Primary prevention of arterial thromboembolism in non-rheumatic atrial fibrillation in primary care: randomised controlled trial comparing two intensities of coumarin with aspirin

Estimating Vitamin K Antagonist Anticoagulation Benefit in People With Atrial Fibrillation Accounting for Competing Risks: Evidence From 12 Randomized Trials

BACKGROUND

Patients with atrial fibrillation have a high mortality rate that is only partially attributable to vascular outcomes. The competing risk of death may affect the expected anticoagulant benefit. We determined if competing risks materially affect the guideline-endorsed estimate of anticoagulant benefit.

METHODS

We conducted a secondary analysis of 12 randomized controlled trials that randomized patients with atrial fibrillation to vitamin K antagonists (VKAs) or either placebo or antiplatelets. For each participant, we estimated the absolute risk reduction (ARR) of VKAs to prevent stroke or systemic embolism using 2 methods-first using a guideline-endorsed model (CHA2DS2-VASc) and then again using a competing risk model that uses the same inputs as CHA2DS2-VASc but accounts for the competing risk of death and allows for nonlinear growth in benefit. We compared the absolute and relative differences in estimated benefit and whether the differences varied by life expectancy.

RESULTS

A total of 7933 participants (median age, 73 years, 36% women) had a median life expectancy of 8 years (interquartile range, 6-12), determined by comorbidity-adjusted life tables and 43% were randomized to VKAs. The CHA2DS2-VASc model estimated a larger ARR than the competing risk model (median ARR at 3 years, 6.9% [interquartile range, 4.7%-10.0%] versus 5.2% [interquartile range, 3.5%-7.4%]; P<0.001). ARR differences varied by life expectancies: for those with life expectancies in the highest decile, 3-year ARR difference (CHA2DS2-VASc model - competing risk model 3-year risk) was -1.3% (95% CI, -1.3% to -1.2%); for those with life expectancies in the lowest decile, 3-year ARR difference was 4.7% (95% CI, 4.5%-5.0%).

CONCLUSIONS

VKA anticoagulants were exceptionally effective at reducing stroke risk. However, VKA benefits were misestimated with CHA2DS2-VASc, which does not account for the competing risk of death nor decelerating treatment benefit over time. Overestimation was most pronounced when life expectancy was low and when the benefit was estimated over a multiyear horizon.

Overestimation of anticoagulant benefit in patients with atrial fibrillation and low life expectancy: evidence from 12 randomized trials

Background

Patients with atrial fibrillation (AF) have a high rate of all-cause mortality that is only partially attributable to vascular outcomes. While the competing risk of death may affect expected anticoagulant benefit, guidelines do not account for it. We sought to determine if using a competing risks framework materially affects the guideline-endorsed estimate of absolute risk reduction attributable to anticoagulants.

Methods

We conducted a secondary analysis of 12 RCTs that randomized patients with AF to oral anticoagulants or either placebo or antiplatelets. For each participant, we estimated the absolute risk reduction (ARR) of anticoagulants to prevent stroke or systemic embolism using two methods. First, we estimated the ARR using a guideline-endorsed model (CHA ₂ DS ₂ -VASc) and then again using a Competing Risk Model that uses the same inputs as CHA ₂ DS ₂ -VASc but accounts for the competing risk of death and allows for non-linear growth in benefit over time. We compared the absolute and relative differences in estimated benefit and whether the differences in estimated benefit varied by life expectancy.

Results

7933 participants had a median life expectancy of 8 years (IQR 6, 12), determined by comorbidity-adjusted life tables. 43% were randomized to oral anticoagulation (median age 73 years, 36% women). The guideline-endorsed CHA ₂ DS ₂ -VASc model estimated a larger ARR than the Competing Risk Model (median ARR at 3 years, 6.9% vs. 5.2%). ARR differences varied by life expectancies: for those with life expectancies in the highest decile, 3-year ARR difference (CHA ₂ DS ₂ -VASc model - Competing Risk Model 3-year risk) was -1.2% (42% relative underestimation); for those with life expectancies in the lowest decile, 3-year ARR difference was 5.9% (91% relative overestimation).

Conclusion

Anticoagulants were exceptionally effective at reduced stroke risk. However, anticoagulant benefits were misestimated with CHA ₂ DS ₂ -VASc, which does not account for the competing risk of death nor decelerating treatment benefit over time. Overestimation was most pronounced in patients with the lowest life expectancy and when benefit was estimated over a multi-year horizon.

Association of Oral Anticoagulation With Stroke in Atrial Fibrillation or Heart Failure: A Comparative Meta-Analysis

Background and Purpose

Atrial fibrillation and heart failure with reduced ejection fraction (HFrEF) are common sources of cardioembolism. While oral anticoagulation is strongly recommended for atrial fibrillation, there are marked variations in guideline recommendations for HFrEF due to uncertainty about net clinical benefit. This systematic review and meta-analysis evaluates the comparative association of oral anticoagulation with stroke and other cardiovascular risk in populations with atrial fibrillation or HFrEF in sinus rhythm and identify factors mediating different estimates of net clinical benefit.

Methods

PubMed and Embase were searched from database inception to November 20, 2019 for randomized clinical trials comparing oral anticoagulation to control. A random-effects meta-analysis was used to estimate a pooled treatment-effect overall and within atrial fibrillation and HFrEF trials. Differences in treatment effect were assessed by estimating I2 among all trials and testing the between-trial-population P-interaction. The primary outcome measure was all stroke. Secondary outcome measures were ischemic stroke, hemorrhagic stroke, mortality, myocardial infarction, and major hemorrhage.

Results

Twenty-one trials were eligible for inclusion, 15 (n=19 332) in atrial fibrillation (mean follow-up: 23.1 months), and 6 (n=9866) in HFrEF (mean follow-up: 23.9 months). There were differences in primary outcomes between trial populations, with all-cause mortality included for 95.2% of HFrEF trial population versus 0.38% for atrial fibrillation. Mortality was higher in controls groups of HFrEF populations (19.0% versus 9.6%) but rates of stroke lower (3.1% versus 7.0%) compared with atrial fibrillation. The association of oral anticoagulation with all stroke was consistent for atrial fibrillation (odds ratio, 0.51 [95% CI, 0.42–0.63]) and HFrEF (odds ratio, 0.61 [95% CI, 0.47–0.79]; I2=12.4%; P interaction=0.31). There were no statistically significant differences in the association of oral anticoagulation with cardiovascular events, mortality or bleeding between populations.

Conclusions

The relative association of oral anticoagulation with stroke risk, and other cardiovascular outcomes, is similar for patients with atrial fibrillation and HFrEF. Differences in the primary outcomes employed by trials in HFrEF, compared with atrial fibrillation, may have contributed to differing conclusions of the relative efficacy of oral anticoagulation.

Risk analysis of new oral anticoagulants for gastrointestinal bleeding and intracranial hemorrhage in atrial fibrillation patients: a systematic review and network meta-analysis

BACKGROUND

Antithrombotic therapy using new oral anticoagulants (NOACs) in patients with atrial fibrillation (AF) has been generally shown to have a favorable risk-benefit profile. Since there has been dispute about the risks of gastrointestinal bleeding (GIB) and intracranial hemorrhage (ICH), we sought to conduct a systematic review and network meta-analysis using Bayesian inference to analyze the risks of GIB and ICH in AF patients taking NOACs.

