Rationale and impact

These sections briefly explain why the committee made the recommendations and how they might affect practice.

Detection and diagnosis

Recommendations 1.1.2 and 1.1.3

Why the committee made the recommendations

The evidence did not support changing the recommended diagnostic tests to either replace 12‑lead ECG as the test to confirm persistent atrial fibrillation or replace pulse palpation as the initial step for persistent atrial fibrillation in a 2‑step strategy. The committee clarified that 12‑lead ECG should be used as the test to confirm atrial fibrillation, to prevent the use of less accurate ECG devices, such as mobile and lead‑I ECG devices. The committee agreed that, although the evidence showed that accuracy varied, there was some evidence that new devices were accurate and showed promise. It was noted that NICE has produced diagnostics guidance on lead-I ECG devices for detecting symptomatic atrial fibrillation using single time point testing in primary care. The committee made a research recommendation on tests to diagnose persistent atrial fibrillation to encourage further high‑quality research in this area to guide future practice.

The committee agreed that the evidence on tests to detect paroxysmal atrial fibrillation was not clear enough to warrant a change in practice from the 2014 recommendation. However, the evidence did show that longer durations of detection increased accuracy. The committee made a research recommendation on tests to diagnose paroxysmal atrial fibrillation.

How the recommendations might affect practice

The recommendations reflect current good practice and are unlikely to have an impact on practice.

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Stroke risk

Recommendation 1.2.1

Why the committee made the recommendations

The committee decided to prioritise identifying people above or below a certain risk threshold (discrimination) in its interpretation of the evidence rather than estimating a person's risk of stroke in absolute terms.

The evidence suggested that a score of 2 or more is the ideal threshold for the CHA2DS2‑VASC in terms of indicating the need for anticoagulation. (Men with a CHA2DS2‑VASc score of 1 were regarded as being at intermediate risk, and a group in whom anticoagulation should also be considered.) The evidence showed that this threshold of 2 or more offered a good combination of high sensitivity (0.92) and adequate specificity (0.23).

The high sensitivity means that the tool would correctly identify almost everyone who would later have a stroke if they did not receive anticoagulants. Importantly, this will allow them to be prescribed anticoagulants to reduce their risk of stroke.

The adequate specificity means that 23% of the people who would not later have a stroke (even when not taking anticoagulants) would be correctly identified as not needing anticoagulation. This would prevent these people from having adverse events from anticoagulants. It also means that 77% of people who would not later have a stroke (without anticoagulation) would be wrongly identified as needing anticoagulation. However, this was thought to be acceptable given the perceived lesser harms from unnecessarily giving anticoagulants compared with not giving anticoagulants to people who need them, together with the inevitable trade‑off between sensitivity and specificity.

The ATRIA stroke risk score was shown to have better overall accuracy, but although it had better specificity than CHA2DS2‑VASc (fewer false-positive results) it had lower sensitivity, meaning that more people at risk would be missed (more false‑negative results) compared with the CHA2DS2‑VASc score. As already suggested, sensitivity was agreed by the committee to be more important than specificity because the risks of unnecessary anticoagulation are outweighed by the risks of not treating people who need anticoagulation. In addition, the ATRIA risk score may result in a time delay in calculating the results.

The committee also discussed that the evidence for the QStroke risk calculator suggested that it might be a useful tool. However, the evidence was limited, and they agreed that further research was needed.

How the recommendation might affect practice

The recommendation does not constitute a change in practice, and so there would not be a resource impact on the NHS.

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Bleeding risk

Recommendations 1.2.2 to 1.2.4

Why the committee made the recommendations

The committee agreed that anticoagulation should usually be considered in people at risk of stroke even if bleeding risk is high, and so a bleeding risk tool should not be used to provide a cut off for determining who should have anticoagulation. Instead, the tool should be used to provide accurate knowledge of absolute bleeding risk, which can support discussions between the person and their healthcare professional about bleeding risk modification and appropriate levels of vigilance. They therefore agreed that accurately estimating absolute risk (calibration) is more important than identifying a risk threshold for anticoagulation (discrimination) when choosing between different bleeding risk tools.

The committee focused on calibration data for the tools with the most evidence: ORBIT, HAS-BLED and ATRIA. The calibration evidence clearly suggested that ORBIT was more accurate than HAS‑BLED and ATRIA at predicting absolute risk of major bleeding, both for people using vitamin K antagonists and those using direct‑acting oral anticoagulants. Importantly, ORBIT was better calibrated at all levels of major bleeding risk, including higher levels. ORBIT was also better at predicting absolute risk of intracranial haemorrhage.

