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Original Research: Antithrombotic Therapy |

Time Trends of Aspirin and Warfarin Use on Stroke and Bleeding Events in Chinese Patients With New-Onset Atrial FibrillationAtrial Fibrillation in China FREE TO VIEW

Yutao Guo, MD, PhD; Hao Wang, MD; Yingchun Tian, MD; Yutang Wang, MD, PhD; Gregory Y. H. Lip, MD
Author and Funding Information

From the Department of Geriatric Cardiology (Drs Guo, H. Wang, and Y. Wang), Chinese PLA General Hospital, Beijing, China; Department of Gerontology (Drs Tian and Lip), Second People’s Hospital, Yunnan Province, China; University of Birmingham Centre for Cardiovascular Sciences (Dr Lip), City Hospital, Birmingham, England; and Aalborg Thrombosis Research Unit (Dr Lip), Department of Clinical Medicine, Faculty of Health, Aalborg University, Aalborg, Denmark.

CORRESPONDENCE TO: Gregory Y. H. Lip, MD, University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Dudley Rd, Birmingham, B18 7QH, England; e-mail: g.y.h.lip@bham.ac.uk


Drs Y. Wang and Lip are joint senior authors on this paper.

FUNDING/SUPPORT: The authors have reported to CHEST that no funding was received for this study.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2015;148(1):62-72. doi:10.1378/chest.14-2018
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BACKGROUND:  Much of the clinical epidemiology and treatment patterns for patients with atrial fibrillation (AF) are derived from Western populations. Limited data are available on antithrombotic therapy use over time and its impact on the stroke or bleeding events in newly diagnosed Chinese patients with AF. The present study investigates time trends in warfarin and aspirin use in China in relation to stroke and bleeding events in a Chinese population.

METHODS:  We used a medical insurance database involving > 10 million individuals for the years 2001 to 2012 in Yunnan, a southwestern province of China, and performed time-trend analysis on those with newly diagnosed AF. Cox proportional hazards time-varying exposures were used to determine the risk of stroke or bleeding events associated with antithrombotic therapy among patients with AF.

RESULTS:  Among the randomly sampled 471,446 participants, there were 1,237 patients with AF, including 921 newly diagnosed with AF, thus providing 4,859 person-years of experience (62% men; mean attained age, 70 years). The overall rate of antithrombotic therapy was 37.7% (347 of 921 patients), with 4.1% (38 of 921) on warfarin and 32.3% (298 of 921) on aspirin. Antithrombotic therapy was not related to stroke/bleeding risk scores (CHADS2 [congestive heart failure, hypertension, age ≥ 75 years, diabetes, stroke (doubled)] score, P = .522; CHA2DS2-VASc [congestive heart failure, hypertension, age ≥ 75 years (doubled), diabetes mellitus, stroke or transient ischemic attack (doubled), vascular disease, age 65 to 74 years, and female sex] score, P = .957; HAS-BLED [hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly (> 65 years), drugs/alcohol concomitantly] score, P = .095). The use of antithrombotic drugs (mainly aspirin) increased in both women and men over time, with the rate of aspirin increasing from 4.0% in 2007 to 46.1% in 2012 in the former, and from 7.7% in 2007 to 61.9% in 2012 in the latter (P for trend for both, < .005). In the overall cohort, the annual stroke rate was approximately 6% and the annual major bleeding rate was about 1%. Compared with nonantithrombotic therapy, the hazard ratio for ischemic stroke was 0.68 (95% CI, 0.39-1.18) for aspirin and 1.39 (0.54-3.59) for warfarin.

CONCLUSIONS:  Aspirin use increased among Chinese patients newly diagnosed with AF, with no relationship to the patient’s stroke or bleeding risk. Warfarin use was very low. Given the health-care burden of AF and its complications, our study has major implications for health-care systems in non-Western countries, given the global burden of this common arrhythmia.

Figures in this Article

The prevalence and incidence of atrial fibrillation (AF) are increasing globally, which is having a profound impact on patient disability and mortality.1 The most serious, common complication of AF is thromboembolism (TE), and AF-related stroke is associated with a 30-day mortality of 24%. Thus, thromboprophylaxis with oral anticoagulation is strongly recommended for patients with AF who have one or more stroke risk factors.

For nearly 50 years, vitamin K antagonists (eg, warfarin) have been used as oral anticoagulants for stroke prevention in AF. Overall prevalence of warfarin treatment was 55% in patients with AF who had a CHADS2 (congestive heart failure, hypertension, age ≥ 75 years, diabetes, stroke [doubled]) score > 1 in the United States,2 and 80% among European cardiology practices.2,3 Indeed, warfarin use has been increasing in Western countries. For example, in a Minnesota community-based study, warfarin use increased from 9% from 1980 to 1984 to 30% in the period from 1995 to 2000, as did aspirin use (from 18% to 52%); these were associated with a reduction in stroke by 3.4% per year.4 Some of the various limitations of warfarin have been overcome by the introduction of non-vitamin K antagonist oral anticoagulants (NOACs) (eg, dabigatran, rivaroxaban, apixaban), given their approvals in North America and Europe for stroke prevention in patients with AF.

However, in most Asian countries, suboptimal thromboprophylaxis in AF is still common.5 In a Japanese cohort with AF, the rates of warfarin and antiplatelet agent use were 48% and 31%, respectively, while the rate of stroke, transient ischemic attack (TIA), or systemic TE was as high as 22%.6 Our previous hospital-based study found that only 14% of patients in a Chinese cohort with AF were receiving warfarin and 60% were taking aspirin, while the rates of stroke or systemic TE and the bleeding events in a 2-year period were 8% and 5%, respectively.7

Although there are substantial data on antithrombotic management in Western populations,8 the information on AF epidemiology and antithrombotic management over time in Asian countries is limited. Limited data are available on antithrombotic therapy use over time and its impact on the stroke or bleeding events in Chinese patients newly diagnosed with AF.

To address this issue, first we studied time trends of antithrombotic therapy with relation to stroke and bleeding events in Chinese patients with new-onset AF during an 11-year period (2001 to 2012), using a large medical insurance database including > 10 million people. Second, the impact of antithrombotic therapy on stroke and bleeding risk was evaluated in this real-world Chinese population with AF. Third, a comparison was made with published data from Western countries.

