Predictors of warfarin use in atrial fibrillation in the United States: a systematic review and meta-analysis

Characterization of patients with atrial fibrillation not treated with oral anticoagulants

OBJECTIVE

An underuse of oral anticoagulants (OAC) in patients with atrial fibrillation (AF) has been suggested, as only 50% of all patients with AF receive OAC treatment. Whether this is due to contraindications, lack of an indication to treat, or an expression of underuse is sparsely investigated. This study therefore aimed to characterize individuals without OAC treatment in a real-life population of patients with AF.

DESIGN

Retrospective cross-sectional study. The medical records were scrutinized in order to identify the type of AF, risk factors for embolism and bleeding, and other factors of importance for OAC treatment.

SETTING

The municipalities of Skellefteå and Norsjö, northern Sweden.

SUBJECTS

A total of 2274 living residents with at least one verified episode of AF on or before December 31, 2010.

MAIN OUTCOME MEASURES

Prevalence of treatment with OAC and documented reasons to withhold OAC treatment.

RESULTS

Among all 2274 patients with AF, 1187 (52%) were not treated with OAC. Of the untreated patients, 19% had no indication or had declined or had experienced adverse effects other than bleeding on warfarin treatment. The most common reason to withhold OAC was presence of risk factors for bleeding, found in 38% of all untreated patients. Furthermore, a documented reason could be identified to withhold OAC in 75%.

CONCLUSIONS

Among patients with AF without OAC treatment a reason could be identified to withhold OAC in 75%. The underuse of OAC is estimated to be 25%.

Impact of atrial fibrillation on healthcare utilization in the community: the Atherosclerosis Risk in Communities study

Background

Atrial fibrillation (AF) is associated with increased risk of hospitalization. Little is known about the impact of AF on utilization of noninpatient health care or about sex or race differences in AF‐related utilization. We examined rates of inpatient and outpatient utilization by AF status in the Atherosclerosis Risk in Communities study.

Methods and Results

Participants with incident AF enrolled in fee‐for‐service Medicare for at least 12 continuous months between 1991 and 2009 (n=932) were matched on age, sex, race and field center with up to 3 participants without AF (n=2729). Healthcare utilization was ascertained from Medicare claims and classified by primary International Classification of Diseases, ninth revision code. The average annual numbers of days hospitalized were 13.2 (95% CI 11.6 to 15.0) and 2.8 (95% CI 2.5 to 3.1) for those with and without AF, respectively. The corresponding numbers of annual outpatient claims were 53.3 (95% CI 50.5 to 56.3) and 22.9 (95% CI 22.1 to 23.8) for those with and without AF, respectively. Most utilization among AF patients was attributable to non‐AF conditions. The adjusted rate ratio for annual days hospitalized for other cardiovascular disease–related reasons was 4.58 (95% CI: 3.41 to 6.16) for those with AF versus those without AF. The association between AF and healthcare utilization was similar among men and women and among white and black participants.

Conclusions

Participants with AF had considerably greater healthcare utilization, and the difference in utilization for other cardiovascular disease–related reasons was substantial. In addition to rate or rhythm treatment, AF management should focus on the accompanying cardiovascular comorbidities.

Magnetic resonance imaging of the left atrial appendage post pulmonary vein isolation: Implications for percutaneous left atrial appendage occlusion

BACKGROUND

There is increasing interest in performing left atrial appendage (LAA) occlusion at the time of atrial fibrillation (AF) ablation procedures. However, to date there has been no description of the acute changes to the LAA immediately following pulmonary vein (PV) isolation and additional left atrium (LA) substrate modification. This study assessed changes in the size and tissue characteristics of the LAA ostium in patients undergoing PV isolation.

METHODS

This series included 8 patients who underwent cardiovascular magnetic resonance evaluation of the LA with delayed enhancement magnetic resonance imaging and contrast enhanced 3-D magnetic resonance angiography pre-, within 48 h of, and 3 months post ablation. Two independent cardiac radiologists evaluated the ostial LAA diameters and area at each time point in addition to the presence of gadolinium enhancement.

