Stroke prevention with appropriate use of antithrombotic therapy remains absolutely central to the overall management strategy of patients with atrial fibrillation (AF).

The first consideration is stroke risk assessment. Various risk factors have been used to derive stroke risk stratification schema, which have ‘artificially’ categorised patients into low, moderate and high risk stroke strata, so that the patients at highest risk can be identified for warfarin therapy. Many of these risk factors were derived from the non-warfarin arms of the historical trial cohorts, where only <10% of patients screened were randomised, and many risk factors were not systematically looked for, nor consistently defined. With the availability of the novel oral anticoagulants that are alternatives to warfarin, there is the need to be more inclusive of common stroke risk factors, to focus more on identification of ‘truly low risk patients’ with AF who do not need any antithrombotic therapy.

Indeed, the 2012 focused update to the European Society of Cardiology (ESC) guidelines recommends stroke risk assessment using the CHA2DS2-VASc score,¹ and strongly emphasises a clinical practice shift towards much more focus on defining the ‘truly low-risk’ patients with AF, instead of trying to identify ‘high-risk’ patients. These ‘truly low risk’ patients are those patients who fulfil the criteria of ‘age < 65 and lone AF (irrespective of gender) or CHA2DS2-VASc score=0’, who do not need any antithrombotic therapy).

The second aspect with regard to thromboprophylaxis is to assess bleeding risk.² The HAS-BLED score is the recommended score in the ESC and Canadian guidelines for this purpose.^1,3 HAS-BLED has been well validated,^4-6 and has been shown to outperform other risk scores (including HEMORR(2)HAGES and ATRIA) in predicting clinically relevant bleeding.^7-9 Indeed, limitations of some prior scores have previously been highlighted.¹⁰ Also, HAS-BLED has good predictive value for intracranial bleeding, whilst other scores (e.g. ATRIA) were not predictive.⁷ In the Swedish AF Cohort study, the rates of major bleeding (and intracranial bleeding) increased with increasing HAS-BLED score, but rates were fairly similar for warfarin and aspirin treated patients.¹¹

How to use HAS-BLED? A high HAS-BLED score (≥3) is indicative of the need for regular clinical review and followup, but should not be used per se as a reason for stopping oral anticoagulation.¹ Indeed, a high HAS-BLED score allows the clinician to ‘flag up’ patients at potential risk for serious bleeding in an informed manner, rather than relying on guesswork. The latter may be dangerous, as it has been shown that clinicians are poor in estimating bleeding risk.¹²

The HAS-BLED score also makes clinicians think about the potentially reversible risk factors for bleeding, e.g. uncontrolled blood pressure (the H in HAS-BLED), labile INRs if on warfarin (the L in HAS-BLED) and concomitant use of aspirin/NSAIDs (the D in HAS-BLED). The HAS-BLED score is also predictive of major bleeding in patients (both AF and non-AF) undergoing bridging therapy.¹³

Bleeding risk and stroke risk are closely related. Those patients with AF and a high HAS-BLED score derive a higher net clinical benefit from oral anticoagulation when balancing ischaemic stroke against intracranial bleeding.^14,15 This is irrespective of stroke risk strata, whether assessed by CHADS2 or CHA2DS2-VASc, with the exception of CHA2DS2-VASc score=0, where the net clinical benefit was negative reflecting the ‘truly low risk’ status of such patients that would result in a net disadvantage of warfarin therapy; of note, there was no stroke risk or HAS-BLED strata showing any positive net clinical benefit for aspirin.¹⁴

An illustrative application of the CHA2DS2-VASc and HAS-BLED scores to aid decision making has recently been published (Table 1).¹⁶

