Atrial fibrillation, stroke risk and blood-thinning medication

People with atrial fibrillation (AF) are at increased risk of stroke. The likelihood of stroke increases 5 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.

Dr Tim Holt explains how having AF can increase a person’s risk of stroke.

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The consequences of having a stroke can be devastating. (For more see our website on Stroke).

James did not know he had AF until he had a stroke, aged 59. He described his memories of the stroke and its impact on his life.

Age at interview 63

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Age at diagnosis 59

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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.”

Keith had a TIA/minor stroke after driving back from Bath. His speech was slurred and he felt detached from his surroundings.

Age at interview 61

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Age at diagnosis 57

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George X experienced two TIAs/minor strokes; the first 8 years ago, the second 4 years ago. He described the symptoms of his first TIA.

Age at interview 78

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Age at diagnosis 63

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Maggie found it very, very frightening’ being on her own when she experienced a lot of dizziness, minor seizures and a lack of feeling on one side shortly after her second ablation.

Age at interview 70

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Age at diagnosis 61

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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.

James’ wife Jenny said that they had never heard of AF before her husband’s stroke. She feels that they now have to live with thoughts of what if.

Age at interview 55

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Chris Y had symptoms of paroxysmal AF for ten years, but it was only after his TIA/minor stroke that AF was caught on an ECG and diagnosed.

Age at interview 64

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Age at diagnosis 62

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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.

Aware of her increased risk of stroke, Ginny decided to have an ablation to keep her heart in check.

Age at interview 49

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Age at diagnosis 45

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Marianne fears she will have a stroke in the future, although this may not happen. She fears being permanently disabled.

Age at interview 72

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Age at diagnosis 54

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(*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).

Dr Tim Holt explains how anticoagulants can help reduce the risk of stroke and suggests reasons why people might be reluctant to take them.

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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.

After his TIA, Keith reluctantly accepted the need for warfarin rather than aspirin.

Age at interview 61

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Age at diagnosis 57

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Brendan has had little difficulty adjusting to warfarin. He explained the purpose of anticoagulants.

Age at interview 59

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Age at diagnosis 57

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Dot was both relieved and worried when it was explained that her stroke risk was constant, whether she had occasional or persistent episodes.

Age at interview 64

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Age at diagnosis 55

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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”.

Mary, who was reluctantly taking warfarin, wondered whether her risk of stroke warranted taking medication.

Age at interview 84

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Age at diagnosis 84

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Elisabeth Y explained why she refuses to take warfarin.

Age at interview 69

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Age at diagnosis 63

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At times the decision to go off warfarin was made after successful surgery to treat AF. This depended, however, on individual attitudes to risk.

Following a successful ablation procedure, Chris X decided not to carry on taking warfarin.

Age at interview 65

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Age at diagnosis 50

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Bob decided to continue taking warfarin despite a successful ablation.

Age at interview 66

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Age at diagnosis 59

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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.

Paul stopped taking warfarin after 9 months. His doctor told him he did not fit into the higher risk bracket for stroke.

Age at interview 57

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Age at diagnosis 55

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A consultant Bob met at a conference told him that some GPs are afraid to prescribe warfarin because of the risk of internal bleeding. Bob believes you have to make up your own mind.

Age at interview 66

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Age at diagnosis 59

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Carin spoke of contradictory messages which influenced her decision not to take warfarin.

Age at interview 62

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Age at diagnosis 55

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(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.

Maggie assumed aspirin was safe until she had a gastrointestinal bleed. She no longer takes any form of blood thinning medication.

Age at interview 70

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Age at diagnosis 61

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Roger’s cardiologist took him off warfarin and put him on aspirin which had fewer side effects. However, after having a TIA/minor stroke, Roger was put back on warfarin.

Age at interview 60

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Age at diagnosis 50

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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).

Dr Tim Holt explains why aspirin is no longer considered effective in reducing stroke risk in people with atrial fibrillation.

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