METHODS

We analyzed data from 20 randomized controlled trials of 91 671 AF patients receiving anticoagulants, antiplatelet drugs, or placebo. Bayesian network meta-analysis of two different evidence networks was performed using a binomial likelihood model, based on a network in which different agents (and doses) were treated as separate nodes. Odds ratios (ORs) and 95% confidence intervals (CIs) were modeled using Markov chain Monte Carlo methods.

RESULTS

Indirect comparisons with the Bayesian model confirmed that aspirin+clopidogrel significantly increased the risk of GIB in AF patients compared to the placebo (OR 0.33, 95% CI 0.01-0.92). Warfarin was identified as greatly increasing the risk of ICH compared to edoxaban 30 mg (OR 3.42, 95% CI 1.22-7.24) and dabigatran 110 mg (OR 3.56, 95% CI 1.10-8.45). We further ranked the NOACs for the lowest risk of GIB (apixaban 5 mg) and ICH (apixaban 5 mg, dabigatran 110 mg, and edoxaban 30 mg).

CONCLUSIONS

Bayesian network meta-analysis of treatment of non-valvular AF patients with anticoagulants suggested that NOACs do not increase risks of GIB and/or ICH, compared to each other.

Oral anticoagulants for primary prevention, treatment and secondary prevention of venous thromboembolic disease, and for prevention of stroke in atrial fibrillation: systematic review, network meta-analysis and cost-effectiveness analysis

BACKGROUND

Warfarin is effective for stroke prevention in atrial fibrillation (AF), but anticoagulation is underused in clinical care. The risk of venous thromboembolic disease during hospitalisation can be reduced by low-molecular-weight heparin (LMWH): warfarin is the most frequently prescribed anticoagulant for treatment and secondary prevention of venous thromboembolism (VTE). Warfarin-related bleeding is a major reason for hospitalisation for adverse drug effects. Warfarin is cheap but therapeutic monitoring increases treatment costs. Novel oral anticoagulants (NOACs) have more rapid onset and offset of action than warfarin, and more predictable dosing requirements.

OBJECTIVE

To determine the best oral anticoagulant/s for prevention of stroke in AF and for primary prevention, treatment and secondary prevention of VTE.

DESIGN

Four systematic reviews, network meta-analyses (NMAs) and cost-effectiveness analyses (CEAs) of randomised controlled trials.

SETTING

Hospital (VTE primary prevention and acute treatment) and primary care/anticoagulation clinics (AF and VTE secondary prevention).

PARTICIPANTS

Patients eligible for anticoagulation with warfarin (stroke prevention in AF, acute treatment or secondary prevention of VTE) or LMWH (primary prevention of VTE).

INTERVENTIONS

NOACs, warfarin and LMWH, together with other interventions (antiplatelet therapy, placebo) evaluated in the evidence network.

MAIN OUTCOME MEASURES

Efficacy Stroke, symptomatic VTE, symptomatic deep-vein thrombosis and symptomatic pulmonary embolism. Safety Major bleeding, clinically relevant bleeding and intracranial haemorrhage. We also considered myocardial infarction and all-cause mortality and evaluated cost-effectiveness.

DATA SOURCES

MEDLINE and PREMEDLINE In-Process & Other Non-Indexed Citations, EMBASE and The Cochrane Library, reference lists of published NMAs and trial registries. We searched MEDLINE and PREMEDLINE In-Process & Other Non-Indexed Citations, EMBASE and The Cochrane Library. The stroke prevention in AF review search was run on the 12 March 2014 and updated on 15 September 2014, and covered the period 2010 to September 2014. The search for the three reviews in VTE was run on the 19 March 2014, updated on 15 September 2014, and covered the period 2008 to September 2014.

REVIEW METHODS

Two reviewers screened search results, extracted and checked data, and assessed risk of bias. For each outcome we conducted standard meta-analysis and NMA. We evaluated cost-effectiveness using discrete-time Markov models.

RESULTS

Apixaban (Eliquis^®, Bristol-Myers Squibb, USA; Pfizer, USA) [5 mg bd (twice daily)] was ranked as among the best interventions for stroke prevention in AF, and had the highest expected net benefit. Edoxaban (Lixiana^®, Daiichi Sankyo, Japan) [60 mg od (once daily)] was ranked second for major bleeding and all-cause mortality. Neither the clinical effectiveness analysis nor the CEA provided strong evidence that NOACs should replace postoperative LMWH in primary prevention of VTE. For acute treatment and secondary prevention of VTE, we found little evidence that NOACs offer an efficacy advantage over warfarin, but the risk of bleeding complications was lower for some NOACs than for warfarin. For a willingness-to-pay threshold of > £5000, apixaban (5 mg bd) had the highest expected net benefit for acute treatment of VTE. Aspirin or no pharmacotherapy were likely to be the most cost-effective interventions for secondary prevention of VTE: our results suggest that it is not cost-effective to prescribe NOACs or warfarin for this indication.

CONCLUSIONS

NOACs have advantages over warfarin in patients with AF, but we found no strong evidence that they should replace warfarin or LMWH in primary prevention, treatment or secondary prevention of VTE.

LIMITATIONS

These relate mainly to shortfalls in the primary data: in particular, there were no head-to-head comparisons between different NOAC drugs.

FUTURE WORK

Calculating the expected value of sample information to clarify whether or not it would be justifiable to fund one or more head-to-head trials.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013005324, CRD42013005331 and CRD42013005330.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Feline Cardiogenic Arterial Thromboembolism: Prevention and Therapy

Feline cardiogenic arterial thromboembolism (CATE) is a devastating disease whereby 33% of cats survive their initial event, although approximately 50% of mortality is from euthanasia. Short-term management focuses on inducing a hypocoagulable state, improving blood flow, and providing supportive care. Ideally, all cats should be given 72 hours of treatment to determine the acute clinical course. Preventive protocols include antiplatelet and/or anticoagulant drugs, with the only prospective clinical trial demonstrating that clopidogrel is superior to aspirin with a lower CATE recurrence rate and longer time to recurrent CATE. Newer anticoagulant drugs hold great promise in the future of managing this disease.

Cost-Effectiveness of Percutaneous Closure of the Left Atrial Appendage in Atrial Fibrillation Based on Results From PROTECT AF Versus PREVAIL

BACKGROUND

Randomized trials of left atrial appendage (LAA) closure with the Watchman device have shown varying results, and its cost effectiveness compared with anticoagulation has not been evaluated using all available contemporary trial data.