Database Description

The medical insurance database in the Yunnan Province, China, from January 1, 2001, through December 30, 2012, was used. This database includes > 10 million individuals who enrolled in a large, governmental medical insurance plan. This medical insurance scheme covers urban residents in Yunnan Province, located in the far southwest of China, spanning approximately 394,000 km2 and with a population of 46.3 million (2011 population statistics), representing 3% of the total Chinese population.

Inclusion of individuals entering the medical insurance plan allows us to report on medical events and provide evidence of the diagnosis and treatment of various medical conditions to the Center for Medical Insurance, for the medical care services to be paid by the government. Thus, the diagnoses of events are based on clearly certified validated records that the patients attended the hospital. Also, all participants have a permanent personal registration number through which every medical event could be identified and information on medical history, drugs, and mortality could be recorded. Thus, the baseline data plus the follow-up data of every medical event could be identified over the observational period.

Sampling Method

The subjects have been continually entered into the governmental medical insurance plan since 2001. The medical insurance data were compiled in Oracle RDBMS 10g (Oracle Corporation). Structured Query Language and systematic sampling using randomization blocks enabled random sampling of the study population.

To achieve a representative sample reflecting longitudinal changes, the individuals in the medical plan were stated by calendar year. Then, a 5% sample of medical insurance data was selected randomly. Thus, a total of 1,228,639 people were selected. After excluding those with incomplete data (n = 2,611 cases) and readmission (n = 754,582), 471,446 cases were entered into the analysis. Among these, 1,237 patients with AF were identified, including 921 with newly diagnosed AF, thus providing 4,859 person-years of experience, and 316 who were re-hospitalized for AF (e-Fig 1). The Medical Ethics Committee of PLA General Hospital has been approved by the China Food and Drug Administration (registry number XZF20120145), and this ethics committee approved the present study (approval number 13BJZ40).

Evaluation of AF and Comorbidities

All individuals enrolled had a diagnosis of AF (International Classification of Diseases, Ninth Revision [ICD-9], or International Classification of Diseases, 10th Revision [ICD-10], codes 427.31 or I48). Information on comorbidities and events were also based on ICD-9 and ICD-10 codes. The index date was the first date of diagnosis of AF. Stroke and bleeding risks were assessed on the date of first diagnosis of AF.

AF was diagnosed based on an ECG or Holter recording. The inclusion criteria for an AF case was limited to inpatients with diagnosis of AF on admission and discharge. New-onset AF was defined as the individuals without AF at enrollment who subsequently developed AF after enrollment. To accurately verify the “true” patients with AF with a confirmed diagnosis, AF diagnosed at outpatient visits was excluded, as was atrial flutter. We excluded atrial flutter in this study because our focus was on the clinical epidemiology of AF specifically, and this would allow comparisons with other studies on the clinical epidemiology of AF in Western populations. For inpatients who had AF diagnosis on admission and discharge, the ECG could then be followed up to confirm the diagnosis of AF.

ICD-9 and ICD-10 codes for defined comorbidities are shown in e-Table 1. The definitions of various comorbidities are summarized in e-Table 2.

Stroke subtypes were classified into ischemic stroke (ICD-9 code 436, ICD-10 code I63) and hemorrhagic stroke (ICD-9 codes 430-432, ICD-10 codes I60.x, I61.x). Patients with major bleeding who required admission were identified. The major bleeding events were classed using ICD codes and medical data. Major bleeding was defined as an intracranial or extracranial hemorrhage or a decrease in the blood hemoglobin level of > 2.0 g/dL, the need for a transfusion of two or more units of blood, the need for surgery to achieve hemostasis, any combination of these events, or bleeding events needing in-hospital therapy.

Statistical Analysis

Continuous variables were tested for distribution by the Kolmogorov-Smirnov test. Those with a normal distribution were presented as a mean with SD and analyzed using the t test. Data with a non-normal distribution were presented as the median with interquartile range and were analyzed using the Mann-Whitney U test. The comparison of discrete variables was done via the χ2 test.

Antithrombotic drug use was calculated for stroke risk scores (CHADS2 and CHA2DS2-VASc [congestive heart failure, hypertension, age ≥ 75 years (doubled), diabetes, stroke or transient ischemic attack (doubled), vascular disease, age 65 to 74 years, and female sex]) and bleeding risk score (HAS-BLED [hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly (> 65 years), drugs/alcohol concomitantly]) for female and male subjects over time separately, and for different age categories (age 20-64 years, age 65-74 years, and age ≥ 75 years). Given that patients with AF in this cohort started receiving antithrombotic drugs in 2007, the average annual rate of change (or increase) in antithrombotic drug use for women and men was calculated by taking the mean difference in antithrombotic drug-use rates between consecutive years. P values for trend in anticoagulant use over time for women and men was calculated with the Jonckheere trend test.

The annual stroke and bleeding rates were calculated as the events by total number of patients with AF and by total person-years between 2001 and 2012, respectively. The annual stroke and bleeding rate estimates were also calculated for those not taking anticoagulant medication, and those taking aspirin and warfarin, between 2001 and 2012.

Multivariate analysis was used to assess anticoagulant use (ie, warfarin, aspirin) or no anticoagulant and the occurrence of stroke and major bleeding, respectively. Hazard ratios (HRs) of anticoagulant use for stroke were estimated by a Cox proportional hazard model that included anticoagulant drug as a time-dependent covariate and adjusted for baseline variables.

A sensitivity analysis of time trends of antithrombotic therapy with relation to stroke and bleeding events excluded patients with rheumatic heart disease and hyperthyroidism. To compare the time trends in anticoagulant use relative to stroke rates among Western and Chinese populations with AF, the various studies on AF were selected by region; that is, Europe, North America (specifically, the United States and Canada), international regions (including Asia), and China. The selected studies were those with large sample sizes (> 1,000 people), including data from Medicare claims, health insurance, veterans’ health records, and prospectively observational registries (ie, the National Cardiovascular Data Registry). Clinical trial cohorts were excluded, as they were unlikely to reflect real-world community populations, owing to restrictive trial eligibility criteria. The included studies are shown in e-Table 3). The overall trend line was drawn to roughly observe the changes in anticoagulant use over time among the different AF populations, compared with China.

A P value < .05 was considered statistically significant. The 95% CIs were calculated based on Poisson distribution. Statistical analysis was performed using IBM SPSS Statistics, version 21.0 (IBM).

There were 1,237 patients with AF identified in the 11-year period, with 921 cases of newly diagnosed AF (4,859 person-years) entered into the final analysis after excluding 316 cases of rehospitalization for AF. The mean age was 70 years among 921 patients with AF patients (62% men).