RESULTS

Compared to pre-ablation values, the respective median differences in oblique diameters and LAA area were +1.8 mm, +1.7 mm, and +0.6 cm(2) immediately post ablation (all NS) and -2.7 mm, -2.3 mm, and -0.5 cm(2) at 3 months (all NS). No delayed enhancement was detected in the LAA post ablation.

CONCLUSION

No significant change to LAA diameter, area, or tissue characteristics was noted after PV isolation. While these findings suggest the safety and feasibility of concomitant PV isolation and LAA device occlusion, the variability in the degree and direction of change of the LAA measurements highlights the need for further study.

Impact of stated barriers on proposed warfarin prescription for atrial fibrillation: a survey of Canadian physicians

BACKGROUND

Atrial fibrillation (AF) is a common cardiac arrhythmia, and leading cause of ischemic stroke. Despite proven effectiveness, warfarin remains an under-used treatment in atrial fibrillation patients. We sought to study, across three physician specialties, a range of factors that have been argued to have a disproportionate effect on treatment decisions.

METHODS

Cross-sectional survey of Canadian Family Doctors (FD: n = 500), Geriatricians (G: n = 149), and Internal Medicine specialists (IMS: n = 500). Of these, 1032 physicians were contactable, and 335 completed and usable responses were received. Survey questions and clinical vignettes asked about the frequency with which they see patients with atrial fibrillation, treatment practices, and barriers to the prescription of anticoagulants.

RESULTS

Stated prescribing practices did not significantly differ between physician groups. Falls risk, bleeding risk and poor patient adherence were all highly cited barriers to prescribing warfarin. Fewer geriatricians indicated that history of patient falls would be a reason for not treating with warfarin (G: 47%; FD: 71%; IMS: 72%), and significantly fewer changed reported practice in the presence of falls risk (χ (2) (6) = 45.446, p < 0.01). Experience of a patient having a stroke whilst not on warfarin had a significant impact on vignette decisions; physicians who had had patients who experienced a stroke were more likely to prescribe warfarin (χ (2) (3) =10.7, p = 0.013).

CONCLUSIONS

Barriers to treatment of atrial fibrillation with warfarin affect physician specialties to different extents. Prior experience of a patient suffering a stroke when not prescribed warfarin is positively associated with intention to prescribe warfarin, even in the presence of falls risk.

Patient self-management of oral anticoagulation with vitamin K antagonists in everyday practice: efficacy and safety in a nationwide long-term prospective cohort study

Patient self-management (PSM) of oral anticoagulation is under discussion, because evidence from real-life settings is missing. Using data from a nationwide, prospective cohort study in Switzerland, we assessed overall long-term efficacy and safety of PSM and examined subgroups. Data of 1140 patients (5818.9 patient-years) were analysed and no patient were lost to follow-up. Median follow-up was 4.3 years (range 0.2-12.8 years). Median age at the time of training was 54.2 years (range 18.2-85.2) and 34.6% were women. All-cause mortality was 1.4 per 100 patient-years (95% CI 1.1-1.7) with a higher rate in patients with atrial fibrillation (2.5; 1.6-3.7; p<0.001), patients>50 years of age (2.0; 1.6-2.6; p<0.001), and men (1.6; 1.2-2.1; p = 0.036). The rate of thromboembolic events was 0.4 (0.2-0.6) and independent from indications, sex and age. Major bleeding were observed in 1.1 (0.9-1.5) per 100 patient-years. Efficacy was comparable to standard care and new oral anticoagulants in a network meta-analysis. PSM of properly trained patients is effective and safe in a long-term real-life setting and robust across clinical subgroups. Adoption in various clinical settings, including those with limited access to medical care or rural areas is warranted.

A non-experimental study of oral anticoagulation therapy initiation before and after national patient safety goals

OBJECTIVES

The Joint Commission revised its National Patient Safety Goals (NPSGs) to include oral anticoagulation therapy (OAT) in 2008. We sought to examine the effect of including OAT in The Joint Commission's NPSGs on historically low rates of OAT initiation for individuals with incident atrial fibrillation (AF).

SETTING

Southeastern state in the USA.