METHODS AND RESULTS

We used a Markov decision model to estimate lifetime quality-adjusted survival, costs, and cost effectiveness of LAA closure with Watchman, compared directly with warfarin and indirectly with dabigatran, using data from the long-term (mean 3.8 year) follow-up of Percutaneous Closure of the Left Atrial Appendage Versus Warfarin Therapy for Prevention of Stroke in Patients With Atrial Fibrillation (PROTECT AF) and Prospective Randomized Evaluation of the Watchman LAA Closure Device in Patients With Atrial Fibrillation (PREVAIL) randomized trials. Using data from PROTECT AF, the incremental cost-effectiveness ratios compared with warfarin and dabigatran were $20 486 and $23 422 per quality-adjusted life year, respectively. Using data from PREVAIL, LAA closure was dominated by warfarin and dabigatran, meaning that it was less effective (8.44, 8.54, and 8.59 quality-adjusted life years, respectively) and more costly. At a willingness-to-pay threshold of $50 000 per quality-adjusted life year, LAA closure was cost effective 90% and 9% of the time under PROTECT AF and PREVAIL assumptions, respectively. These results were sensitive to the rates of ischemic stroke and intracranial hemorrhage for LAA closure and medical anticoagulation.

CONCLUSIONS

Using data from the PROTECT AF trial, LAA closure with the Watchman device was cost effective; using PREVAIL trial data, Watchman was more costly and less effective than warfarin and dabigatran. PROTECT AF enrolled more patients and has substantially longer follow-up time, allowing greater statistical certainty with the cost-effectiveness results. However, longer-term trial results and postmarketing surveillance of major adverse events will be vital to determining the value of the Watchman in clinical practice.

The Efficacy and Safety of 3 Types of Interventions for Stroke Prevention in Patients With Cardiovascular and Cerebrovascular Diseases: A Network Meta-analysis

PURPOSE

The goal of this study was to compare the relative efficacy and safety of different types of interventions for stroke prevention in patients with cardiovascular and cerebrovascular diseases.

METHODS

This network meta-analysis (NMA) was conducted with a random effects model of Bayesian framework using Stata version 12.0. Odds ratios (ORs) and their credible intervals (CrIs) were applied for the efficacy and safety evaluation of various medical interventions, including aspirin, dipyridamole, ticlopidine, warfarin, and apixaban. In addition, the ranking of probability of every clinical outcome was estimated by comparing the surface under the cumulative ranking curve.

FINDINGS

Compared with dabigatran, both edoxaban and aspirin + warfarin exhibited a higher rate of all-cause stroke (OR, 2.84 [95% CrI, 1.17-6.97]; OR, 3.42 [95% CrI, 1.20-9.84]). With respect to intracranial hemorrhage, aspirin + clopidogrel yielded worse outcomes than 7 treatments, including placebo, apixaban, aspirin, aspirin + dipyridamole, cilostazol, clopidogrel, and dabigatran (OR, 2.21 [95% CrI, 1.45-3.40]; OR, 2.11 [95% CrI, 1.05-4.17]; OR, 1.53 [95% CrI, 1.11-2.15]; OR, 1.78 [95% CrI, 1.01-3.03]; OR, 4.17 [95% CrI, 1.37-14.28]; OR, 1.85 [95% CrI, 1.22-2.86]; and OR, 2.56 [95% CrI, 1.37-4.76]). In terms of ischemic stroke, dabigatran provided better efficacy than placebo, aspirin, and aspirin + dipyridamole (OR, 0.36 [95% CrI, 0.18-0.72]; OR, 0.43 [95% CrI, 0.21-0.84]; and OR, 0.41 [95% CrI, 0.17-0.94]). As for mortality, dabigatran resulted in a lower mortality compared with aspirin, aspirin + clopidogrel, edoxaban, and warfarin (OR, 0.48 [95% CrI, 0.23-0.97]; OR, 0.40 [95% CrI, 0.17-0.92]; OR, 0.27 [95% CrI, 0.10-0.72]; and OR, 0.52 [95% CrI, 0.28-0.92]).

IMPLICATIONS

There are still some limitations to our NMA research. For instance, the lack of direct evidence for some therapies resulted in inconsistencies, particularly for warfarin compared with placebo and clopidogrel under different end points. Moreover, the included randomized controlled trials for patients with cardiovascular and cerebrovascular diseases are relatively broad, involving atrial fibrillation, myocardial infarction, and large-artery atherosclerosis stroke. Although further research is needed, dabigatran is highly recommended based on the present NAM for the treatment of cardiovascular and cerebrovascular diseases due to the drug's efficacy and safety.

Exploratory Network Meta Regression Analysis of Stroke Prevention in Atrial Fibrillation Fails to Identify Any Interactions with Treatment Effect

Background

Patients with atrial fibrillation are at a greater risk of stroke and therefore the main goal for treatment of patients with atrial fibrillation is to prevent stroke from occurring. There are a number of different stroke prevention treatments available to include warfarin and novel oral anticoagulants. Previous network meta-analyses of novel oral anticoagulants for stroke prevention in atrial fibrillation acknowledge the limitation of heterogeneity across the included trials but have not explored the impact of potentially important treatment modifying covariates.

Objectives

To explore potentially important treatment modifying covariates using network meta-regression analyses for stroke prevention in atrial fibrillation.

Methods

We performed a network meta-analysis for the outcome of ischaemic stroke and conducted an exploratory regression analysis considering potentially important treatment modifying covariates. These covariates included the proportion of patients with a previous stroke, proportion of males, mean age, the duration of study follow-up and the patients underlying risk of ischaemic stroke.

Results

None of the covariates explored impacted relative treatment effects relative to placebo. Notably, the exploration of ‘study follow-up’ as a covariate supported the assumption that difference in trial durations is unimportant in this indication despite the variation across trials in the network.

Conclusion

This study is limited by the quantity of data available. Further investigation is warranted, and, as justifying further trials may be difficult, it would be desirable to obtain individual patient level data (IPD) to facilitate an effort to relate treatment effects to IPD covariates in order to investigate heterogeneity. Observational data could also be examined to establish if there are potential trends elsewhere. The approach and methods presented have potentially wide applications within any indication as to highlight the potential benefit of extending decision problems to include additional comparators outside of those of primary interest to allow for the exploration of heterogeneity.

Comparative Effectiveness of Interventions for Stroke Prevention in Atrial Fibrillation: A Network Meta-Analysis

BACKGROUND

The goal of this study was to compare the safety and effectiveness of individual antiembolic interventions in nonvalvular atrial fibrillation (AF): novel oral anticoagulants (NOACs) (apixaban, dabigatran, edoxaban, and rivaroxaban); vitamin K antagonists (VKA); aspirin; and the Watchman device.