Most patients (n = 574, 62.3%) were not taking any antithrombotic agents. Three hundred forty-seven (37.7%) were receiving antithrombotic treatment: 298 (32.3%), aspirin; 38 (4.1%), warfarin; and 11 (1.2%), clopidogrel (Table 1).

Table Graphic Jump Location
TABLE 1 ]  Baseline Characteristics of 921 Patients With AF

Data given as No. (%) unless otherwise indicated. ACE = angiotensin-converting enzyme; AF = atrial fibrillation; ARB = angiotensin receptor blocker; ATT = antithrombotic treatment; CCB = calcium antagonist; CHADS2 = congestive heart failure, hypertension, age ≥ 75 y, diabetes, stroke (doubled); CHA2DS2-VASc = congestive heart failure, hypertension, age ≥ 75 y (doubled), diabetes, stroke or transient ischemic attack (doubled), vascular disease, age 65-74 years, and female sex; HAS-BLED = hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly (> 65 y), and concomitant drug (eg, aspirin, nonsteroidal antiinflammatory drugs) and alcohol use; IQR = interquartile range.

a 

Statistically significant at P < .05.

b 

Antacid drugs include H2-receptor antagonists and proton pump inhibitors.

Antithrombotic Treatment Related to Stroke or Bleeding Risk Scores

There were no significant differences in the CHADS2, CHA2DS2-VASc, and HAS-BLED scores between patients without antithrombotic treatment and patients with antithrombotic treatment (Table 1). When patients were classified by CHADS2 and CHA2DS2-VASc scores, the use of antithrombotic treatment did not increase with higher stroke risk scores (CHADS2 score, P = .522; CHA2DS2-VASc score, P = .957) (e-Fig 2). When bleeding risk was stratified by HAS-BLED score, the use of antithrombotic treatment was 23.0% in low-risk patients (0-1) and 28.0% in patients at intermediate (2) or high risk (≥ 3) (P = .095) (e-Fig 2).

Time Trends of Antithrombotic Treatment Related to Sex and Age

The use of antithrombotic treatment (mainly aspirin) increased in women and men over time, especially during the last 6 years. The rate of aspirin treatment increased from 4.0% in 2007 to 46.1% in 2012 in women, and from 7.7% in 2007 to 61.9% in 2012 in men. The rate of warfarin treatment rose from 4.4% in 2009 to 7.7% in 2012 in women, and from 4.3% in 2009 to 9.5% in 2012 in men (P value for trend for both, P < .005) (Fig 1). There was no significant difference in type of antithrombotic treatment between age groups (age 20-64 years, 65-74 years, and > 75 years, P = .361) (e-Fig 3).

Figure Jump LinkFigure 1 –  Time trends in antithrombotic treatment related to sex. ATT = antithrombotic treatment.Grahic Jump Location
Time Trends of Antithrombotic Treatment Related to Stroke and Bleeding Events

There were 59 ischemic strokes (6.4%) and 13 major bleeding events (1.4%), including seven hemorrhagic strokes, five GI hemorrhage, and one respiratory-related hemorrhage.

The rate of ischemic stroke was 6% in patients without antithrombotic treatment, 7% in patients taking aspirin, and 13% in patients taking warfarin over the studied decade. This translated to 0.01 person-years both in patients without antithrombotic treatment and those taking aspirin, and 0.02 person-years in patients taking warfarin (Table 2). Bleeding rates were 2% in patients without antithrombotic treatment over an 11-year period, 1% in those taking aspirin since 2007, and 3% in those on warfarin since 2009, which translates to 0.34 per 100 person-years without antithrombotic treatment, 0.16 per 100 person-years on aspirin, and 0.47 per 100 person-years on warfarin (Table 3).

Table Graphic Jump Location
TABLE 2 ]  Strokes Related to ATT in Patients With AF

See Table 1 legend for expansion of abbreviations.

Table Graphic Jump Location
TABLE 3 ]  Bleeding Events Related to ATT in Patients With AF

See Table 1 legend for expansion of abbreviations.

In the whole cohort, the annual stroke rate was approximately 6%, and annual rate of bleeding events was about 1% (e-Table 4). Time trends of stroke and bleeding events related to antithrombotic treatment are shown in Figure 2. Occurrences of both stroke and bleeding events increased over time, with bleeding rates increasing with the higher use of antithrombotic treatment.

Figure Jump LinkFigure 2 –  Time trends of ATT related to stroke and bleeding events in 921 patients with AF. AF = atrial fibrillation. See Figure 1 legend for expansion of other abbreviation.Grahic Jump Location
HR for the Risk of Stroke and Bleeding Events Associated With Antithrombotic Treatment

Using a Cox proportional hazard model, the HR (95% CI) for ischemic stroke in subjects not receiving antithrombotic treatment was 0.68 (0.39-1.18) compared with those taking aspirin and 1.39 (0.54-3.59) compared with those taking warfarin (e-Fig 4). A sensitivity analysis of time trends of antithrombotic therapy relative to stroke and bleeding events showed similar results, excluding people with rheumatic heart disease and hyperthyroidism (data not shown).

Comparisons With Europe and North America

A comparison of time trends in anticoagulant use related to stroke among Europe, North America, and China is shown in Figure 3. In more recent studies, use of oral anticoagulant drugs increased by approximately 20% in both Europe (eg, from 61% in Europe Heart Survey9 to 80% in the EuroObservational Research Program Atrial Fibrillation3) and North America (eg, from 30% in a Minnesota community-based study4 to 55% in the PINNACLE Registry2). In China, this increase is about 7%, based on hospital studies (eg, from 7% in a study by the Chinese Society of Cardiology10 to 14% in a study by Guo et al11), with warfarin use ranging from 3% to 14% in mainland China.1214 Oral anticoagulant use is much lower in China compared with North America and Europe, while stroke rates in the Chinese population with AF are much higher than in the population with AF in Western countries (Fig 3).

