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Clinical Articles, News & Views

Apixaban strengthens its case in AF

Apixaban is superior to warfarin as a first line treatment for people with atrial fibrillation (AF), regardless of baseline risk for either stroke or bleeding, according to a new analysis1 of data from the Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation (ARISTOTLE) trial. The authors found no statistical interaction between the benefits of apixaban and baseline risks, measured using validated scores CHADS2, CHA2DS2VASc, and HAS-BLED.

The authors assessed how the results of ARISTOTLE participants differed according to patients’ CHADS2, CHA2DS2VASc, and HAS-BLED scores. They calculated CHADS2, CHA2DS2VASc, and HAS-BLED scores of patients at their randomisation to apixaban or warfarin. Efficacy analyses were by intention to treat, and safety analyses were of the population who received the study drug.

Apixaban significantly reduced stroke or systemic embolism with no evidence of a differential effect by risk of stroke (CHADS2 1, 2, or ≥3, p for interaction=0·4457; or CHA2DS2VASc 1, 2, or ≥3, p for interaction=0·1210) or bleeding (HAS-BLED 0—1, 2, or ≥3, p for interaction=0·9422). Patients who received apixaban had lower rates of major bleeding than did those who received warfarin, with no difference across all score categories (CHADS2, p for interaction=0·4018; CHA2DS2VASc, p for interaction=0·2059; HAS-BLED, p for interaction=0·7127).

The relative risk reduction in intracranial bleeding tended to be greater in patients with HAS-BLED scores of 3 or higher than in those with HAS-BLED scores of 0–1.

These findings should not be the final word, according to an accompanying editorial.2 Tests of statistical interaction are a blunt instrument, say the authors, particularly in secondary analyses that may be underpowered. On current evidence, we would need to treat 100 adults with apixaban instead of warfarin for a year to prevent one more thromboembolic event, one more bleed, or one more death, they say. The number needed to treat (NNT) varies with baseline risk of stroke, from roughly 120 for those at lowest risk to roughly 60 for those at highest risk. Cost effectiveness will probably vary also, so risk stratification remains an important tool for now, they conclude.

References

1. Lopes RD, Al-Khatib SM, Wallentin L, et al. Efficacy and safety of apixaban compared with warfarin according to patient risk of stroke and of bleeding in atrial fibrillation: a secondary analysis of a randomised controlled trial. The Lancet 2012.  http://dx.doi.org/10.1016/S0140-6736(12)60986-6/

2. Vassiliou VS, Flynn PD. Apixaban in atrial fibrillation: does predicted risk matter? The Lancet 2012. http://dx.doi.org/10.1016/S0140-6736(12)61673-0/

Published on: November 15, 2012

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ENDORSED BY

  • ArrhythmiaAlliance
  • Stars
  • Anticoagulation Europe
  • Atrial Fibrillation Association
 

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