METHODS AND RESULTS

A network meta-analysis of randomized, clinical trials (RCTs) was performed. RCTs that included patients with prosthetic cardiac valves or mitral stenosis, mean or median follow-up <6 months, <200 participants, without published report in English language, and NOAC phase II studies were excluded. The placebo/control arm received either placebo or no treatment. The primary efficacy outcome was the combination of stroke (of any type) and systemic embolism. All-cause mortality served as a secondary efficacy outcome. The primary safety outcome was the combination of major extracranial bleeding and intracranial hemorrhage. A total of 21 RCTs (96 017 nonvalvular AF patients; median age, 72 years; 65% males; median follow-up, 1.7 years) were included. In comparison to placebo/control, use of aspirin (odds ratio [OR], 0.75 [95% CI, 0.60-0.95]), VKA (0.38 [0.29-0.49]), apixaban (0.31 [0.22-0.45]), dabigatran (0.29 [0.20-0.43]), edoxaban (0.38 [0.26-0.54]), rivaroxaban (0.27 [0.18-0.42]), and the Watchman device (0.36 [0.16-0.80]) significantly reduced the risk of any stroke or systemic embolism in nonvalvular AF patients, as well as all-cause mortality (aspirin: OR, 0.82 [0.68-0.99]; VKA: 0.69 [0.57-0.85]; apixaban: 0.62 [0.50-0.78]; dabigatran: 0.62 [0.50-0.78]; edoxaban: 0.62 [0.50-0.77]; rivaroxaban: 0.58 [0.44-0.77]; and the Watchman device: 0.47 [0.25-0.88]). Apixaban (0.89 [0.80-0.99]), dabigatran (0.90 [0.82-0.99]), and edoxaban (0.89 [0.82-0.96]) reduced risk of all-cause death as compared to VKA.

CONCLUSIONS

The entire spectrum of therapy to prevent thromboembolism in nonvalvular AF significantly reduced stroke/systemic embolism events and mortality.

Preventing bleeding and thromboembolic complications in atrial fibrillation patients undergoing surgery

Neurologists feel uneasy when asked about temporary anticoagulant interruption for surgery in patients with atrial fibrillation (AF). Rational decisions can be made based on current scientific evidence. Method Critical review of international guidelines and selected references pertaining to bleeding and thromboembolism during periods of oral anticoagulant interruption. Results Withholding oral anticoagulants leads to an increased risk of perioperative thromboembolism, depending on factors such as age, renal and liver function, previous ischemic events, heart failure etc. Surgeries are associated with a variable risk of bleeding - from minimal to very high. Individualized decisions about preoperative drug suspension, bridging therapy with heparin and time to restart oral anticoagulants after hemostasis can significantly reduce these opposing risks. Conclusion Rational decisions can be made after discussion with all Health care team professionals involved and consideration of patient fears and expectations. Formal written protocols should help managing antithrombotic treatment during this delicate period.

Aspirin Compared to Low Intensity Anticoagulation in Patients with Non-Valvular Atrial Fibrillation. A Systematic Review and Meta-Analysis

Background

Despite its lack of efficacy, aspirin is commonly used for stroke prevention in atrial fibrillation. Since prior studies have suggested a benefit of low-intensity anticoagulation over aspirin in the prevention of vascular events, the aim of this systematic review was to compare the outcomes of patients with non-valvular atrial fibrillation treated with low-intensity anticoagulation with Vitamin K antagonists or aspirin.

Methods

We conducted a systematic review searching Ovid MEDLINE, Embase and the Cochrane Central Register of Controlled Trials, from 1946 to October 14^th, 2015. Randomized controlled trials were included if they reported the outcomes of patients with non-valvular atrial fibrillation treated with a low-intensity anticoagulation compared to patients treated with aspirin. The primary outcome was a combination of ischemic stroke or systemic embolism. The random-effects model odds ratio was used as the outcome measure.

Results

Our initial search identified 6309relevant articles of which three satisfied our inclusion criteria and were included. Compared to low-intensity anticoagulation, aspirin alone did not reduce the incidence of ischemic stroke or systemic embolism OR 0.94 (95% CI 0.57–1.56), major bleeding OR 1.06 (95% CI 0.42–2.62) or vascular death OR 1.04 (95% CI 0.61–1.75). The use of aspirin was associated with a significant increase in all-cause mortality OR 1.66 (95% CI 1.12–2.48).

Conclusion

In patients with non-valvular atrial fibrillation, aspirin provides no benefits over low-intensity anticoagulation. Furthermore, the use of aspirin appears to be associated with an increased risk in all-cause mortality. Our study provides more evidence against the use aspirin in patients with non-valvular atrial fibrillation.

Clinical and Safety Outcomes of Oral Antithrombotics for Stroke Prevention in Atrial Fibrillation: A Systematic Review and Network Meta-analysis

INTRODUCTION

Novel oral anticoagulants (NOACs) expanded the options for stroke prevention in atrial fibrillation (AF). Earlier studies comparing their relative effectiveness and safety typically do not incorporate age-related differences or postmarketing studies. This study aimed to summarize and compare clinical and safety outcomes of oral antithrombotics for stroke prevention in AF in younger (65-74 years) and older (≥75 years) elderly.

METHODS

We searched PubMed, Embase, and The Cochrane Library from inception through May 1, 2015, for randomized and nonrandomized studies comparing NOACs, warfarin, and aspirin in elderly with AF. Stroke and systemic embolism (SSE) and major bleeding (MB) are the main outcomes. We also studied secondary outcomes of ischemic stroke, all-cause mortality, intracranial bleeding, and gastrointestinal bleeding.

RESULTS

Of 5255 publications identified, 25 randomized controlled trials and 24 nonrandomized studies of 897,748 patients were included. NOACs reduced the risk of SSE compared with warfarin (rate ratios [RRs] range from 0.78-0.82). Relative to SSE, NOACs demonstrated a smaller benefit for ischemic stroke (dabigatran 110 mg, RR 1.08; edoxaban, 1.00; apixaban, 0.99). On the contrary, aspirin was associated with a significantly higher risk of SSE, ischemic stroke, and mortality than warfarin or NOACs (RR > 1), particularly in older elderly. Regarding safety, medium-dose aspirin (100-300 mg daily) and aspirin/clopidogrel combination showed an increased risk of MB compared with warfarin (RR 1.17 and 1.15, respectively), as per dabigatran 150 mg and rivaroxaban in older elderly (RR 1.17 and 1.12, respectively). Among the NOACs, dabigatran 150 mg conferred greater gastrointestinal bleeding risk compared with warfarin (RR 1.51), whereas rivaroxaban (RR 0.73) demonstrated less benefit of reduced intracranial bleeding than other NOACs (RRs range 0.39-0.46).

CONCLUSIONS

Lower rates of SSE and intracranial bleeding were observed with the NOACs compared with warfarin. Dabigatran 150 mg and rivaroxaban were associated with higher rates of MB in older elderly.

