Introduction:

Every so often, a clinical trial comes along that changes the way we think about treatment.

In atrial fibrillation, one of those trials was called AVERROES.

And it answered a very important question: if a patient with AF can’t take warfarin, is aspirin good enough — or is there something better?

The problem before AVERROES

“We’ve known for decades that atrial fibrillation increases the risk of stroke — strokes that are often severe and disabling.
 Warfarin was the standard blood thinner, but many patients couldn’t take it — either because of bleeding risk, drug interactions, or difficulty with monitoring.
 For those patients, the fallback was often aspirin.
 But aspirin, while convenient, is much less effective at preventing stroke.”

 

The AVERROES trial design

“The AVERROES trial set out to test whether a new drug, apixaban — a direct oral anticoagulant — would be better than aspirin in patients with atrial fibrillation who were considered unsuitable for warfarin.

Over 5,500 patients were enrolled and randomised to apixaban or aspirin, then followed for strokes, systemic embolism, bleeding, and death.

The results

“The trial was stopped early — because apixaban was so much more effective.

  • It reduced the risk of stroke and systemic embolism by about 55% compared with aspirin. 
  • And crucially, it did not increase major bleeding.
     In other words, apixaban was both safer and more effective than aspirin.
  • This was a landmark moment — showing that aspirin was simply not an adequate stroke-prevention strategy in AF. 

Why it mattered:

The impact of AVERROES was huge.
 It cemented the role of direct oral anticoagulants as the preferred treatment for AF patients at risk of stroke, even in those who couldn’t take warfarin.
 And it essentially ended the era of aspirin as a serious option for stroke prevention in AF.
 Today, guidelines are clear: aspirin should not be used for this purpose — and that’s thanks in large part to AVERROES.

Closing reflection:

So what’s the lesson from AVERROES?
 That innovation, careful trial design, and the courage to test assumptions can completely reshape practice.
 For patients with atrial fibrillation, it meant fewer strokes, fewer bleeds, and better outcomes.
 And for doctors, it reminded us that we must always challenge the status quo when evidence points the way forward.

Here is a video I have done on this subject:

Aspirin or eliquis for Afib?