Treating atrial fibrillation to prevent strokes

Atrial fibrillation (AF) is the most common abnormal heart rhythm. Around 1.5 million people have been diagnosed with AF in the UK. AF happens when electrical impulses fire off in the upper chambers of the heart (the atria) in a disorganised way. These chaotic impulses cause the atria to quiver or twitch, which is known as fibrillation. People with AF have an irregular, and sometimes fast, heartbeat or pulse. They can have uncomfortable or debilitating symptoms, or sometimes no noticeable symptoms.

Revealing the danger of atrial fibrillation

Until the 1980s, AF was often regarded as harmless, because many people had the disorder without experiencing any particular symptoms. Only those who suffered unpleasant symptoms such as palpitations, sweating and difficulty in breathing would be treated.

What doctors didn’t realise until the 1980s is that AF is a major cause of strokes. Even without noticeable symptoms, AF is associated with a fivefold increase in stroke risk. This is because a blood clot can form inside the quivering atria, and if the clot travels to the brain, it can cause a stroke.

Early work by BHF Professor John Camm at St George’s University London in the 1990s showed the relative importance of heart rate and rhythm control in different patient populations, especially in people with AF. Professor Camm remains a leading international key opinion leader in the field and his work led to the development and updating of European guidelines for the management of AF. More recently, he has led clinical trials and cohort investigations into the use of oral anticoagulants in AF.

Showing the benefits of restoring a normal heart rhythm in atrial fibrillation

When people are diagnosed with AF, they are usually started on anti-clotting drugs to decrease the risk of stroke. They may also be prescribed drugs to lower their heart rate but not always to restore their normal heart rhythm. Despite these effective treatments, people with this condition still remain at an increased risk of heart and circulatory problems.

The EAST-AFNET 4 clinical trial, led by BHF Senior Clinical Research Fellow Professor Paulus Kirchhof, aimed to test whether bringing the heart rhythm back to normal soon after diagnosis in AF patients can further reduce the residual risk of heart and circulatory problems.

The results of this clinical trial were published in 2020. It showed that treatment to restore normal heart rhythm, if started soon after diagnosis of AF and with continued anti-clotting therapy, reduces complications, including strokes, without causing safety issues. Currently, it is estimated that in Europe, only one in seven patients with AF are treated with rhythm control therapy so these results have the potential to change how people with recently diagnosed AF are treated.

Discovering whether “silent” atrial fibrillation can damage the brain

Short episodes of AF are relatively common, particularly in older people, and can go unnoticed, so many people will never get diagnosed. But we don’t know if these “silent” episodes can cause damage to the brain, leading to a subsequent decline in brain function.

To find this out, we are currently funding BHF Professor Barbara Casadei and colleagues at the University of Oxford to follow 20,000 people registered in UK Biobank. They will monitor the heart rhythm of participants using a skin patch recorder and will use MRI scans to detect damage to blood vessels in the brain, alongside tests that measure people’s brain function.

If this research shows that silent AF increases the risk of stroke and dementia, then close monitoring and treatment of AF may avoid many occurrences of stroke and slow down or prevent the development of dementia. This would be a major step forward.

First published 1 June 2021