Efficacy and safety of oral anticoagulants versus aspirin for patients with atrial fibrillation: a meta-analysis

The purpose of this study was to perform a meta-analysis comparing the effectiveness and safety of anticoagulation to antiplatelet therapy for the prevention of thromboembolic events in patients with atrial fibrillation (AF). MEDLINE, Cochrane, EMBASE, and Google Scholar databases were searched for studies published through May 31, 2014. Randomized controlled trials comparing anticoagulants (warfarin) and antiplatelet therapy in patients with AF were included. The primary outcomes were the rates of stroke and systemic embolism. Secondary outcomes included the rates of hemorrhage/major bleeding and death. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Nine reports of 8 trials that enrolled 4363 patients (2169 patients received anticoagulation and 2194 antiplatelet therapy) were included. All of the studies compared adjusted-dose warfarin or with aspirin, and the majority of the patients were >70 years of age. Anticoagulants were titrated to an international normalized ratio (INR) of 2.0 to 4.5, and aspirin was administered at a dosage of 75 to 325 mg/d. Death occurred in 206 participants treated with an anticoagulant and 229 participants treated with antiplatelet therapy. There was no significant difference in the overall stroke rate between the groups (OR = 0.667, 95% CI 0.426-1.045, P = 0.08); however, patients with nonrheumatic AF (NRAF) treated with an anticoagulant had a lower risk of stroke (OR = 0.557, 95% CI 0.411-0.753, P < 0.001). Anticoagulants were associated with a lower risk of embolism (OR = 0.616, 95% CI = 0.392-0.966, P = 0.04), and this finding persisted in patients with NRAF (OR = 0.581, 95% CI 0.359-0.941, P = 0.03). No significant difference in the rate of hemorrhage/major bleeding was noted (OR = 1.497, 95% CI 0.730-3.070, P = 0.27), and this finding persisted on subgroup analysis. Anticoagulants appear to be more effective than aspirin in preventing embolisms in patients with AF, as the risk of bleeding is not increased.

Quality of vitamin K antagonist control and outcomes in atrial fibrillation patients: a meta-analysis and meta-regression

BACKGROUND

Atrial fibrillation (AF) patients frequently require anticoagulation with vitamin K antagonists (VKAs) to prevent thromboembolic events, but their use increases the risk of hemorrhage. We evaluated time spent in therapeutic range (TTR), proportion of international normalized ratio (INR) measurements in range (PINRR), adverse events in relation to INR, and predictors of INR control in AF patients using VKAs.

METHODS

We searched MEDLINE, CENTRAL and EMBASE (1990-June 2013) for studies of AF patients receiving adjusted-dose VKAs that reported INR control measures (TTR and PINRR) and/or reported an INR measurement coinciding with thromboembolic or hemorrhagic events. Random-effects meta-analyses and meta-regression were performed.

RESULTS

Ninety-five articles were included. Sixty-eight VKA-treated study groups reported measures of INR control, while 43 studies reported an INR around the time of the adverse event. Patients spent 61% (95% CI, 59-62%), 25% (95% CI, 23-27%) and 14% (95% CI, 13-15%) of their time within, below or above the therapeutic range. PINRR assessments were within, below, and above range 56% (95% CI, 53-59%), 26% (95% CI, 23-29%) and 13% (95% CI, 11-17%) of the time. Patients receiving VKA management in the community spent less TTR than those managed by anticoagulation clinics or in randomized trials. Patients newly receiving VKAs spent less TTR than those with prior VKA use. Patients in Europe/United Kingdom spent more TTR than patients in North America. Fifty-seven percent (95% CI, 50-64%) of thromboembolic events and 42% (95% CI, 35 - 51%) of hemorrhagic events occurred at an INR <2.0 and >3.0, respectively; while 56% (95% CI, 48-64%) of ischemic strokes and 45% of intracranial hemorrhages (95% CI, 29-63%) occurred at INRs <2.0 and >3.0, respectively.

CONCLUSIONS

Patients on VKAs for AF frequently have INRs outside the therapeutic range. While, thromboembolic and hemorrhagic events do occur patients with a therapeutic INR; patients with an INR <2.0 make up many of the cases of thromboembolism, while those >3.0 make up many of the cases of hemorrhage. Managing anticoagulation outside of a clinical trial or anticoagulation clinic is associated with poorer INR control, as is, the initiation of therapy in the VKA-naïve. Patients in Europe/UK have better INR control than those in North America.

Comparison of CHADS2 and CHA2DS2-VASC anticoagulation recommendations: evaluation in a cohort of atrial fibrillation ablation patients

Aims

Atrial fibrillation (AF) is associated with a high incidence of strokes/thromboembolism. The CHADS₂ score assigns points for several clinical variables to identify stroke risk. The CHA₂DS₂-VAS_C score uses the same variables but also incorporates age 65 to 74, female gender, and vascular disease in an effort to provide a more refined risk of stroke/thromboembolism. We aimed to examine oral anticoagulation (OAC) recommendations for a cohort of patients undergoing AF ablation depending upon whether thrombo-embolic risk was determined by the CHADS₂ or CHA₂DS₂-VAS_C score.

Methods and results

For 1411 patients we compared OAC recommendations for each of these risk stratification schemes to one of the three OAC strategies: (i) NO-OAC, (ii) CONSIDER-OAC, and (iii) DEFINITE-OAC. Compared with the CHADS₂ score, the CHA₂DS₂-VAS_C score reduced NO-OAC from 40.3 to 21.8% and CONSIDER-OAC from 36.6 to 27.9% while increasing DEFINITE-OAC from 23.0 to 50.2% of patients. Age 65 to 74 and female gender accounted for 95.2% and vascular disease for only 4.8% of recommendations for more aggressive OAC using CHA₂DS₂-VAS_C. Most vascular disease occurred in patients with higher CHADS₂ scores already recommended for DEFINITE-OAC (P < 0.0001). Reclassifying 30 females of age <65 with a CHA₂DS₂-VAS_C score of 1 to the NO-OAC group had minimal effect on the overall recommendations.

Conclusion

Compared with the CHADS₂ score, in our AF ablation population, the CHA₂DS₂-VAS_C score markedly increases the number of AF patients for whom OAC is recommended. It will be important to determine by randomized trials if this major paradigm shift to greater use of OAC using the CHA₂DS₂-VAS_C scoring improves patient outcomes.

Current and new oral antithrombotics in non-valvular atrial fibrillation: a network meta-analysis of 79 808 patients

BACKGROUND

Antithrombotic therapy reduces stroke, embolism and mortality in patients with atrial fibrillation (AF); however, meta-analyses have focused on pairwise comparisons of treatments.

OBJECTIVE

To synthesise the evidence from trials using a multiple treatment comparison methods thereby permitting a broader comparison across multiple therapies.

DESIGN, SETTING, PATIENTS

Randomised controlled trials in patients with AF of antithrombotics were identified from MEDLINE, Embase, and Cochrane Central Register of Controlled Trials through May 2012. We performed a random-effects model within a Bayesian framework using Markov Chain Monte Carlo simulation to calculate pooled OR and 95% credibility intervals (CrI). We also ranked therapies by their likelihood of leading to the best results for the outcomes.

MAIN OUTCOME MEASURE

Multiple endpoints including stroke, embolism, death and bleeding.

RESULTS

We identified 20 studies with 79 808 patients allocated to 8 treatments: ASA, ASA plus clopidogrel, vitamin K antagonists (VKAs), dabigatran 110 mg, dabigatran 150 mg, rivaroxaban, apixaban or placebo/control. Compared with placebo/control, dabigatran 150 mg was associated with the lowest risk of stroke (OR=0.25, 0.15-0.43), the composite of ischaemic stroke or systemic embolism (OR=0.26, 0.12-0.54) and mortality (OR=0.53, 0.28-0.88). ASA plus clopidogrel was associated with the highest risk of major bleeding (OR=3.65, 1.22-13.56). In simulated comparisons, the novel oral anticoagulants ranked better than VKA or antiplatelet therapies for prevention of stroke, ischaemic stroke or systemic embolism and mortality.