References

1. Camm, AJ, Lip GY, De Caterina R, et al. 2012 focused update of the ESC Guidelines for the management of atrial fibrillation: An update of the 2010 ESC Guidelines for the management of atrial fibrillation. Eur Heart J 2012. [Epub ahead ofprint] PubMed PMID: 22922413
2. Lip GY, Andreotti F, Fauchier L, et al. Bleeding risk assessment and management in atrial fibrillation patients. Executive Summary of a Position Document from the European Heart Rhythm Association [EHRA], endorsed by the European Society of Cardiology [ESC] Working Group on Thrombosis. Thromb Haemost 2011;106:997-1011.
3. Skanes AC, Healey JS, Cairns JA, et al. Focused 2012 update of the Canadian Cardiovascular Societyatrial fibrillation guidelines: recommendations for stroke
4. Pisters R, Lane DA, Nieuwlaat R, de Vos CB, Crijns HJGM, Lip GYH. A novel user-friendly score (HAS-BLED) to assess one year risk of major bleeding in atrial fibrillation patients: The Euro Heart Survey. Chest 2010;138:1093-100.
5. Lip GY, Frison L, Halperin JL, Lane D. Comparative Validation of a Novel Risk Score for Predicting Bleeding Risk in Anticoagulated Patients With Atrial Fibrillation. The HAS-BLED (Hypertension, Abnormal Renal/Liver Function, Stroke, Bleeding History or Predisposition, Labile INR, Elderly, Drugs/Alcohol Concomitantly) Score. J Am Coll Cardiol 2011;57:173-80.
6. Olesen JB, Lip GY, Hansen PR, et al. Bleeding risk in 'real world' patients with atrial fibrillation: comparison of two established bleeding prediction schemes in a nationwide cohort. J Thromb Haemost 2011;9:1460-7.
7. Apostolakis S, Lane D, Gao Y, Buller H, Lip GY. Performance of the HEMORR2HAGES, ATRIA and HAS-BLED bleeding risk prediction scores in anticoagulated patients with atrial fibrillation: The AMADEUS study. J Am Coll Cardiol 2012;60:861-867.
8. Roldán V, Marín F, Fernández H, et al. Predictive value of the HAS-BLED and ATRIA bleeding scores for the risk of serious bleeding in a 'real world' anticoagulated atrial fibrillation population. Chest 2012. [Epub ahead of print] DOI 10.1378/chest.12-0608 PubMed PMID: 22722228.
9. Lip GY, Banerjee A, Lagrenade I, Lane DA, Taillandier S, Fauchier L. Assessing the Risk of Bleeding in Patients with Atrial Fibrillation: The Loire Valley Atrial Fibrillation Project. Circ Arrhythm Electrophysiol 2012. [Epub ahead of print] PubMed PMID: 22923275.
10. Olesen JB, Pisters R, Roldans V, Marin F, Lane DA. The ATRIA Risk Scheme to Predict Warfarin-Associated Hemorrhage: Not Ready for Clinical Use. J Am Coll Cardiol 2012;59;194-195.
11. Friberg L, Rosenqvist M, Lip GYH. Evaluation of risk stratification schemes for ischemic stroke and bleeding in 182,678 patients with atrial fibrillation: The Swedish Atrial Fibrillation cohort study. Eur Heart J 2012;33:1500-10.
12. Lip GY, Zarifis J, Watson RD, Beevers DG. Physician variation in the management of patients with atrial fibrillation. Heart 1996;75:200-5.
13. Omran H, Bauersachs R, Rübenacker S, Goss F, Hammerstingl C. The HAS-BLED score predicts bleedings during bridging of chronic oral anticoagulation. Results from the national multicentre BNK Online bRiDging REgistRy (BORDER). Thromb Haemost 2012;108:65-7.
14. Olesen JB, Lip GY, Lindhardsen J, et al. Risks of thromboembolism and bleeding with thromboprophylaxis in patients with atrial fibrillation: A net clinical benefit analysis using a 'real world' nationwide cohort study. Thromb Haemost 2011;106:739-49.
15. Friberg L, Rosenqvist M, Lip GY. Net clinical benefit of warfarin in patients with atrial fibrillation: a report from the Swedish atrial fibrillation cohort study. Circulation 2012;125:2298-30.
16. Lane DA, Lip GY. Use of the CHA2DS2-VASc and HAS-BLED Scores to Aid Decision Making for Thromboprophylaxis in Nonvalvular Atrial Fibrillation. Circulation 2012;126:860-5.

Keywords: Anticoagulants, Aspirin, Atrial Fibrillation, Blood Pressure, Intracranial Hemorrhages, Risk Assessment, Risk Factors, Stroke, Warfarin

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