Key points

  • Safe and effective anticoagulation for stroke prevention in patients with non-valvular atrial fibrillation (NVAF) relies on balancing the benefits of blood clot prevention with the risks of bleeding.
  • Clinical risk scores can help with the initial decision on whether to anticoagulate a patient or not.
  • The CHA2DS2-VASc and HAS-BLED scores are well established for evaluating stroke risk for patients with atrial fibrillation (AF) and bleeding risk, respectively.
  • Oral anticoagulation is recommended for patients with a CHA2DS2-VASc score of ≥ 2 (men) or ≥ 3 (women).
  • A HAS-BLED score of ≥ 3 indicates a high risk of bleeding – regular review and treatment of modifiable bleeding risk factors is recommended for these patients, rather than avoidance of oral anticoagulation.
  • Some patients may accept a higher risk of bleeding, knowing that they are avoiding a stroke.

Balancing stroke and bleeding risk

Four oral anticoagulants are PBS-listed for the prevention of stroke and systemic embolism in adults with NVAF and one additional risk factor for stroke.1-5

These are warfarin, and three non-vitamin K antagonist oral anticoagulants: apixaban (Eliquis), dabigatran (Pradaxa) and rivaroxaban (Xarelto).1-5

Safe and effective treatment relies on balancing the benefits of blood clot prevention with the risks of bleeding – whichever anticoagulant is selected as the most appropriate medicine for an individual patient.

Clinical risk scores to stratify patients according to their stroke or bleeding risk can help with the initial decision on whether to anticoagulate a patient or not, and help identify modifiable risk factors for bleeding.6

A number of risk factors can be used to estimate stroke risk, several different bleeding risk scores have been developed, and stroke and bleeding risk factors can overlap.6

However, the CHA2DS2-VASc and HAS-BLED scores are well established for stroke risk in patients with AF and bleeding risk, respectively, and are recommended in current AF guidelines.6-8 

Predicting stroke risk

Guidelines recommend the CHA2DS2-VASc score for the prediction of stroke risk in patients with NVAF (see Table 1).6

The CHA2DS2-VASc score was developed to overcome limitations of the simpler CHADS2 score, including the grouping together of patients with different levels of risk and underestimation of stroke risk.8,9

Increasing CHA2DS2-VASc score has been associated with increasing risk of stroke or other thromboembolic events, with a theoretical untreated rate over 1 year of 1.3, 2.2 and 3.2 for a score of 1, 2 and 3, respectively.10

Using the CHA2DS2-VASc score:6

  • Score ≥ 2 (men) or ≥ 3 (women) = Oral anticoagulation is recommended
  • Score 1 (men) or 2 (women) = Oral anticoagulation can be considered, based on individual patient characteristics and preferences
  • Score 0 (no clinical risk factors) = No anticoagulation (or antiplatelet medicine) is required.

When interpreting results, the relative weighting of individual risk factors and patient preferences should still be considered, especially in patients with only a single risk factor (besides female sex).6

For example, advancing age is associated with other stroke risk factors (such as heart failure), whereas female sex alone does not increase stroke risk in the absence of other risk factors.6

Note that, due to limited evidence, antiplatelet medicines are not recommend for stroke prevention in AF, irrespective of stroke risk.6


Table 1: CHA2DS2-VASc clinical score for risk of stroke, transient ischaemic attach or systemic embolism6,9
Risk factor Score
Congestive heart failure

Signs/symptoms of heart failure or objective evidence of reduced left-ventricular ejection fraction


1
Hypertension

Resting blood pressure > 140/90 mmHg on ≥ 2 occasions, or current antihypertensive treatment


1
Age ≥ 75 years
2

Diabetes mellitus

Fasting glucose > 7 mmol/L or treatment with oral hypoglycaemic agent and/or insulin


1
Previous stroke, transient ischaemic attack, or thromboembolism2
Vascular disease

Previous myocardial infarction, peripheral artery disease, or aortic plaque


1
Age 65–74 years
1
Sex category (female)
1

Predicting bleeding risk

Guidelines recommend the HAS-BLED score for the prediction of bleeding risk in patients with NVAF (see Table 2).6

Using the HAS-BLED score9,11

  • Score ≥ 3 = High risk of bleeding, for which caution and regular review is recommended.