CONCLUSIONS

In this network meta-analysis, novel oral anticoagulants were the most promising treatments to reduce stroke, stroke or systemic embolism, and all-cause mortality in patients with AF.

Management of Anticoagulant Therapy for Patients with Prosthetic Heart Valves or Atrial Fibrillation

There is a wide array of recommendations for the management of anticoagulant therapy in patients with mechanical heart valves. Especially the optimal intensity of vitamin K antagonists (VKA) is a ongoing matter of debate. On the basis of several studies, recommendations for daily clinical practice can be made. In this review, we discussed the studies and the different guidelines. Guidelines for the prevention of thromboembolic complications in patients with atrial fibrillation are more stringent. VKA with a target INR between 2.0 and 3.0 is more effective in the prevention of stroke than aspirin, especially in the presence of riskfactors for thromboembolism (age above 65, previous thromboembolism, history of hypertension and diabetes, enlarged left atrial diameter and left ventricular dysfunction). In the absence of clinical or echocardiographical riskfactors for thromboembolism, patients may be safely treated with aspirin.

Atherosclerosis and thromboembolic risk in atrial fibrillation: focus on peripheral vascular disease

Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice. It results in a 5-fold increased risk for stroke and thromboembolism and is associated with a high morbidity and mortality. AF shares several risk factors and pathophysiological features with atherosclerosis. Hence AF is often complicated by a variety of other cardiovascular conditions. Indeed, peripheral vascular disease (PVD) is highly prevalent among AF patients and associates with increased mortality. Inclusion of PVD within stroke risk scoring systems such as the CHA2DS2-VASc score improves risk stratification of AF patients. Of note, PVD has not been previously well documented nor looked for in observational studies or clinical trials. The aim of this present review article is to provide an overview of the association between atherosclerosis (with particular focus on PVD) and AF as well as its complications.

Prevention of Stroke by Antithrombotic Therapy in Patients with Atrial Fibrillation

Atrial Fibrillation (AF) is the most common clinically significant sustained cardiac arrhythmia, a major risk factor for strokes whether it is symptomatic or silent. The older CHADS₂ score and the newer CHADS₂-VASc are well validated to determine stroke risk and guide initiation of antithrombotic therapy, but haemorrhagic risk has to be respected as well, and scores such as HAS-BLED should be widely used. Old fashioned warfarin became standard of care outperforming antiplatelets in every trial but novel classes of anticoagulants that overcome many of warfarin drawbacks have been introduced and are already guideline recommended regiments. Nevertheless their use poses new questions that have to been answered in the near future.

Cost-effectiveness of apixaban compared with warfarin for stroke prevention in atrial fibrillation

BACKGROUND

Apixaban was shown to be superior to adjusted-dose warfarin in preventing stroke or systemic embolism in patients with atrial fibrillation (AF) and at least one additional risk factor for stroke, and associated with reduced rates of hemorrhage. We sought to determine the cost-effectiveness of using apixaban for stroke prevention.

METHODS

Based on the results from the Apixaban Versus Warfarin in Patients with Atrial Fibrillation (ARISTOTLE) trial and other published studies, we constructed a Markov model to evaluate the cost-effectiveness of apixaban versus warfarin from the Medicare perspective. The base-case analysis assumed a cohort of 65-year-old patients with a CHADS(2) score of 2.1 and no contraindication to oral anticoagulation. We utilized a 2-week cycle length and a lifetime time horizon. Outcome measures included costs in 2012 US$, quality-adjusted life-years (QALYs), life years saved and incremental cost-effectiveness ratios.

RESULTS

Under base case conditions, quality adjusted life expectancy was 10.69 and 11.16 years for warfarin and apixaban, respectively. Total costs were $94,941 for warfarin and $86,007 for apixaban, demonstrating apixaban to be a dominant economic strategy. Upon one-way sensitivity analysis, these results were sensitive to variability in the drug cost of apixaban and various intracranial hemorrhage related variables. In Monte Carlo simulation, apixaban was a dominant strategy in 57% of 10,000 simulations and cost-effective in 98% at a willingness-to-pay threshold of $50,000 per QALY.

CONCLUSIONS

In patients with AF and at least one additional risk factor for stroke and a baseline risk of ICH risk of about 0.8%, treatment with apixaban may be a cost-effective alternative to warfarin.

Pharmacologic and nonpharmacologic thromboprophylactic strategies in atrial fibrillation

Stroke prevention in atrial fibrillation (SPAF) has traditionally been confined to aspirin and warfarin therapy. Based on CHADS2 scoring it was clearly delineated when aspirin and warfarin would be used in individual patients, but many patients had to forgo recommended therapy due to contraindications or adverse events. There has recently been a paradigm shift in SPAF, with new and promising options on the horizon. These emerging strategies include dual antiplatelet therapy, direct thrombin inhibition, factor Xa inhibition and mechanical prophylaxis therapy. With each of these aforementioned approaches there are moderate to large clinical trials that assess the comparative effectiveness of these approaches in direct comparative trials. From an Ovid MEDLINE search from 1950 to present, we systematically identified 15 randomized trials comparing two thromboprophylactic drugs, devices or procedures for SPAF. Specific mechanical, pharmacologic and pharmacokinetic advantages and disadvantages are also reviewed.

Antithrombotic therapy for stroke prevention in atrial fibrillation and mechanical heart valves

Cardioembolic strokes account for one-sixth of all strokes and are an important potentially preventable cause of morbidity and mortality. Vitamin K antagonists (e.g., warfarin) are effective for the prevention of cardioembolic stroke in patients with atrial fibrillation (AF) and in those with mechanical heart valves but because of their inherent limitations are underutilized and often suboptimally managed. Antiplatelet therapies have been the only alternatives to warfarin for stroke prevention in AF but although they are safer and more convenient they are much less efficacious. The advent of new oral anticoagulant drugs offers the potential to reduce the burden of cardioembolic stroke by providing access to effective, safe, and more convenient therapies. New oral anticoagulants have begun to replace warfarin for stroke prevention in some patients with AF, based on the favorable results of recently completed phase III randomized controlled trials, and provide for the first time an alternative to antiplatelet therapy for patients deemed unsuitable for warfarin. The promise of the new oral anticoagulants in patients with mechanical heart valves is currently being tested in a phase II trial. If efficacy and safety are demonstrated, the new oral anticoagulants will provide an alternative to warfarin for patients with mechanical heart valves and may also lead to increased use of mechanical valves for patients who would not have received them in the past because of the requirement for long term warfarin therapy.

Antithrombotic therapy for atrial fibrillation: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

The risk of stroke varies considerably across different groups of patients with atrial fibrillation (AF). Antithrombotic prophylaxis for stroke is associated with an increased risk of bleeding. We provide recommendations for antithrombotic treatment based on net clinical benefit for patients with AF at varying levels of stroke risk and in a number of common clinical scenarios.

METHODS

We used the methods described in the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines article of this supplement.