Figure Jump LinkFigure 3 –  Time trends in anticoagulant use and stroke rate in populations of patients with AF in Europe, North America, China, and in international studies. AFFECTS = Atrial Fibrillation Focus on Effective Clinical Treatment Strategies; EORP-AF = EuroObservational Research Program Atrial Fibrillation; GARFIELD = The Global Anticoagulant Registry in the Field; OAC = oral anticoagulant; PREFER in AF = Prevention of Thromboembolic Events, European Registry in Atrial Fibrillation; REACH = The Reduction of Atherothrombosis for Continued Health; RECORD AF = Registry on Cardiac Rhythm Disorders Assessing the Control of Atrial Fibrillation; RECORD AF-Asia Pacific = Registry on Cardiac Rhythm Disorders Assessing the Control of Atrial Fibrillation, Asia Pacific; TREAT-AF = The Retrospective Evaluation and Assessment of Therapies in AF study. See Figure 2 legend for expansion of other abbreviation.Grahic Jump Location

In this study, we show, first, that the use of antithrombotic treatment, mainly aspirin, has increased over the last decade in Chinese patients with newly diagnosed AF, but the annual stroke rate remains at about 6%. Second, the prescription of antithrombotic drugs had little relationship to stroke or bleeding risk scores, but anticoagulation rates were far lower than in patient populations with AF in Europe and North America. Third, bleeding risk increased with the increased use of antithrombotic treatment (eg, aspirin and warfarin) in this Chinese population. Fourth, neither aspirin nor warfarin adequately reduced stroke risk in this real-world population of Chinese patients with AF over the last decade, reflecting the inefficacy of aspirin and (likely) poor anticoagulation control among warfarin users.

In the early 2000s, reported warfarin use was only 0.5% to 9.1% in China, being 0.5% to 2.7% in community-based data and 6.6% to 9.1% according to hospital-based data.10,1214 The prevalence of stroke or TE was as high as 13.4% to 24.2% during the same time.10,1214 In the present community study, use of antithrombotic drugs (including warfarin) mainly increased in the late 2000s, but with an overall warfarin use of only 4% and the annual stroke rate still being 6%. Warfarin use was much higher in the hospital-based data compared with community-based data,15 but the underuse of warfarin was still common in China, as is seen in many Asian countries.5 On the other hand, aspirin is still overused in Chinese patients with AF, especially in the elderly population. In our previous hospital-based AF cohort, 60% of patients were on aspirin and only 14% patients were on warfarin. This was confirmed in a recent report of 9,727 Chinese patients with AF, which showed that 40% were taking aspirin compared with 20% taking warfarin.16 The high rate of aspirin use could reflect the fear of bleeding with warfarin, which is the main oral anticoagulant available in China.

To date, three international observational studies on AF have enrolled patients from Asian countries.1721 In these studies, about one-half of the patients with AF were given warfarin and the rates of warfarin use were much lower in the Asian subgroup with AF.17,18 Aspirin was still the common antithrombotic drug used. In the Registry on Cardiac Rhythm Disorders Assessing the Control of Atrial Fibrillation (RECORD-AF), in which 52% of patients were taking warfarin and 42%, aspirin, the Asian subgroup (RECORD-AF-Asia Pacific study) involved 2,721 patients (36% Chinese) and reported that 36% were on warfarin and 51% were on aspirin from 2007 to 2008.18 The difference in warfarin use in the RECORD-AF-Asia Pacific study and in this study could perhaps be related to prescribing habits (a province in China vs other Asia-Pacific countries with advanced health-care systems) or the data source, especially since RECORD-AF is an industry-funded commercial study and the present study is based on an administrative dataset. The rate of warfarin use in RECORD-AF-Asia Pacific probably represents the level of warfarin use in other Asian countries apart from China (ie, only 951 Chinese among the 2,629 Asian patients).18 Similarly, the Reduction of Atherothrombosis for Continued Health (REACH) Registry recruited 16% Asian and 0.1% Chinese patients.19 Among 4,582 patients with AF (90% of patients with CHADS2 score ≥ 1), the rate of warfarin use was 52% (including 16% taking warfarin plus an antiplatelet medication) and aspirin was used in 50%, with a 7.7% stroke rate over a 4-year follow-up.20 In the first cohort of 10,614 patients from 2009 to 2011, the Global Anticoagulant Registry in the Field (GARFIELD), included 24% Asians (0.7% Chinese) with newly diagnosed AF.21 Most of those patients were at moderate to high risk for TE (92% patients with CHADS2 score ≥ 1, 97% patients with CHA2DS2-VASc score ≥ 1), of whom 58% patients were on warfarin, and 14% of these patients had prior stroke or TIA.22

The relatively high rate of warfarin use in these international studies was more likely to be driven by the increased use (ie, > 20% in recent decades) of anticoagulant drugs in Europe and North America. Over recent decades, warfarin use has ranged from 40% to 83% in European countries, while the annual stroke rate was 1% to 5%2226 (e-Fig 5). Indeed, three AF surveys across European countries (Euro Heart Survey, EuroObservational Research Program Atrial Fibrillation, and the Prevention of Thromboembolic Events-European Registry in Atrial Fibrillation survey) confirmed a high overall rate of anticoagulant use in European clinical practice,3,9,27 achieving about 80% (6% to 8% patients on NOACs) more recently. Even so, prior stroke or TIA or thromboembolic event among these patients with AF remained at 10% to 15%.

Broadly, oral anticoagulant use was slightly lower in North America compared with Europe.2,2830 Nonetheless, compared with the Minnesota community-based study (1995-2000; warfarin used by 30% of patients), warfarin use increased by about 25% in the National Cardiovascular Data Registry PINNACLE Program (2008-2009; warfarin use by 50% of patients).4 Stroke rates in AF currently range from 0.5% to 2.0% in America.2,2729 However, the prevalence of stroke or TIA was still 7.7%, and was 1.3% for hemorrhagic stroke at primary cardiovascular hospitalization of patients newly diagnosed with AF.31 Similar anticoagulant use (32% in 1995; 60% in 2007) and stroke rate (1.7% in 1995; 2.1% in 2007) was seen in Canada.32,33

Antithrombotic therapy use (essentially warfarin and aspirin) increased in the late 2000s in China, with large variations across practice. However, aspirin (usually 100 mg) remains the common antithrombotic drug choice, and warfarin was widely underused in real-world practice in China. This low rate of warfarin use in Chinese patients with AF is similar to that seen in North America 20 years ago, and was far lower than that seen in European patients with AF. Moreover, the use of aspirin or warfarin did not reduce stroke risk in this real-world Chinese population with AF, while the bleeding risk did seemly increase, consistent with the findings of our previous hospital-based study on AF.15 The lack of aspirin efficacy is unsurprising, but the poor efficacy of warfarin in reducing stroke rates overall may reflect poor quality of anticoagulation control, given the need for regular anticoagulation monitoring to achieve a time in therapeutic range > 70%, which is hardly achieved in China.