PARTICIPANTS

North Carolina State Health Plan claims data from 944 500 individuals enrolled between 1 January 2006 and 31 December 2010, supplemented with data from the Area Resource File and Online Survey, Certification and Reporting data network. We evaluated OAT initiation before and after the 2008 NPSGs revisions in a retrospective cohort new user design with an AF intervention group and two control groups: a positive control-patients estimated to be at very high risk of thromboembolism (mechanical heart valve and pulmonary embolism); and a negative control-patients with very low perceived risk of thromboembolism (paroxysmal AF). We developed multivariable models using a difference-in-difference parameterisation. Effects were estimated with generalised estimating equations.

PRIMARY OUTCOME MEASURE

OAT initiation, a binary outcome defined as having a prescription drug claim for warfarin within 30 days of the index claim.

RESULTS

OAT initiation was low (26.8%) for eligible individuals with incident AF in 2006-2008 but increased after NPSGs implementation (31.7%, p=0.022). OAT initiation was high but decreased in the positive control group (67.5% vs 62.0%, p=0.003). Multivariate analysis resulted in a relative 11% (95% CI (4% to 18%), p<0.01) increase in OAT initiation for incident AF patients.

CONCLUSIONS

We document a substantial increase in guideline concordant OAT initiation in incident AF after the establishment of NPSGs, suggesting that regulatory healthcare agency initiatives can influence clinical practice.

Genetic risk factors for major bleeding in patients treated with warfarin in a community setting

The influence of warfarin pharmacogenomics on major bleeding risk has been little studied in long-term users and non-specialist care settings. We conducted a case-control study to evaluate associations between CYP2C9*2/*3, VKORC1(1173), and CYP4F2*3 variants and major bleeding among patients treated with warfarin in a community setting. We calculated major bleeding odds ratios, adjusting for race, duration of warfarin use, age, gender, and body mass index. In 265 cases and 305 controls with 3.4 and 3.7 mean years of warfarin use, respectively, CYP4F2*3 was associated with decreased major bleeding risk (odds ratio: 0.62; 95% confidence interval: 0.43-0.91). CYP2C9*2/*3 and VKORC1(1173) had null associations overall, but there was a nonsignificant increase in major bleeding risk in patients with duration <6 months (odds ratio: 1.30; 95% confidence interval: 0.60-2.83; odds ratio: 1.23; 95% confidence interval: 0.57-2.64, respectively). In summary, in the largest study of warfarin pharmacogenomics and major bleeding to date, we found a 38% lower risk in patients with CYP4F2*3, potentially reflecting interaction with warfarin and dietary vitamin K intake and warranting additional evaluation.

Identifying the risks of anticoagulation in patients with substance abuse

BACKGROUND

Warfarin is effective in preventing thromboembolic events, but concerns exist regarding its use in patients with substance abuse.

OBJECTIVE

Identify which patients with substance abuse who receive warfarin are at risk for poor outcomes.

DESIGN

Retrospective cohort study. Diagnostic codes, lab values, and other factors were examined to identify risk of adverse outcomes.

PATIENTS

Veterans AffaiRs Study to Improve Anticoagulation (VARIA) database of 103,897 patients receiving warfarin across 100 sites.

MAIN MEASURES

Outcomes included percent time in therapeutic range (TTR), a measure of anticoagulation control, and major hemorrhagic events by ICD-9 codes.

RESULTS

Nonusers had a higher mean TTR (62 %) than those abusing alcohol (53 %), drugs (50 %), or both (44 %, p < 0.001). Among alcohol abusers, an increasing ratio of the serum hepatic transaminases aspartate aminotransferase/alanine aminotransferase (AST:ALT) correlated with inferior anticoagulation control; normal AST:ALT ≤ 1.5 predicted relatively modest decline in TTR (54 %, p < 0.001), while elevated ratios (AST:ALT 1.50-2.0 and > 2.0) predicted progressively poorer anticoagulation control (49 % and 44 %, p < 0.001 compared to nonusers). Age-adjusted hazard ratio for major hemorrhage was 1.93 in drug and 1.37 in alcohol abuse (p < 0.001 compared to nonusers), and remained significant after also controlling for anticoagulation control and other bleeding risk factors (1.69 p < 0.001 and 1.22 p = 0.003). Among alcohol abusers, elevated AST:ALT >2.0 corresponded to more than three times the hemorrhages (HR 3.02, p < 0.001 compared to nonusers), while a normal ratio AST:ALT ≤ 1.5 predicted a rate similar to nonusers (HR 1.19, p < 0.05).

