Chest
Volume 137, Issue 2, February 2010, Pages 263-272
Journal home page for Chest

Original Research
Thromboembolism
Refining Clinical Risk Stratification for Predicting Stroke and Thromboembolism in Atrial Fibrillation Using a Novel Risk Factor-Based Approach: The Euro Heart Survey on Atrial Fibrillation

https://doi.org/10.1378/chest.09-1584Get rights and content

Background

Contemporary clinical risk stratification schemata for predicting stroke and thromboembolism (TE) in patients with atrial fibrillation (AF) are largely derived from risk factors identified from trial cohorts. Thus, many potential risk factors have not been included.

Methods

We refined the 2006 Birmingham/National Institute for Health and Clinical Excellence (NICE) stroke risk stratification schema into a risk factor-based approach by reclassifying and/or incorporating additional new risk factors where relevant. This schema was then compared with existing stroke risk stratification schema in a real-world cohort of patients with AF (n = 1,084) from the Euro Heart Survey for AF.

Results

Risk categorization differed widely between the different schemes compared. Patients classified as high risk ranged from 10.2% with the Framingham schema to 75.7% with the Birmingham 2009 schema. The classic CHADS2 (Congestive heart failure, Hypertension, Age > 75, Diabetes, prior Stroke/transient ischemic attack) schema categorized the largest proportion (61.9%) into the intermediate-risk strata, whereas the Birmingham 2009 schema classified 15.1% into this category. The Birmingham 2009 schema classified only 9.2% as low risk, whereas the Framingham scheme categorized 48.3% as low risk. Calculated C-statistics suggested modest predictive value of all schema for TE. The Birmingham 2009 schema fared marginally better (C-statistic, 0.606) than CHADS2. However, those classified as low risk by the Birmingham 2009 and NICE schema were truly low risk with no TE events recorded, whereas TE events occurred in 1.4% of low-risk CHADS2 subjects. When expressed as a scoring system, the Birmingham 2009 schema (CHA2DS2-VASc acronym) showed an increase in TE rate with increasing scores (P value for trend = .003).

Conclusions

Our novel, simple stroke risk stratification schema, based on a risk factor approach, provides some improvement in predictive value for TE over the CHADS2 schema, with low event rates in low-risk subjects and the classification of only a small proportion of subjects into the intermediate-risk category. This schema could improve our approach to stroke risk stratification in patients with AF.

Section snippets

Validation Cohort

To test the predictive ability of the refined Birmingham schema, and to compare this with the performance of other schema, we used the Euro Heart Survey on AF population. Survey methods, center participation, patient characteristics, management and definitions of the baseline and follow-up survey of the Euro Heart Survey on AF have previously been described.21, 22 In summary, 5,333 ambulant and hospitalized patients with AF were enrolled from the cardiology practices of 182 hospitals among 35

Results

The 1,084 patients with nonvalvular AF, who were not on anticoagulation at baseline and for whom we knew TE status at 1 year, were on average 66 years old and 40.8% were women (Table 3). Hypertension was the most prevalent stroke risk factor (67.3%), followed by coronary artery disease (38.4%). Antiplatelet drugs were taken by 74.0%. In univariate analyses, female gender, history of vascular disease, prior stroke/TIA, and diabetes were associated with an increased incidence of TE (all P < .05;

Discussion

In this article, we have provided a validation for a novel risk factor-based approach to stroke risk stratification (Birmingham 2009), in comparison with other published schema, in a real world European cohort. This Birmingham 2009 schema considers patients with a prior stroke/TIA or patients ≥ 75 years as high risk and as candidates for warfarin. Furthermore, a combination of at least two risk factors from hypertension, heart failure, diabetes, age 65 to 75, female gender, and vascular disease

Acknowledgments

Author contributions: Dr Lip: contributed to study design and hypothesis, data interpretation, and drafting and revisions of the manuscript.

Dr Nieuwlaat: contributed to statistical analyses, data interpretation, and drafting of the manuscript.

Dr Pisters: contributed to drafting and revision of the manuscript.

Dr Lane: contributed to drafting and revision of the manuscript.

Dr Crijns: contributed to drafting and revision of the manuscript.

Financial/nonfinancial disclosures: The authors have

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  • Cited by (0)

    Funding/Support: The Euro Heart Survey is funded by industry sponsors AstraZeneca, Sanofi-Aventis, and Eucomed, and by the Austrian Heart Foundation, Austrian Society of Cardiology, French Federation of Cardiology, Hellenic Cardiological Society, Netherlands Heart Foundation, Portuguese Society of Cardiology, Spanish Cardiac Society, Swedish Heart and Lung Foundation and individual centers.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).

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