RESULTS

For patients with nonrheumatic AF, including those with paroxysmal AF, who are (1) at low risk of stroke (eg, CHADS(2) [congestive heart failure, hypertension, age ≥ 75 years, diabetes mellitus, prior stroke or transient ischemic attack] score of 0), we suggest no therapy rather than antithrombotic therapy, and for patients choosing antithrombotic therapy, we suggest aspirin rather than oral anticoagulation or combination therapy with aspirin and clopidogrel; (2) at intermediate risk of stroke (eg, CHADS(2) score of 1), we recommend oral anticoagulation rather than no therapy, and we suggest oral anticoagulation rather than aspirin or combination therapy with aspirin and clopidogrel; and (3) at high risk of stroke (eg, CHADS(2) score of ≥ 2), we recommend oral anticoagulation rather than no therapy, aspirin, or combination therapy with aspirin and clopidogrel. Where we recommend or suggest in favor of oral anticoagulation, we suggest dabigatran 150 mg bid rather than adjusted-dose vitamin K antagonist therapy.

CONCLUSIONS

Oral anticoagulation is the optimal choice of antithrombotic therapy for patients with AF at high risk of stroke (CHADS(2) score of ≥ 2). At lower levels of stroke risk, antithrombotic treatment decisions will require a more individualized approach.

INR targets and site-level anticoagulation control: results from the Veterans AffaiRs Study to Improve Anticoagulation (VARIA)

BACKGROUND

Not all clinicians target the same International Normalized Ratio (INR) for patients with a guideline-recommended target range of 2-3. A patient's mean INR value suggests the INR that was actually targeted. We hypothesized that sites would vary by mean INR, and that sites of care with mean values nearest to 2.5 would achieve better anticoagulation control, as measured by per cent time in therapeutic range (TTR).

OBJECTIVES

To examine variations among sites in mean INR and the relationship with anticoagulation control in an integrated system of care.

PATIENTS/METHODS

We studied 103,897 patients receiving oral anticoagulation with an expected INR target between 2 and 3 at 100 Veterans Health Administration (VA) sites from 1 October 2006 to 30 September 2008. Key site-level variables were: proportion near 2.5 (that is, percentage of patients with mean INR between 2.3 and 2.7) and mean risk-adjusted TTR.

RESULTS

Site mean INR ranged from 2.22 to 2.89; proportion near 2.5, from 30 to 64%. Sites' proportions of patients near 2.5, below 2.3 and above 2.7 were consistent from year to year. A 10 percentage point increase in the proportion near 2.5 predicted a 3.8 percentage point increase in risk-adjusted TTR (P < 0.001).

CONCLUSIONS

Proportion of patients with mean INR near 2.5 is a site-level 'signature' of care and an implicit measure of targeted INR. This proportion varies by site and is strongly associated with site-level TTR. Our study suggests that sites wishing to improve TTR, and thereby improve patient outcomes, should avoid the explicit or implicit pursuit of non-standard INR targets.

Antithrombotic and thrombolytic therapy for ischemic stroke: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

OBJECTIVES

This article provides recommendations on the use of antithrombotic therapy in patients with stroke or transient ischemic attack (TIA).

METHODS

We generated treatment recommendations (Grade 1) and suggestions (Grade 2) based on high (A), moderate (B), and low (C) quality evidence.

RESULTS

In patients with acute ischemic stroke, we recommend IV recombinant tissue plasminogen activator (r-tPA) if treatment can be initiated within 3 h (Grade 1A) or 4.5 h (Grade 2C) of symptom onset; we suggest intraarterial r-tPA in patients ineligible for IV tPA if treatment can be initiated within 6 h (Grade 2C); we suggest against the use of mechanical thrombectomy (Grade 2C) although carefully selected patients may choose this intervention; and we recommend early aspirin therapy at a dose of 160 to 325 mg (Grade 1A). In patients with acute stroke and restricted mobility, we suggest the use of prophylactic-dose heparin or intermittent pneumatic compression devices (Grade 2B) and suggest against the use of elastic compression stockings (Grade 2B). In patients with a history of noncardioembolic ischemic stroke or TIA, we recommend long-term treatment with aspirin (75-100 mg once daily), clopidogrel (75 mg once daily), aspirin/extended release dipyridamole (25 mg/200 mg bid), or cilostazol (100 mg bid) over no antiplatelet therapy (Grade 1A), oral anticoagulants (Grade 1B), the combination of clopidogrel plus aspirin (Grade 1B), or triflusal (Grade 2B). Of the recommended antiplatelet regimens, we suggest clopidogrel or aspirin/extended-release dipyridamole over aspirin (Grade 2B) or cilostazol (Grade 2C). In patients with a history of stroke or TIA and atrial fibrillation we recommend oral anticoagulation over no antithrombotic therapy, aspirin, and combination therapy with aspirin and clopidogrel (Grade 1B).

CONCLUSIONS

These recommendations can help clinicians make evidence-based treatment decisions with their patients who have had strokes.

Effect of pharmacological therapies for stroke prevention on major gastrointestinal bleeding in patients with atrial fibrillation

Various antiplatelet and anticoagulation options are available for stroke prevention in patients with atrial fibrillation (AF). Currently, it is unclear whether these agents differ in their propensity to cause major gastrointestinal bleeding (MGIB). To our knowledge, no systematic evaluation of MGIB rates from randomised controlled trials (RCTs) of pharmacological stroke prevention in patients with AF has been conducted. Two independent investigators conducted systematic literature searches in MEDLINE and CENTRAL from the earliest possible date through November 2010. To be included, RCTs had to evaluate an adult population with AF or flutter and report data on the incidence of MGIB. Peto's odds ratios (ORs) with associated 95% confidence intervals (CIs) were calculated for all possible pair-wise comparisons of pharmacological stroke prevention alternatives. A total of 16 unique trials (n = 42,983) met inclusion criteria. The reported incidence of MGIB in placebo or control arms of identified trials was as high as 1.5%. Upon pair-wise meta-analysis of different pharmacological strategies, adjusted-dose vitamin K antagonists (VKAs) were found to be associated with a higher odds of MGIB compared with placebo/control (OR 3.21, 95% CI 1.32-7.82) and aspirin (or triflusal or indobufen) (OR 1.92, 95% CI 1.08-3.41). The addition of aspirin (or triflusal) to an adjusted-dose VKA resulted in greater odds of MGIB compared with aspirin alone (OR 4.72, 95% CI 1.35-16.49) and adjusted-dose VKA alone (OR 2.66, 95% CI 1.05-6.74). While aspirin increased the odds of MBIG by 3.23-fold compared with placebo/control, this finding did not reach statistical significance. The combination of aspirin and clopidogrel increased patients' odds of MGIB compared with aspirin alone (OR 1.93, 95% CI 1.46-2.56). Dabigatran was associated with a 30% increased odds of MGIB compared with adjusted-dose VKA (OR 1.30, 95% CI 1.06-1.59); however, ximelagatran was not. Low-intensity VKA therapy, alone or in combination with aspirin, was not associated with increased odds of MGIB compared with any (active-) comparator. The MGIB is a concern for patients with AF receiving pharmacological stroke prevention. Current RCT data suggest that dabigatran and adjusted-dose VKA therapy are associated with the highest odds of MGIB. Aspirin was not found to increase patients' odds of MGIB; however, this finding may be the result of type 2 error. Dual therapy resulting from the addition of an antiplatelet agent was typically associated with further increased odds of MGIB compared with monotherapy.