Limitations

There are several limitations inherent to this observational study. First, health insurance data would likely result in an underestimate of AF if medical records were incomplete. The incidence of AF, together with that of stroke or major bleeding, also could have been underestimated without opportunistic screening for AF in this medical insurance database. We also identified patients with AF based on “objective” evidence (eg, ECG, 24-h Holter), which at least could be confirmed in the inpatients’ medical records. Indeed, we have not studied outpatients; we are less confident in the nonhospital diagnosis of AF for this group, as it may not be ECG verified, and AF diagnosis could possibly have been made clinically.

Second, there were 21 patients with rheumatic heart disease in this dataset, given it was a real-world investigation in China. While this could have an impact on the outcome, a sensitivity analysis excluding patients with rheumatic heart disease showed similar results. For the limited number of patients on oral anticoagulant therapy and small number of major bleeding events, we did not perform a Cox hazard model analysis to compare HRs of warfarin, aspirin, and nonanticoagulation on bleeding risk in this cohort. Also, the efficacy comparisons of warfarin, aspirin, and nonanticoagulation are limited by the nonrandomized comparisons, modest numbers, residual confounding from comorbidities, and lack of data on anticoagulation control (eg, time in therapeutic range values).3336 Finally, NOACs (initially dabigatran, followed by others) only became available in 2013 in China, and the present analysis does not address the impact of NOACs for stroke prevention in China.

Antithrombotic use, mainly aspirin, increased among Chinese patients newly diagnosed with AF, with no relationship to assessment of the patients’ stroke/bleeding risk. Oral anticoagulation use was very low. Given the health-care burden of AF and its complications, our study has major implications for health-care systems in non-Western countries, given the global burden of this common arrhythmia.

Author contributions: Y. G. and G. Y. H. L. had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Y. G. was principal author. Y. G. and G. Y. H. L. contributed to the study concept and data analyses and Y. G., H. W., Y. T., Y. W., and G. Y. H. L. contributed to drafting and revising the manuscript.

Financial/nonfinancial disclosures: The authors have reported to CHEST the following conflicts of interest: Dr Lip has served as a consultant for Bayer AG, Astellas Pharma Inc, Merck & Co Inc, Sanofi SA, Bristol-Myers Squibb/Pfizer Inc, Daiichi-Sankyo Co Ltd, Biotronik SE & Co KG, Portola Pharmaceuticals Inc, Medtronic Inc, and Boehringer Ingelheim GmbH and has been on the speaker’s bureau for Bayer AG, Bristol-Myers Squibb/Pfizer Inc, Boehringer Ingelheim GmbH, Daiichi-Sankyo Co Ltd, Medtronic Inc, and Sanofi Aventis LLC. Drs Guo, H. Wang, Tian, and Y. Wang have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Other contributions: We gratefully thank Zhang Wei, BD, Center for Medical Insurance, Human Resources and Social Security, Yunnan Province, for data collection and processing.

Additional information: The e-Figures and e-Tables can be found in the Supplemental Materials section of the online article.

AF

atrial fibrillation

CHADS2

congestive heart failure, hypertension, age ≥ 75 years, diabetes, stroke (doubled)

CHA2DS2-VASc

congestive heart failure, hypertension, age ≥ 75 years (doubled), diabetes, stroke or transient ischemic attack (doubled), vascular disease, age 65 to 74 years, and female sex

HAS-BLED

hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly (> 65 years), drugs/alcohol concomitantly

HR

hazard ratio

ICD-9

International Classification of Diseases, Ninth Revision

ICD-10

International Classification of Diseases, 10th Revision

NOAC

non-vitamin K antagonist oral anticoagulant

RECORD-AF

Registry on Cardiac Rhythm Disorders Assessing the Control of Atrial Fibrillation

TE

thromboembolism

TIA

transient ischemic attack

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Akao M, Chun YH, Wada H, et al; Fushimi AF Registry Investigators. Current status of clinical background of patients with atrial fibrillation in a community-based survey: the Fushimi AF Registry. J Cardiol. 2013;61(4):260-266. [CrossRef] [PubMed]
 
Guo Y, Wang H, Zhao X, et al. Relation of renal dysfunction to the increased risk of stroke and death in female patients with atrial fibrillation. Int J Cardiol. 2013;168(2):1502-1508. [CrossRef] [PubMed]
 
Hughes M, Lip GY; Guideline Development Group for the NICE national clinical guideline for management of atrial fibrillation in primary and secondary care. Risk factors for anticoagulation-related bleeding complications in patients with atrial fibrillation: a systematic review. QJM. 2007;100(10):599-607. [CrossRef] [PubMed]
 
Nieuwlaat R, Capucci A, Camm AJ, et al; European Heart Survey Investigators. Atrial fibrillation management: a prospective survey in ESC member countries: the Euro Heart Survey on Atrial Fibrillation. Eur Heart J. 2005;26(22):2422-2434. [CrossRef] [PubMed]
 
Society of Cardiology, Chinese Medical Association. Retrospective investigation of hospitalized patients with atrial fibrillation in mainland China. Chin Med J (Engl). 2004;117(12):1763-1767. [PubMed]
 
Guo Y, Apostolakis S, Blann AD, et al. Validation of contemporary stroke and bleeding risk stratification scores in non-anticoagulated Chinese patients with atrial fibrillation. Int J Cardiol. 2013;168(2):904-909. [CrossRef] [PubMed]
 
Zhou Z, Hu D. An epidemiological study on the prevalence of atrial fibrillation in the Chinese population of mainland China. J Epidemiol. 2008;18(5):209-216. [CrossRef] [PubMed]
 
Zhang X, Zhang S, Li Y, et al. Association of obesity and atrial fibrillation among middle-aged and elderly Chinese. Int J Obes (Lond). 2009;33(11):1318-1325. [CrossRef] [PubMed]
 
Sun Y, Hu D, Li K, Zhou Z. Predictors of stroke risk in native Chinese with nonrheumatic atrial fibrillation: retrospective investigation of hospitalized patients. Clin Cardiol. 2009;32(2):76-81. [CrossRef] [PubMed]
 
Guo Y, Pisters R, Apostolakis S, et al. Stroke risk and suboptimal thromboprophylaxis in Chinese patients with atrial fibrillation: would the novel oral anticoagulants have an impact? Int J Cardiol. 2013;168(1):515-522. [CrossRef] [PubMed]
 
Siu CW, Lip GY, Kwok-Fai Lam P, Tse HF. Risk of stroke and intracranial hemorrhage in 9,727 Chinese with atrial fibrillation in Hong Kong. Heart Rhythm. 2014;11(8):1401-1408. [CrossRef] [PubMed]
 