A high score identifies patients who may be at high risk of bleeding, as well as potentially modifiable bleeding risk factors. A high score does not necessarily indicate that anticoagulant medicines should be avoided.6,9


Table 2: HAS-BLED clinical score for risk of bleeding9,11
Risk factorScore
Hypertension

Systolic blood pressure > 160 mmHg


1
Abnormal kidney and/or liver function

  • Chronic dialysis, renal transplantation or serum creatinine ≥ 200 mmol/L
  • Chronic liver disease (eg, cirrhosis) or biochemical evidence of significant derangement

1 or 2
Stroke
1
Bleeding tendency or predisposition

Bleeding history or anaemia


1
Labile international normalised ratio (INR)

Time in therapeutic range < 60%


1
Elderly

Age > 65 years


1
Drugs and/or alcohol

Concomitant antiplatelets or non-steroidal anti-inflammatory drugs, or excess alcohol


1 or 2

Treat modifiable bleeding risk factors

In patients with a high bleeding risk, all bleeding risk factors should be identified and modifiable risk factors should be addressed.6,9

Based on risk factors included in the HAS-BLED score, and other bleeding risk clinical scores (HEMORR2HAGES, ATRIA, ORBIT, ABC), modifiable bleeding risk factors include:6

  • hypertension (especially when systolic blood pressure is > 160 mmHg)
  • labile INR or time in therapeutic range < 60% (in patients taking warfarin)
  • medicines that may predispose to bleeding (such as antiplatelet medicines or NSAIDs)
  • excessive alcohol consumption (typically ≥ 8 drinks/week).

Potentially modifiable bleeding risk factors include:6

  • anaemia
  • impaired kidney function
  • impaired liver function
  • reduced platelet count or function.

Non-modifiable bleeding risk factors include:6

  • age > 65 years, or ≥ 75 years
  • history of major bleeding
  • previous stroke
  • dialysis-dependent kidney disease or kidney transplant
  • cirrhotic liver disease
  • malignancy
  • genetic factors.

Overall, stroke and bleeding risk should be assessed on a patient-by-patient basis when considering an oral anticoagulant, but assessment of bleeding and other risks should continue throughout treatment.9,12-14

All patients should be educated about the benefits and risks associated with anticoagulant medicines, so they can contribute to management decisions.9

For example, some patients may accept a higher risk of bleeding, knowing that they are avoiding a stroke.9

NPS MedicineWise oral anticoagulation resources

References

  1. Aspen Pharma Pty Ltd. Warfarin (Coumadin) product information. 2017 (accessed 19 October 2017).
  2. Aspen Pharma Pty Ltd. Warfarin (Marevan) product information. 2017 (accessed 19 October 2017).
  3. Bayer Australia Ltd. Rivaroxaban (Xarelto) product information (accessed 19 October 2017).
  4. Boehringer Ingelheim Pty Limited. Dabigatran etexilate (Pradaxa) product information (accessed 19 October 2017).
  5. Bristol-Myers Squibb Australia Pty Ltd. Apixaban (Eliquis) product information (accessed 19 October 2017).
  6. Kirchhof P, Benussi S, Kotecha D, et al. 2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS: The Task Force for the management of atrial fibrillation of the European Society of Cardiology (ESC). Developed with the special contribution of the European Heart Rhythm Association (EHRA) of the ESC. Endorsed by the European Stroke Organisation (ESO). Eur Heart J 2016;37:2893-2962.
  7. National Institute for Health and Care Excellence. Clinical guideline [CG180]: Atrial fibrillation: management. London, England: National Institute for Health and Care Excellence, 2017 (accessed 19 October 2017).
  8. Cardiovascular Expert Group. Therapeutic Guidelines: Cardiovascular. West Melbourne, Victoria: Therapeutic Guidelines Ltd, 2017 (accessed 5 June 2017).
  9. Lane DA, Lip GY. Use of the CHA(2)DS(2)-VASc and HAS-BLED scores to aid decision making for thromboprophylaxis in nonvalvular atrial fibrillation. Circulation 2012;126:860-5.
  10. Pisters R, Lane DA, Nieuwlaat R, et al. A novel user-friendly score (HAS-BLED) to assess 1-year risk of major bleeding in patients with atrial fibrillation: the Euro Heart Survey. Chest 2010;138:1093-100.
  11. Bayer Australia Ltd. Rivaroxaban (Xarelto) consumer medicine information (accessed 25 October 2017).
  12. Boehringer Ingelheim Pty Limited. Dabigatran etexilate (Pradaxa) consumer medicine information (accessed 25 October 2017).
  13. Bristol-Myers Squibb Australia Pty Ltd. Apixaban (Eliquis) consumer medicine information (accessed 25 October 2017).