CONCLUSIONS

Anticoagulation control is particularly poor in patients with substance abuse. Major hemorrhages are more common in both alcohol and drug users. Among alcohol abusers, the ratio of AST/ALT holds promise for identifying those at highest risk for adverse events.

Anticoagulant therapy with the oral direct factor Xa inhibitors rivaroxaban, apixaban and edoxaban and the thrombin inhibitor dabigatran etexilate in patients with hepatic impairment

The direct factor Xa (FXa) inhibitors rivaroxaban, apixaban and edoxaban, and the thrombin inhibitor dabigatran etexilate (dabigatran) have gained approval for use in several indications, most notably for the prevention and treatment of venous thromboembolism (VTE) and for the prevention of stroke in patients with atrial fibrillation. Hepatic impairment can affect the disposition of these anticoagulants considerably not only because of the hepatic metabolism of the direct FXa inhibitors but also because moderate to severely impaired hepatic function will affect coagulation. This review describes the key pharmacological properties of novel oral anticoagulants with special attention to patients with impaired hepatic function. In subjects with moderately impaired liver function (i.e. Child-Pugh classification B), the area under the plasma concentration-time curve (AUC) of rivaroxaban (10 mg single dose) is increased by 2.27-fold, which is paralleled by an increase in FXa inhibition. The AUC of apixaban (5 mg single dose) is increased by 1.09-fold, whereas the AUC of edoxaban (15 mg single dose) is decreased by 4.8 % and the AUC of dabigatran (150 mg single dose) is decreased by 5.6 %. Specific labelling restrictions for rivaroxaban, apixaban and dabigatran regarding impaired hepatic function are based on both the Child-Pugh classification and liver-related exclusion criteria applied in pivotal clinical trials. Rivaroxaban is contraindicated in patients with hepatic disease associated with coagulopathy and clinically relevant bleeding risk, including cirrhotic patients classified as Child-Pugh B and C. Apixaban can be used with caution in patients with mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment or in patients with alanine aminotransferase and aspartate aminotransferase levels >2× upper limit of normal (ULN). Apixaban is not recommended in patients with severe hepatic impairment and is contraindicated in those with hepatic disease associated with coagulopathy and clinically relevant bleeding risk. Dabigatran is not recommended in patients with elevated liver enzymes (>2× ULN). Dabigatran is contraindicated in patients with hepatic impairment or liver disease expected to have any impact on survival. Currently, edoxaban is not available in the US or European markets. However, the Japanese label did not restrict use in hepatic dysfunction but advises care in patients with severe hepatic impairment.

Predictors of Anticoagulant Treatment in Patients With Nonvalvular Atrial Fibrillation

The aim of the study was to assess the factors associated with the anticoagulation treatment in patients with atrial fibrillation (AF). A total of 2242 consecutive patients who had been admitted with AF on their electrocardiogram were included in the study. After excluding valvular AF, 1745 patients with nonvalvular AF were analyzed. Mean CHA2DS2-VASc score [cardiac failure, hypertension, age ≥ 75 (doubled), diabetes, stroke (doubled), vascular disease, age 65 -74 and sex category (female)], frequency of persistent/permanent AF, hypertension, diabetes mellitus (DM), stroke history, body mass index, and left atrial diameter were significantly higher in patients receiving anticoagulant therapy. Stroke history, persistent/permanent AF, hypertension, DM, age, heart failure, and left atrial diameter were independent predictors of warfarin prescription. Labile international normalized ratio was the only independent negative predictor of effective treatment with warfarin. In this study, we demonstrated that stroke history, persistent/permanent AF, hypertension, DM, and left atrial diameter were positive predictors, whereas advanced age and heart failure were negative predictors of oral anticoagulant use in patients with nonvalvular AF.