Camm AJ, Breithardt G, Crijns H, et al. Real-life observations of clinical outcomes with rhythm- and rate-control therapies for atrial fibrillation RECORDAF (Registry on Cardiac Rhythm Disorders Assessing the Control of Atrial Fibrillation). J Am Coll Cardiol. 2011;58(5):493-501. [CrossRef] [PubMed]
 
Amerena J, Chen SA, Sriratanasathavorn C, et al. Insights into management of atrial fibrillation in Asia Pacific gained from baseline data from REgistry on cardiac rhythm disORDers (RecordAF-Asia Pacific [AP]) registry. Am J Cardiol. 2012;109(3):378-382. [CrossRef] [PubMed]
 
Ohman EM, Bhatt DL, Steg PG, et al; REACH Registry Investigators. The REduction of Atherothrombosis for Continued Health (REACH) Registry: an international, prospective, observational investigation in subjects at risk for atherothrombotic events-study design. Am Heart J. 2006;151(4):786.e1-786.e10. [CrossRef]
 
Ruff CT, Bhatt DL, Steg PG, et al; REACH Registry Investigators. Long-term cardiovascular outcomes in patients with atrial fibrillation and atherothrombosis in the REACH Registry. Int J Cardiol. 2014;170(3):413-418. [CrossRef] [PubMed]
 
Kakkar AK, Mueller I, Bassand JP, et al; GARFIELD Registry Investigators. Risk profiles and antithrombotic treatment of patients newly diagnosed with atrial fibrillation at risk of stroke: perspectives from the international, observational, prospective GARFIELD registry. PLoS ONE. 2013;8(5):e63479. [CrossRef] [PubMed]
 
Friberg L, Benson L, Rosenqvist M, Lip GY. Assessment of female sex as a risk factor in atrial fibrillation in Sweden: nationwide retrospective cohort study. BMJ. 2012;344:e3522. [CrossRef] [PubMed]
 
Bosch RF, Kirch W, Theuer JD, et al. Atrial fibrillation management, outcomes and predictors of stable disease in daily practice: prospective non-interventional study. Int J Cardiol. 2013;167(3):750-756. [CrossRef] [PubMed]
 
Rietbrock S, Heeley E, Plumb J, van Staa T. Chronic atrial fibrillation: incidence, prevalence, and prediction of stroke using the congestive heart failure, hypertension, age >75, diabetes mellitus, and prior stroke or transient ischemic attack (CHADS2) risk stratification scheme. Am Heart J. 2008;156(1):57-64. [CrossRef] [PubMed]
 
Andersson P, Löndahl M, Abdon NJ, Terent A. The prevalence of atrial fibrillation in a geographically well-defined population in northern Sweden: implications for anticoagulation prophylaxis. J Intern Med. 2012;272(2):170-176. [CrossRef] [PubMed]
 
Cohen A, Dallongeville J, Durand-Zaleski I, Bouée S, Le Heuzey JY; EPHA Investigators. Characteristics and management of outpatients with history of or current atrial fibrillation: the observational French EPHA study. Arch Cardiovasc Dis. 2010;103(6-7):376-387. [CrossRef] [PubMed]
 
Kirchhof P, Ammentorp B, Darius H, et al. Management of atrial fibrillation in seven European countries after the publication of the 2010 ESC Guidelines on atrial fibrillation: primary results of the PREvention oF thromboemolic events—European Registry in Atrial Fibrillation (PREFER in AF). Europace. 2014;16(1):6-14. [CrossRef] [PubMed]
 
Walker AM, Bennett D. Epidemiology and outcomes in patients with atrial fibrillation in the United States. Heart Rhythm. 2008;5(10):1365-1372. [CrossRef] [PubMed]
 
Reiffel JA, Kowey PR, Myerburg R, et al; AFFECTS Scientific Advisory Committee and Investigators. Practice patterns among United States cardiologists for managing adults with atrial fibrillation (from the AFFECTS Registry). Am J Cardiol. 2010;105(8):1122-1129. [CrossRef] [PubMed]
 
Turakhia MP, Hoang DD, Xu X, et al. Differences and trends in stroke prevention anticoagulation in primary care vs cardiology specialty management of new atrial fibrillation: The Retrospective Evaluation and Assessment of Therapies in AF (TREAT-AF) study. Am Heart J. 2013;165(1):93-101. [CrossRef] [PubMed]
 
Turakhia MP, Solomon MD, Jhaveri M, et al. Burden, timing, and relationship of cardiovascular hospitalization to mortality among Medicare beneficiaries with newly diagnosed atrial fibrillation. Am Heart J. 2013;166(3):573-580. [CrossRef] [PubMed]
 
Kerr CR, Humphries KH, Talajic M, Klein GJ, Connolly SJ, Green M. The Canadian registry of atrial fibrillation: a noninterventional follow-up of patients after the first diagnosis of atrial fibrillation. Am J Cardiol. 1998;82(8A):82N-85N. [CrossRef] [PubMed]
 
Tsadok MA, Jackevicius CA, Essebag V, et al. Rhythm versus rate control therapy and subsequent stroke or transient ischemic attack in patients with atrial fibrillation. Circulation. 2012;126(23):2680-2687. [CrossRef] [PubMed]
 
Gallego P, Roldan V, Marin F, et al. Cessation of oral anticoagulation in relation to mortality and the risk of thrombotic events in patients with atrial fibrillation. Thromb Haemost. 2013;110(6):1189-1198. [CrossRef] [PubMed]
 
De Caterina R, Husted S, Wallentin L, et al. Vitamin K antagonists in heart disease: current status and perspectives (section III). Position paper of the ESC Working Group on Thrombosis—Task Force on Anticoagulants in Heart Disease. Thromb Haemost. 2013;110(6):1087-1107. [CrossRef] [PubMed]
 
De Caterina R, Husted S, Wallentin L, et al; European Society of Cardiology Working Group on Thrombosis Task Force on Anticoagulants in Heart Disease. General mechanisms of coagulation and targets of anticoagulants (section I). Position paper of the ESC Working Group on Thrombosis–Task Force on Anticoagulants in Heart Disease. Thromb Haemost. 2013;109(4):569-579. [CrossRef] [PubMed]
 