New approaches to stroke prevention in atrial fibrillation

OPINION STATEMENT

It is estimated that atrial fibrillation (AF) is responsible for almost 15% of all strokes. Several randomized clinical trials have demonstrated the superiority of adjusted-dose warfarin over aspirin for stroke prevention in AF patients, particularly in high-risk individuals. Current national guidelines from the American Heart Association/American Stroke Association recommend the use of adjusted-dose warfarin with an international normalized ratio goal of 2.0 to 3.0 for patients with ischemic stroke or transient ischemic attack with persistent or paroxysmal AF, and aspirin for those who cannot take oral anticoagulants. However, the use of warfarin may be challenging in some patients, and there is a need for alternative treatments. We describe alternative treatments for AF and provide an overview on emerging therapies.

Prevention of cardioembolic stroke

Cardiac causes of ischemic stroke lead to severe neurological deficits from large intracranial artery occlusion compared to small vessel ischemic stroke. The most common cause of cardioembolic stroke is atrial fibrillation (AF), which has an increasing incidence with age. AF stroke trials demonstrate that anti-coagulation is superior to anti-platelet therapy in terms of ischemic stroke prevention. Recently, warfarin was compared with dabigatran, an oral, direct thrombin inhibitor, and was found to be at least equally effective in reducing ischemic stroke with less intracranial bleeding risk. Future research is investigating other direct thrombin inhibitors as potential alternatives to warfarin, which has a narrow therapeutic index, requires frequent blood monitoring, has multiple drug interactions, and a higher rate of intracranial bleeding. Other causes of cardioembolic stroke include myocardial infarction, left ventricular thrombus, reduced ejection fraction, valvular abnormalities, and endocarditis. Patent foramen ovale is a common finding on echocardiograms in patients with and without stroke (up to 20% of the population), and it is a controversial source of cryptogenic stroke. The best way to prevent cardioembolic stroke remains early detection and treatment of AF, and treating the underlying stroke mechanism. Cardiac magnetic resonance imaging is an emerging technology and reveals some sources of cardiac embolism missed by echocardiography, and might provide an additional diagnostic tool in investigating cardioembolic stroke.

The business case for quality improvement: oral anticoagulation for atrial fibrillation

BACKGROUND

The potential to save money within a short time frame provides a more compelling "business case" for quality improvement than merely demonstrating cost-effectiveness. Our objective was to demonstrate the potential for cost savings from improved control in patients anticoagulated for atrial fibrillation.

METHODS AND RESULTS

Our population consisted of 67 077 Veterans Health Administration patients anticoagulated for atrial fibrillation between October 1, 2006, and September 30, 2008. We simulated the number of adverse events and their associated costs and utilities, both before and after various degrees of improvement in percent time in therapeutic range (TTR). The simulation had a 2-year time horizon, and costs were calculated from the perspective of the payer. In the base-case analysis, improving TTR by 5% prevented 1114 adverse events, including 662 deaths; it gained 863 quality-adjusted life-years and saved $15.9 million compared with the status quo, not accounting for the cost of the quality improvement program. Improving TTR by 10% prevented 2087 events, gained 1606 quality-adjusted life-years, and saved $29.7 million. In sensitivity analyses, costs were most sensitive to the estimated risk of stroke and the expected stroke reduction from improved TTR. Utilities were most sensitive to the estimated risk of death and the expected mortality benefit from improved TTR.

CONCLUSIONS

A quality improvement program to improve anticoagulation control probably would be cost-saving for the payer, even if it were only modestly effective in improving control and even without considering the value of improved health. This study demonstrates how to make a business case for a quality improvement initiative.

Cost-Effectiveness of Dabigatran for Stroke Prophylaxis in Atrial Fibrillation

Background—

Recent studies have investigated alternatives to warfarin for stroke prophylaxis in patients with atrial fibrillation (AF), but whether these alternatives are cost-effective is unknown.

Methods and Results—

On the basis of the results from Randomized Evaluation of Long Term Anticoagulation Therapy (RE-LY) and other trials, we developed a decision-analysis model to compare the cost and quality-adjusted survival of various antithrombotic therapies. We ran our Markov model in a hypothetical cohort of 70-year-old patients with AF using a cost-effectiveness threshold of $50 000/quality-adjusted life-year. We estimated the cost of dabigatran as US $9 a day. For a patient with an average risk of major hemorrhage (≈3%/y), the most cost-effective therapy depended on stroke risk. For patients with the lowest stroke rate (CHADS 2 stroke score of 0), only aspirin was cost-effective. For patients with a moderate stroke rate (CHADS 2 score of 1 or 2), warfarin was cost-effective unless the risk of hemorrhage was high or quality of international normalized ratio control was poor (time in the therapeutic range <57.1%). For patients with a high stroke risk (CHADS 2 stroke score ≥3), dabigatran 150 mg (twice daily) was cost-effective unless international normalized ratio control was excellent (time in the therapeutic range >72.6%). Neither dabigatran 110 mg nor dual therapy (aspirin and clopidogrel) was cost-effective.

Conclusions—

Dabigatran 150 mg (twice daily) was cost-effective in AF populations at high risk of hemorrhage or high risk of stroke unless international normalized ratio control with warfarin was excellent. Warfarin was cost-effective in moderate-risk AF populations unless international normalized ratio control was poor.

Canadian Cardiovascular Society atrial fibrillation guidelines 2010: prevention of stroke and systemic thromboembolism in atrial fibrillation and flutter

The stroke rate in atrial fibrillation is 4.5% per year, with death or permanent disability in over half. The risk of stroke varies from under 1% to over 20% per year, related to the risk factors of congestive heart failure, hypertension, age, diabetes, and prior stroke or transient ischemic attack (TIA). Major bleeding with vitamin K antagonists varies from about 1% to over 12% per year and is related to a number of risk factors. The CHADS(2) index and the HAS-BLED score are useful schemata for the prediction of stroke and bleeding risks. Vitamin K antagonists reduce the risk of stroke by 64%, aspirin reduces it by 19%, and vitamin K antagonists reduce the risk of stroke by 39% when directly compared with aspirin. Dabigatran is superior to warfarin for stroke prevention and causes no increase in major bleeding. We recommend that all patients with atrial fibrillation or atrial flutter, whether paroxysmal, persistent, or permanent, should be stratified for the risk of stroke and for the risk of bleeding and that most should receive antithrombotic therapy. We make detailed recommendations as to the preferred agents in various types of patients and for the management of antithrombotic therapies in the common clinical settings of cardioversion, concomitant coronary artery disease, surgical or diagnostic procedures with a risk of major bleeding, and the occurrence of stroke or major bleeding. Alternatives to antithrombotic therapies are briefly discussed.