a mechanical prosthetic valve compared with what occurs in most other forms of AF. This may explain the results of the only trial performed with a NOAC in patients with a mechanical prosthetic valve (only a few of whom had AF), where warfarin was more effective and safer than dabigatran. By contrast, AF in the presence of a bioprosthetic heart valve or after valve repair appears to have a risk of thromboembolism that is not markedly different from other forms of "non-valvular" AF. Obviously, we should no longer consider the classification of AF as "valvular" (or not) for the purpose of defining the aetiology of the arrhythmia, but for the determination of a different risk of thromboembolic events and the need for a specific antithrombotic strategy. As long as there is no better new term or widely accepted definition, "valvular AF" refers to patients with mitral stenosis or artificial heart valves. Patients with "non-valvular AF" may have other types of valvular heart disease. One should emphasize that "non-valvular AF" does not exclude patients with some types of valvular heart disease from therapy with NOACs.