Figures

Figure Jump LinkFigure 1 –  Time trends in antithrombotic treatment related to sex. ATT = antithrombotic treatment.Grahic Jump Location
Figure Jump LinkFigure 2 –  Time trends of ATT related to stroke and bleeding events in 921 patients with AF. AF = atrial fibrillation. See Figure 1 legend for expansion of other abbreviation.Grahic Jump Location
Figure Jump LinkFigure 3 –  Time trends in anticoagulant use and stroke rate in populations of patients with AF in Europe, North America, China, and in international studies. AFFECTS = Atrial Fibrillation Focus on Effective Clinical Treatment Strategies; EORP-AF = EuroObservational Research Program Atrial Fibrillation; GARFIELD = The Global Anticoagulant Registry in the Field; OAC = oral anticoagulant; PREFER in AF = Prevention of Thromboembolic Events, European Registry in Atrial Fibrillation; REACH = The Reduction of Atherothrombosis for Continued Health; RECORD AF = Registry on Cardiac Rhythm Disorders Assessing the Control of Atrial Fibrillation; RECORD AF-Asia Pacific = Registry on Cardiac Rhythm Disorders Assessing the Control of Atrial Fibrillation, Asia Pacific; TREAT-AF = The Retrospective Evaluation and Assessment of Therapies in AF study. See Figure 2 legend for expansion of other abbreviation.Grahic Jump Location

Tables

Table Graphic Jump Location
TABLE 1 ]  Baseline Characteristics of 921 Patients With AF

Data given as No. (%) unless otherwise indicated. ACE = angiotensin-converting enzyme; AF = atrial fibrillation; ARB = angiotensin receptor blocker; ATT = antithrombotic treatment; CCB = calcium antagonist; CHADS2 = congestive heart failure, hypertension, age ≥ 75 y, diabetes, stroke (doubled); CHA2DS2-VASc = congestive heart failure, hypertension, age ≥ 75 y (doubled), diabetes, stroke or transient ischemic attack (doubled), vascular disease, age 65-74 years, and female sex; HAS-BLED = hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly (> 65 y), and concomitant drug (eg, aspirin, nonsteroidal antiinflammatory drugs) and alcohol use; IQR = interquartile range.

a 

Statistically significant at P < .05.

b 

Antacid drugs include H2-receptor antagonists and proton pump inhibitors.

Table Graphic Jump Location
TABLE 2 ]  Strokes Related to ATT in Patients With AF

See Table 1 legend for expansion of abbreviations.

Table Graphic Jump Location
TABLE 3 ]  Bleeding Events Related to ATT in Patients With AF

See Table 1 legend for expansion of abbreviations.

References

Chugh SS, Havmoeller R, Narayanan K, et al. Worldwide epidemiology of atrial fibrillation: a global burden of disease 2010 study. Circulation. 2013;129(8):837-847. [CrossRef] [PubMed]
 
Chan PS, Maddox TM, Tang F, Spinler S, Spertus JA. Practice-level variation in warfarin use among outpatients with atrial fibrillation (from the NCDR PINNACLE program). Am J Cardiol. 2011;108(8):1136-1140. [CrossRef] [PubMed]
 
Lip GY, Laroche C, Dan GA, et al. A prospective survey in European Society of Cardiology member countries of atrial fibrillation management: baseline results of EuroObservational Research Programme Atrial Fibrillation (EORP-AF) Pilot General Registry. Europace. 2013;16(3):308-319. [CrossRef] [PubMed]
 
Miyasaka Y, Barnes ME, Gersh BJ, et al. Time trends of ischemic stroke incidence and mortality in patients diagnosed with first atrial fibrillation in 1980 to 2000: report of a community-based study. Stroke. 2005;36(11):2362-2366. [CrossRef] [PubMed]
 
Lip GY, Brechin CM, Lane DA. The global burden of atrial fibrillation and stroke: a systematic review of the epidemiology of atrial fibrillation in regions outside North America and Europe. Chest. 2012;142(6):1489-1498. [CrossRef] [PubMed]
 
Akao M, Chun YH, Wada H, et al; Fushimi AF Registry Investigators. Current status of clinical background of patients with atrial fibrillation in a community-based survey: the Fushimi AF Registry. J Cardiol. 2013;61(4):260-266. [CrossRef] [PubMed]
 
Guo Y, Wang H, Zhao X, et al. Relation of renal dysfunction to the increased risk of stroke and death in female patients with atrial fibrillation. Int J Cardiol. 2013;168(2):1502-1508. [CrossRef] [PubMed]
 
Hughes M, Lip GY; Guideline Development Group for the NICE national clinical guideline for management of atrial fibrillation in primary and secondary care. Risk factors for anticoagulation-related bleeding complications in patients with atrial fibrillation: a systematic review. QJM. 2007;100(10):599-607. [CrossRef] [PubMed]
 
Nieuwlaat R, Capucci A, Camm AJ, et al; European Heart Survey Investigators. Atrial fibrillation management: a prospective survey in ESC member countries: the Euro Heart Survey on Atrial Fibrillation. Eur Heart J. 2005;26(22):2422-2434. [CrossRef] [PubMed]
 
Society of Cardiology, Chinese Medical Association. Retrospective investigation of hospitalized patients with atrial fibrillation in mainland China. Chin Med J (Engl). 2004;117(12):1763-1767. [PubMed]
 
Guo Y, Apostolakis S, Blann AD, et al. Validation of contemporary stroke and bleeding risk stratification scores in non-anticoagulated Chinese patients with atrial fibrillation. Int J Cardiol. 2013;168(2):904-909. [CrossRef] [PubMed]
 
Zhou Z, Hu D. An epidemiological study on the prevalence of atrial fibrillation in the Chinese population of mainland China. J Epidemiol. 2008;18(5):209-216. [CrossRef] [PubMed]
 
Zhang X, Zhang S, Li Y, et al. Association of obesity and atrial fibrillation among middle-aged and elderly Chinese. Int J Obes (Lond). 2009;33(11):1318-1325. [CrossRef] [PubMed]
 
Sun Y, Hu D, Li K, Zhou Z. Predictors of stroke risk in native Chinese with nonrheumatic atrial fibrillation: retrospective investigation of hospitalized patients. Clin Cardiol. 2009;32(2):76-81. [CrossRef] [PubMed]
 
Guo Y, Pisters R, Apostolakis S, et al. Stroke risk and suboptimal thromboprophylaxis in Chinese patients with atrial fibrillation: would the novel oral anticoagulants have an impact? Int J Cardiol. 2013;168(1):515-522. [CrossRef] [PubMed]
 
