Atrial fibrillation

Atrial fibrillation, stroke risk and blood thinning medication

People with atrial fibrillation (AF) are at increased risk of stroke. The likelihood of stroke increases five times among those with AF, with 12,500 strokes directly attributable to AF occurring annually (National Institute for Health and Care Excellence June 2014). Here we look at the increased risk of stroke for people with atrial fibrillation (AF), explore people’s experiences of stroke and Transient Ischaemic Attack (TIA or minor stroke) and consider how anticoagulants (blood thinning medications) such as warfarin can reduce the possibility of having a stroke. We also explain why aspirin is no longer recommended as a blood thinner for people with AF.
 
Atrial fibrillation and stroke risk
We asked Dr Tim Holt, an academic GP to talk about the increased risk of stroke for people with AF.
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Read below
The consequences of having a stroke can be devastating. (For more see our website on Stroke).
We also spoke with a number of people who had experienced a Transient Ischaemic Attack (TIA or minor stroke) caused by a temporary lack of blood to part of the brain. (For more see our website on TIA and minor stroke). They described symptoms similar to stroke, including dizziness, numbness, slurred speech and detachment. Chris Y noticed his arm was ‘getting a bit numb’ and his speech was ‘gobbledy gook’ for 10-15 seconds after coming back from jogging. Unlike a full stroke, TIA/minor stroke episodes are usually resolved after a short time. They can however, increase the risk of possible further TIAs or a full stroke. As George X was told by a paramedic when he had a TIA, “Let that be a warning to you, old fellow. It’s a precursor to a main stroke.”
An early diagnosis of AF and appropriate treatment may reduce the risk of stroke and TIA/minor stroke. People spoke of missed opportunities for diagnosis which, in retrospect, they felt could have minimised the risk.
People we interviewed were aware of the increased risk of stroke as a result of having AF, and some people worried about this. Paul, who was asymptomatic (had no symptoms of AF), said that having a stroke was his ‘biggest fear’, while George Y was keen to avoid anything that might bring on a stroke which he regarded as ‘the most debilitating, sudden, life changing disabilities that anyone could be given’. Ginny, who had worked with elderly people who had had a stroke, said ‘You don’t want a stroke, I can tell you that.’ George X, who has had two TIAs (minor strokes), worried about having a major stroke. He said: ‘I tell you now I’d end it there and then. I’d finish it.’ Some said that they would have had their symptoms investigated sooner if they had realised they were at increased risk of stroke.
(*For more on ablation see ‘Medical procedures and interventions for atrial fibrillation’)

Stroke risk and blood thinning medication (anticoagulants)
Desire to avoid a stroke is an important focus for people with AF. Anticoagulants (medicines which thin the blood) can be effective in stroke prevention and are recommended as a treatment for AF for those people with a moderate-high risk of stroke. Anticoagulants include warfarin and the newer medications dabigatran, rivaroxaban, and apixaban. (For more see ‘Alternatives to warfarin for atrial fibrillation: the new anticoagulants'). Yet despite the benefits of taking anticoagulants to reduce stroke risk, only 45% of those who are eligible for these treatments currently receive them (National Institute for Health and Care Excellence June 2014).
Among the people we spoke to, decisions about whether or not to take anticoagulants were often closely linked to attitudes to stroke risk. Some were positive about their need for treatment. Pauline said that she would be too afraid to stop taking the medication that her cardiologist had prescribed, while Jo did not mind being on warfarin because it was ‘keeping me alive and preventing a stroke’. David Y trusted his consultant and took his advice to start on warfarin. Eileen, whose mother and aunt had had strokes, was ‘only too pleased’ to be on warfarin to reduce her stroke risk.
Others, however, were unsure whether warfarin was appropriate for them, or, after considering their circumstances, decided not to take it. George X found that taking warfarin made him go ‘as red as a beetroot’ and his doctors took him straight off it. Martin felt that stroke risk was assessed and anticoagulants prescribed without attention to individual circumstances or preferences. He called this ‘medicine by numerology.’
At times the decision to go off warfarin was made after successful surgery to treat AF. This depended, however, on individual attitudes to risk.
Some people reported being confused by the advice given by health professionals. They felt they were sometimes given contradictory messages leaving them unsure whether to take warfarin or not.
(For more see ‘What is it like being on warfarin for atrial fibrillation?’)

Aspirin as a blood thinning medication? Current advice
When we interviewed people in 2012 aspirin was still considered a useful treatment to protect people with atrial fibrillation (AF) from strokes by thinning the blood. Some people we spoke to preferred taking aspirin to warfarin. For them aspirin was believed to be a simple alternative that needed no monitoring and promised fewer side effects. Yet while aspirin was widely used, some people expressed concern. Aspirin was not risk-free and could increase the risk of bleeding. Elisabeth Y experienced nose bleeds and bleeding after dental surgery. Some doubted whether aspirin was effective enough to prevent strokes. Noel spoke to doctors at an AF conference who were surprised that he was taking aspirin rather than warfarin. They told him that ‘aspirin has little or no effect on people with AF’, which, at the time, contradicted his consultant’s advice to ‘stay on aspirin’. Eileen preferred warfarin as an anticoagulant, believing that while aspirin was ‘good for heart attack victims’ it was not a sufficient anticoagulant for AF patients.
Since the interviews, new guidelines on AF have been published by the National Institute for Health and Care Excellence (NICE) (CG180 June 2014). The guidelines state that doctors should not offer aspirin as a single drug for stroke prevention to people with atrial fibrillation. Evidence suggests that warfarin and the newer anticoagulants such as dabigatran, rivaroxaban or apixaban are much more effective than aspirin at preventing strokes. (For more see ‘Alternatives to warfarin for atrial fibrillation: the new anticoagulants’).

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