Economic evaluation of percutaneous left atrial appendage occlusion, dabigatran, and warfarin for stroke prevention in patients with nonvalvular atrial fibrillation

BACKGROUND

Percutaneous left atrial appendage (LAA) occlusion and novel pharmacological therapies are now available to manage stroke risk in patients with nonvalvular atrial fibrillation; however, the cost-effectiveness of LAA occlusion compared with dabigatran and warfarin in patients with nonvalvular atrial fibrillation is unknown.

METHODS AND RESULTS

Cost-utility analysis using a patient-level Markov microsimulation decision analytic model with a lifetime horizon was undertaken to determine the lifetime costs, quality-adjusted life years, and incremental cost-effectiveness ratio of LAA occlusion in relation to dabigatran and warfarin in patients with nonvalvular atrial fibrillation at risk for stroke without contraindications to oral anticoagulation. The analysis was performed from the perspective of the Ontario Ministry of Health and Long Term Care, the third-party payer for insured health services in Ontario, Canada. Effectiveness and utility data were obtained from the published literature. Cost data were obtained from the Ontario Drug Benefits Formulary and the Ontario Case Costing Initiative. Warfarin therapy had the lowest discounted quality-adjusted life years at 4.55, followed by dabigatran at 4.64 and LAA occlusion at 4.68. The average discounted lifetime cost was $21 429 for a patient taking warfarin, $25 760 for a patient taking dabigatran, and $27 003 for LAA occlusion. Compared with warfarin, the incremental cost-effectiveness ratio for LAA occlusion was $41 565. Dabigatran was extendedly dominated.

CONCLUSIONS

Percutaneous LAA occlusion represents a novel therapy for stroke reduction that is cost-effective compared with warfarin for patients at risk who have nonvalvular atrial fibrillation.

Patterns of warfarin use in subgroups of patients with atrial fibrillation: a cross-sectional analysis of 430 general practices in the United Kingdom

BACKGROUND

Despite the proven efficacy of warfarin, its use in patients with Atrial Fibrillation (AF) is reportedly low. We investigated the underuse and overuse of warfarin in the management of AF in general practices in the United Kingdom (UK) against the National Institute of Clinical Excellence (NICE, UK) guidelines whilst seeking to identify subgroups of AF patients to inform efforts to optimise warfarin use.

METHODOLOGY

A retrospective database analysis to determine warfarin prescribing using tree models based on 50,361 patients with AF (classified as low, moderate and high risk of stroke using CHADS2) from 430 general practices in the UK.

RESULTS

Over one-third (37.0%, 4573/12,351) of low risk AF patients were on warfarin, compared with 47.1% (8349/17,709) moderate risk AF patients and 54.9% (11,142/20,301) high risk AF patients. Clinical subgroups (n = 15 low risk subgroups, n = 15 medium risk subgroups, n = 22 high risk subgroups) were identified. Several factors not supported by current guidelines (age, BMI, dementia, gender) were associated with the use of warfarin. Gender and BMI were associated with warfarin use in low and medium risk AF patients but not in high risk AF patients.

CONCLUSION

Whilst NICE guidelines suggest that all high risk AF patients should be on warfarin, half of those at moderate risk should be on warfarin and none of those at low risk should be on warfarin, we found evidence of over and under use of warfarin. Interventions to optimise warfarin therapy tailored to and targeting specific subgroups of AF patients identified by the tree models are required.

Comparative effectiveness of dabigatran, rivaroxaban, apixaban, and warfarin in the management of patients with nonvalvular atrial fibrillation

Alternative anticoagulants to warfarin (dabigatran, rivaroxaban, and apixaban) are becoming available for the prevention of thromboembolic stroke in atrial fibrillation (AF), but there is a lack of information on their comparative effectiveness. Using a discrete event simulation method adopting a lifetime horizon of analysis, we made an indirect comparison of the RE-LY, ROCKET-AF, and ARISTOTLE trial results for AF patients in the US population. Over a lifetime, apixaban, dabigatran, and rivaroxaban accrued 0.130 (95% central range (CR) -0.030 to 0.264), 0.106 (95% CR -0.048 to 0.248), and 0.095 (95% CR -0.052 to 0.242) more quality-adjusted life-years (QALYs), respectively, than warfarin, with apixaban having a 55% probability of accruing the highest total QALYs. In the absence of a definitive trial, and acknowledging the limitations of an indirect comparison, the available evidence suggests apixaban to be the most effective anticoagulant.