Siu CW, Lip GY, Kwok-Fai Lam P, Tse HF. Risk of stroke and intracranial hemorrhage in 9,727 Chinese with atrial fibrillation in Hong Kong. Heart Rhythm. 2014;11(8):1401-1408. [CrossRef] [PubMed]
 
Camm AJ, Breithardt G, Crijns H, et al. Real-life observations of clinical outcomes with rhythm- and rate-control therapies for atrial fibrillation RECORDAF (Registry on Cardiac Rhythm Disorders Assessing the Control of Atrial Fibrillation). J Am Coll Cardiol. 2011;58(5):493-501. [CrossRef] [PubMed]
 
Amerena J, Chen SA, Sriratanasathavorn C, et al. Insights into management of atrial fibrillation in Asia Pacific gained from baseline data from REgistry on cardiac rhythm disORDers (RecordAF-Asia Pacific [AP]) registry. Am J Cardiol. 2012;109(3):378-382. [CrossRef] [PubMed]
 
Ohman EM, Bhatt DL, Steg PG, et al; REACH Registry Investigators. The REduction of Atherothrombosis for Continued Health (REACH) Registry: an international, prospective, observational investigation in subjects at risk for atherothrombotic events-study design. Am Heart J. 2006;151(4):786.e1-786.e10. [CrossRef]
 
Ruff CT, Bhatt DL, Steg PG, et al; REACH Registry Investigators. Long-term cardiovascular outcomes in patients with atrial fibrillation and atherothrombosis in the REACH Registry. Int J Cardiol. 2014;170(3):413-418. [CrossRef] [PubMed]
 
Kakkar AK, Mueller I, Bassand JP, et al; GARFIELD Registry Investigators. Risk profiles and antithrombotic treatment of patients newly diagnosed with atrial fibrillation at risk of stroke: perspectives from the international, observational, prospective GARFIELD registry. PLoS ONE. 2013;8(5):e63479. [CrossRef] [PubMed]
 
Friberg L, Benson L, Rosenqvist M, Lip GY. Assessment of female sex as a risk factor in atrial fibrillation in Sweden: nationwide retrospective cohort study. BMJ. 2012;344:e3522. [CrossRef] [PubMed]
 
Bosch RF, Kirch W, Theuer JD, et al. Atrial fibrillation management, outcomes and predictors of stable disease in daily practice: prospective non-interventional study. Int J Cardiol. 2013;167(3):750-756. [CrossRef] [PubMed]
 
Rietbrock S, Heeley E, Plumb J, van Staa T. Chronic atrial fibrillation: incidence, prevalence, and prediction of stroke using the congestive heart failure, hypertension, age >75, diabetes mellitus, and prior stroke or transient ischemic attack (CHADS2) risk stratification scheme. Am Heart J. 2008;156(1):57-64. [CrossRef] [PubMed]
 
Andersson P, Löndahl M, Abdon NJ, Terent A. The prevalence of atrial fibrillation in a geographically well-defined population in northern Sweden: implications for anticoagulation prophylaxis. J Intern Med. 2012;272(2):170-176. [CrossRef] [PubMed]
 
Cohen A, Dallongeville J, Durand-Zaleski I, Bouée S, Le Heuzey JY; EPHA Investigators. Characteristics and management of outpatients with history of or current atrial fibrillation: the observational French EPHA study. Arch Cardiovasc Dis. 2010;103(6-7):376-387. [CrossRef] [PubMed]
 
Kirchhof P, Ammentorp B, Darius H, et al. Management of atrial fibrillation in seven European countries after the publication of the 2010 ESC Guidelines on atrial fibrillation: primary results of the PREvention oF thromboemolic events—European Registry in Atrial Fibrillation (PREFER in AF). Europace. 2014;16(1):6-14. [CrossRef] [PubMed]
 
Walker AM, Bennett D. Epidemiology and outcomes in patients with atrial fibrillation in the United States. Heart Rhythm. 2008;5(10):1365-1372. [CrossRef] [PubMed]
 
Reiffel JA, Kowey PR, Myerburg R, et al; AFFECTS Scientific Advisory Committee and Investigators. Practice patterns among United States cardiologists for managing adults with atrial fibrillation (from the AFFECTS Registry). Am J Cardiol. 2010;105(8):1122-1129. [CrossRef] [PubMed]
 
Turakhia MP, Hoang DD, Xu X, et al. Differences and trends in stroke prevention anticoagulation in primary care vs cardiology specialty management of new atrial fibrillation: The Retrospective Evaluation and Assessment of Therapies in AF (TREAT-AF) study. Am Heart J. 2013;165(1):93-101. [CrossRef] [PubMed]
 
Turakhia MP, Solomon MD, Jhaveri M, et al. Burden, timing, and relationship of cardiovascular hospitalization to mortality among Medicare beneficiaries with newly diagnosed atrial fibrillation. Am Heart J. 2013;166(3):573-580. [CrossRef] [PubMed]
 
Kerr CR, Humphries KH, Talajic M, Klein GJ, Connolly SJ, Green M. The Canadian registry of atrial fibrillation: a noninterventional follow-up of patients after the first diagnosis of atrial fibrillation. Am J Cardiol. 1998;82(8A):82N-85N. [CrossRef] [PubMed]
 
Tsadok MA, Jackevicius CA, Essebag V, et al. Rhythm versus rate control therapy and subsequent stroke or transient ischemic attack in patients with atrial fibrillation. Circulation. 2012;126(23):2680-2687. [CrossRef] [PubMed]
 
Gallego P, Roldan V, Marin F, et al. Cessation of oral anticoagulation in relation to mortality and the risk of thrombotic events in patients with atrial fibrillation. Thromb Haemost. 2013;110(6):1189-1198. [CrossRef] [PubMed]
 
De Caterina R, Husted S, Wallentin L, et al. Vitamin K antagonists in heart disease: current status and perspectives (section III). Position paper of the ESC Working Group on Thrombosis—Task Force on Anticoagulants in Heart Disease. Thromb Haemost. 2013;110(6):1087-1107. [CrossRef] [PubMed]
 
De Caterina R, Husted S, Wallentin L, et al; European Society of Cardiology Working Group on Thrombosis Task Force on Anticoagulants in Heart Disease. General mechanisms of coagulation and targets of anticoagulants (section I). Position paper of the ESC Working Group on Thrombosis–Task Force on Anticoagulants in Heart Disease. Thromb Haemost. 2013;109(4):569-579. [CrossRef] [PubMed]
 
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