(a) In patients with atrial fibrillation, 2 tools are best for predicting risk for stroke; a third tool is best for predicting risk for bleeding

Lopes RD, Crowley MJ, Shah BR, et al. Stroke Prevention in Atrial Fibrillation AHRQ Comparative Effectiveness Review. Rockville, MD: Agency for Healthcare Research and Quality; 2013 Aug. Report No 13-EHC113-EF.

Review question

How effective are tools for predicting stroke and bleeding risk in patients with atrial fibrillation?

Background

Atrial fibrillation is an abnormal heart rhythm that can cause small clots to form in the heart. These clots can travel to the brain, causing a stroke.

Anticoagulant (or blood thinning) treatment is the therapy of choice for preventing stroke in non-valvular atrial fibrillation. However, anticoagulants can cause bleeding. People with atrial fibrillation vary a lot in their risk of stroke from AF, and in their risk of bleeding.

Prediction tools assess which people are most likely to benefit from treatment and which are most likely to be harmed.

How the review was done

This summary is based on a systematic review of 37 studies on predicting stroke risk and 17 studies on predicting bleeding in people with atrial fibrillation. Average age of participants ranged from 53 to 81 years. Publication period was 2000 to 2012.

What the researchers found

Scores from the CHADS2 and CHA2DS2-VASc are best for predicting risk for stroke. Their average prediction value is 0.70 (ranging from 0.66 to 0.75).

A value of 0.50 means that the tool is no better than chance in predicting an outcome. A value of 1.0 means that the tool predicts an event with certainty.

The strength of the evidence for these 2 tools is low.

The HAS-BLED score is best for predicting bleeding risk. Strength of the evidence is moderate.

Conclusions

The CHADS2 and CHA2DS2-VASc scores are best for predicting stroke in people with atrial fibrillation.

HAS-BLED scores are best for predicting bleeding risk.

Tools for predicting stroke or bleeding

(b) In patients with atrial fibrillation, dabigatran, and apixaban are better than warfarin for preventing stroke; results differ on risk for bleeding

Lopes RD, Crowley MJ, Shah BR, et al. Stroke Prevention in Atrial Fibrillation AHRQ Comparative Effectiveness Review. Rockville, MD: Agency for Healthcare Research and Quality; 2013 Aug. Report No 13-EHC113-EF.

Review question

How effective are newer treatments for stroke and bleeding in patients with atrial fibrillation?

Background

Atrial fibrillation (AF) is an abnormal heart rhythm that can cause small clots to form in the heart. These clots can travel to the brain (causing a stroke) or to other organs (systemic embolism—for example, causing a heart attack).

Anticoagulant (or blood thinning) treatment is the therapy of choice for preventing stroke in non-valvular atrial fibrillation. However, anticoagulants can cause abnormal bleeding (for example, in the bowel or brain). New treatments for stroke prevention exist.

How the review was done

This summary is based on a systematic review of 43 studies of interventions for preventing stroke and 13 studies of anticoagulation strategies for patients having invasive procedures. Average age of participants ranged from 53 to 81 years. Publication period was 2000 to 2012.

Drugs evaluated included apixaban, aspirin, clopidogrel, dabigatran, edoxaban, rivaroxaban, and warfarin.

What the researchers found

Dabigatran, 150 mg, was better than warfarin in preventing stroke (including bleeding into the brain) and systemic embolism by 34% (1.1% /year vs 1.7%/year).

Rivaroxaban was no worse than warfarin in preventing stroke or systemic embolism. Rates of major bleeding and death were similar.

Apixaban was better than warfarin in preventing stroke and systemic embolism by 21% (1.3%/year vs 1.6%/year).

Apixaban was better than warfarin in preventing major bleeding by 31%t and death by 21%.

Apixaban was also better than aspirin in reducing stroke or systemic embolism by 55% (1.6%/year vs 3.7%/year). Rates of bleeding (including major bleeding in patients not suitable for oral anti-coagulation) were similar.

No studies directly compared the newer therapies.

Conclusion

In patients with atrial fibrillation, dabigatran and apixaban are better than warfarin in preventing stroke.

Apixaban is also better than warfarin in preventing bleeding and death.