The discrimination data showed little difference between tools in predicting major bleeding, with some outcome measures showing no difference and others showing a slight benefit for either ORBIT or HAS‑BLED. Evidence showed that ORBIT had a significantly higher specificity and a slighter lower sensitivity than the other tools, but the committee agreed that the lower sensitivity would not be a drawback when used to inform discussions of risk.

The committee agreed that the evidence overall, and particularly the calibration data demonstrating higher accuracy of absolute risk, strongly supported ORBIT as the tool of choice.

The committee agreed that NICE's previous advice on monitoring and addressing modifiable risk factors was still relevant and added reversible causes of anaemia because it is a component of the ORBIT tool.

How the recommendations might affect practice

Use of the ORBIT score is a change in practice, which will take time to implement. The committee considered that the more accurate prediction of the absolute risk of bleeding is a real advantage in supporting patients and clinicians in shared decision making, which should lead to better clinical outcomes. The committee considered carefully a number of practical issues set out in this section. Overall, the committee concluded that this change is one that is worth making.

One potential concern discussed by the committee is that ORBIT does not include all of the modifiable risk factors included in HAS‑BLED so does not serve as a reminder of these to clinicians. However, the committee considered that fully investigating modifiable risk factors is established clinical practice, regardless of the tool used.

Another potential challenge is that ORBIT is not the recommended bleeding risk tool for other conditions (such as venous thromboembolism). Therefore, an initial transition period may be needed for training and education in both primary and secondary care while healthcare professionals become familiar with the tool. This will have a resource impact, although it will be time limited. The committee also noted that use of the ORBIT tool, and access to online versions, is straightforward.

Finally, the committee also discussed that, unlike HAS‑BLED, ORBIT is not embedded in GP systems, which may cause some initial practical difficulties. However, because this will involve changes to centralised software, it is thought that it will be straightforward to implement and ORBIT will quickly be included in GP systems. Neither tool is included in hospital systems although both are widely available on smartphone apps.

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Stroke prevention

Recommendations 1.6.1 to 1.6.8

Why the committee made the recommendations

Evidence from an analysis of several studies showed that direct‑acting oral anticoagulants are more effective than warfarin for a number of outcomes. An economic model also showed that they offered a better balance of benefits to costs than warfarin. There were no studies directly comparing the direct‑acting anticoagulants head‑to‑head but indirect comparisons based on the clinical evidence showed that the different direct‑acting oral anticoagulants offered different benefits depending on the outcome considered. When all these outcomes were combined in the cost‑effectiveness analysis, apixaban was the most clinically effective and cost‑effective anticoagulant based on UK drug tariff prices at the time. However, the committee had concerns over the lack of head‑to‑head comparisons, differences in the study populations and uncertainties in the economic model.

Based on the evidence and their experience, the committee decided not to recommend one direct‑acting oral anticoagulant over the others, but instead to emphasise that treatment should be tailored to the person's clinical needs and preferences. Each anticoagulant has different risks and benefits that should be considered and fully discussed with the person as part of informed shared decision making. The committee highlighted that the choice might be affected by factors such as renal impairment and swallowing difficulties, and that healthcare professionals should refer to the BNF for advice on contraindications and cautions. They also stressed the importance of adherence and factors that might affect this, such as dosing frequency, when making the decision. If direct‑acting oral anticoagulants are not suitable, for example in people with antiphospholipid syndrome, the committee agreed that a vitamin K antagonist should be offered.

For people already established and stable on a vitamin K antagonist, the committee agreed that the benefits of changing to a direct‑acting anticoagulant need to be discussed. Therefore, the risks and benefits of changing medication, the person's time in therapeutic range and the person's preferences should be explored at their next routine appointment.

The committee agreed that the existing thresholds for the CHA2DS2‑VASc score threshold for anticoagulation are in line with current practice.

Although bleeding risk scores may occasionally be used as a reason not to offer anticoagulation, the committee agreed that they should typically be used as a prompt to identify and manage modifiable risk factors for bleeding rather than as a reason for not offering anticoagulation in people at increased risk. The committee discussed that when anticoagulation is not given because of bleeding risk, people should have regular review and reconsideration for treatment.

The committee were concerned that anticoagulation is sometimes not recommended for people at risk of falls and for older people, even though age is factored into the bleeding risk score and falls are rarely a cause of major haemorrhage. Age was therefore added to the previous recommendation on people at risk of falls to ensure that anticoagulation is offered in this population when needed. The benefits and harms should be discussed with the person.

How the recommendations might affect practice

The recommendations are likely to lead to a change in current practice, with a reduction in warfarin use. The committee noted that this has been a prescribing trend over recent years and it may lead to a contraction in warfarin clinic services. The unit cost of direct‑acting anticoagulants is greater than that for warfarin, so there is likely to be a resource impact from increased use of direct‑acting anticoagulants.