Apixaban: a new factor Xa inhibitor for stroke prevention in patients with nonvalvular atrial fibrillation

Atrial fibrillation (AF) is an independent risk factor for ischemic stroke occurrence, severity, recurrence, and mortality. Anticoagulation therapy for the prevention of thromboembolism is critical in patients with AF who are at risk of stroke. Warfarin has been an efficacious anticoagulant for this purpose, but its use has been limited by frequent laboratory monitoring, drug interactions, unpredictable individual response, delayed onset of action, and bleeding. Apixaban is the second oral direct selective factor Xa inhibitor approved for the prevention of stroke/systemic embolism in patients with nonvalvular AF. It was significantly better than aspirin in reducing stroke (ischemic or hemorrhagic) or systemic embolism without increasing the risk of major bleeding in patients with AF who were at increased risk of stroke and for whom warfarin was unsuitable. In a randomized, double-blind trial that was originally designed to test for noninferiority, apixaban was superior to warfarin (target international normalized ratio 2-3) in preventing stroke or systemic embolism, caused less bleeding, and resulted in lower mortality in patients with AF. Apixaban has a half-life of about 12 hours, and the normal dosage is 5 mg orally twice daily. However, it may be reduced to 2.5 mg twice daily based on individual factors of the patient (age, renal function, and body weight) and the concomitant use of potent dual inhibitors of cytochrome P450 3A4 and P-glycoprotein. Similar to other novel oral anticoagulants (dabigatran and rivaroxaban), apixaban has no reversal agent for its anticoagulant effect. Overall, apixaban is a safe and efficacious alternative for stroke prophylaxis in high-risk patients who have AF and who are unable to achieve therapeutic goals with warfarin therapy.

Review of epidemiology and management of atrial fibrillation in developing countries

BACKGROUND

Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia. In developing countries, AF is a growing public health problem with the epidemiologic transition from communicable to non-communicable diseases. However, relatively little is known about AF in the developing world. The aim of this review is to examine in developing countries the prevalence, associated medical conditions and management of AF.

METHODS

A literature search was conducted via MEDLINE and EMBASE (1990-2012).

RESULTS

Seventy studies were included in the review. The prevalence of AF in the general population ranged from 0.03% to 1.25%, while the prevalence of AF in hospital-based studies varied from 0.7% to 55.7%. Prevalence of AF in Africa was lower than in other regions. The most common conditions associated with AF were hypertension (10.3%-71.9%) and valvular heart disease (5.6%-66.3%). The prevalence of stroke in patients with AF ranged from 6.7% to 27%. The utilization of anticoagulants was highly variable (2.7%-72.7%). Approximately half of the patients with AF using warfarin had therapeutic International Normalized Ratios (INR). There was a high prevalence of use of rate control therapies (55.3%-87.3%).

CONCLUSIONS

The limited studies available suggest that in the developing world there is a significant prevalence of AF, which is predominantly associated with hypertension and valvular heart disease, and carries a risk of stroke. Highly variable use of anticoagulants may be related to different health care and socioeconomic settings. More studies are needed to improve understanding of the epidemiology and management of AF in developing countries.

Atrial fibrillation and thromboprophylaxis in heart failure: the need for patient-centered approaches to address adherence

Atrial fibrillation is a common arrhythmia in heart failure and a risk factor for stroke. Risk assessment tools can assist clinicians with decision making in the allocation of thromboprophylaxis. This review provides an overview of current validated risk assessment tools for atrial fibrillation and emphasizes the importance of tailoring individual risk and the importance of weighing the benefits of treatment. Further, this review provides details of innovative and patient-centered methods for ensuring optimal adherence to prescribed therapy. Prior to initiating oral anticoagulant therapy, a comprehensive risk assessment should include evaluation of associated cardiogeriatric conditions, potential for adherence to prescribed therapy, frailty, and functional and cognitive ability.