The National Institute of Health and Care Excellence (NICE) in the UK have updated the advice for patients with atrial fibrillation (AF) who take aspirin to prevent stroke. Dr Paul Jarman, Consultant Neurologist at The Physicians’ Clinic (TPC), at TPC, reviews the new guidance. “Patients with atrial fibrillation have a much higher risk of stroke, so it is important to reduce that risk as far as possible,” explains Dr Jarman.
“Although low-dose aspirin is a good preventative measure for other patients at risk of stroke, we now know that those with atrial fibrillation will be much better protected if they take an anti-coagulant medication, such as warfarin, or one of the newer anticoagulants such as dabigatran, rivaroxaban or apixaban,” he says.
What is atrial fibrillation?
In a healthy heart, the upper chambers of the heart (the atria) beat in a steady sequence with the two larger chambers (the ventricles). In atrial fibrillation, the upper chambers contract and relax very quickly, up to 400 times each minute. This disrupts signals to the ventricles, resulting in an irregular heartbeat. “It is quite common for people with atrial fibrillation to be unaware that their heart is beating abnormally.
Others experience light-headedness, dizziness and shortness of breath and notice that their pulse is prone to race,” says Dr Jarman. The condition is common, affecting around 800,000 people in the UK. Its incidence rises with age and about one in 10 people over 75 will develop it. Other cardiovascular conditions such as atherosclerosis or high blood pressure increase the risk of atrial fibrillation, but the exact cause of the problem is not well understood.
Why does atrial fibrillation increase stroke risk?
“Patients who have atrial fibrillation have an increased risk of blood clots forming in the left atrium, one of the smaller, upper chambers of the heart, and in the left atrial appendage (see the diagram top right). This is because the atrium does not contract efficiently causing blood to flow more slowly,” explains Dr Jarman.
“Stagnating blood is more liable to clot and any blood clots that form in the atrium of the heart can be carried into the brain, blocking small arteries and causing a stroke. It is therefore important to take medication to thin the blood and make it less likely to clot,” he says.
How is atrial fibrillation treated?
If you have atrial fibrillation your symptoms, if you have any, need to be reduced. “Controlling the symptoms of atrial fibrillation is important for quality of life. Medicines such as flecanide or amiodarone can help keep the heart rhythm under control, easing symptoms. In severe cases, cardiac ablation can be used to cure the problem permanently,” says Dr Jarman. You will need to take medication to reduce your stroke risk. The new NICE guidance advises doctors to use anti-coagulants rather than aspirin.
“It’s been estimated that up to 7,000 strokes per year could be prevented if every patient in the UK with atrial fibrillation was treated with anti-coagulants. Only around half are currently on this medication because, up until now, aspirin has been used as an acceptable alternative to anticoagulation by some doctors,” he notes.
Why the change in advice?
Evidence has accumulated over the last few years that anti-coagulants are better at preventing stroke in people with atrial fibrillation than low-dose aspirin. In reality, even though the advice has only recently changed, many doctors looking after patients with atrial fibrillation already prescribe anti-coagulants. “Anticoagulant medication does carry risks, principally the risk of internal bleeding, including bleeds into the brain.
However, this small risk is far outweighed by the benefits,” explains Dr Jarman The newer anticoagulants dabigatran, rivaroxaban or apixaban do not require monitoring, unlike warfarin, and are thought to be associated with a lower risk of serious bleeding. They are also less likely to interact with other medications.
Not everyone with atrial fibrillation needs to take anticoagulants
“Around 6% of patients with atrial fibrillation are under 65 and do not have conditions such as high blood pressure, diabetes or previous stroke. These patients are considered to be at lower risk of stroke from atrial fibrillation and may not need anti-coagulants,” stresses Dr Jarman Are there any alternatives to anticoagulants? Left atrial appendage occlusion devices are becoming available.
The invasive cardiac procedure required to deploy them does carry a small risk, but they provide a long-term solution. “These devices are relatively new and available in only a few specialised centres at present, but they can prevent stroke in people with atrial fibrillation without the need for anticoagulation,” reports Dr Jarman.