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Rate control

Recommendations 1.7.2 to 1.7.6

Why the committee made the recommendations

The committee made some updates to the 2014 recommendations, based on their experience and knowledge.

The use of beta‑blockers or rate‑limiting calcium‑channel blockers for initial rate‑control treatment was retained by the committee because this is current practice and there was insufficient evidence to suggest an alternative option. The committee agreed that the choice of treatment should still be made based on the symptoms, heart rate, comorbidities and preferences of those being treated.

The committee agreed that the recommendations should refer to NICE's guideline on chronic heart failure for advice on using beta‑blockers and avoiding rate‑limiting calcium‑channel blockers such as diltiazem and verapamil in people who have atrial fibrillation with heart failure.

The committee agreed that digoxin monotherapy for non-paroxysmal atrial fibrillation should continue to be considered for people who are sedentary. Based on their experience, the committee agreed that it may also be considered as a treatment option when other rate‑limiting drugs are not suitable, so they expanded the recommendation in the previous guideline to also cover these circumstances. The committee were aware that some clinicians feel that digoxin monotherapy is often better than alternatives for improving symptoms; however, the lack of evidence currently available meant that the recommendation for digoxin was not expanded to cover further groups of people.

In the absence of new evidence, the committee also agreed with the existing recommendation for combination therapy options if initial monotherapy fails, which is consistent with the committee's experience and current practice.

There was a lack of evidence on long‑term rate control, and the committee were aware of numerous serious side effects associated with the long‑term use of amiodarone (including thyroid, lung and nerve damage), many of which are irreversible. The committee noted that although the most common side effects were less severe, the occurrence of severe side effects was unpredictable and long‑term rate control with amiodarone should be avoided. Amiodarone should only be used as an interim therapy, for example while waiting for cardioversion, and would not usually be taken for longer than 12 months.

How the recommendations might affect practice

The recommendations reflect current practice. Digoxin monotherapy may now be an option in non‑paroxysmal atrial fibrillation if comorbidities or patient preferences limit other rate‑control drug choices. However, the committee agreed that this already happens in practice.

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Left atrial ablation

Recommendations 1.7.19 to 1.7.20

Why the committee made the recommendations

Ablation may be a treatment option if antiarrhythmic drug treatment has not been successful or is not tolerated. The committee reviewed new clinical and health economic evidence for the different types of ablation for people with paroxysmal atrial fibrillation and agreed that the catheter ablation techniques were the most clinically effective ablation options. Thoracoscopy and the hybrid techniques led to lower recurrence, but they also led to more serious adverse effects. There were no clear differences in efficacy between the 4 catheter ablation techniques: radiofrequency point‑by‑point, radiofrequency multi‑electrode, laser and cryoballoon ablation.

A new economic model was developed for the guideline using the clinical evidence from people with paroxysmal atrial fibrillation. It showed that radiofrequency point‑by‑point ablation was more cost effective over a lifetime than antiarrhythmic drug treatment and other ablation strategies in people for whom 1 or more antiarrhythmic drug has failed. Cryoballoon, radiofrequency multi-electrode and laser ablation were the second, third and fourth most cost‑effective options respectively.

The committee acknowledged that the NHS reference cost used for the catheter ablation procedures may not fully capture differences in resource use between the different techniques. However, despite further analysis to adjust costs and account for this, radiofrequency point‑by‑point ablation remained the most cost‑effective option, and other catheter ablation techniques are therefore unlikely to provide a cost‑effective use of NHS resources. Based on the economic model results the committee agreed that radiofrequency point‑by‑point ablation should be considered in people with symptomatic paroxysmal atrial fibrillation if drug treatment is unsuccessful, unsuitable or not tolerated.

The committee noted that cryoballoon and laser ablation may be more suitable for some patients because they can sometimes be carried out without general anaesthesia, and cryoballoon ablation may be quicker to perform, with same‑day discharge more likely. There is also an increased risk of fluid overload from saline irrigated radiofrequency ablation. They decided that either cryoballoon or laser ablation could be considered if radiofrequency point‑by‑point ablation is not suitable; for example, if a short procedure time is a priority or for people with a recent history of decompensated heart failure who are at increased risk of fluid overload. Radiofrequency multi-electrode was not included as an alternative due to its lower efficacy relative to cryoballoon and laser ablation and concerns about a higher risk of stroke.

There was limited evidence for ablation in people with persistent atrial fibrillation. Despite this, the committee decided that the evidence, combined with their experience and knowledge (also noting the Packer et al. CABANA randomized clinical trial, 2019, which contained a mixed population of people with persistent and paroxysmal atrial fibrillation) was sufficient to support ablation as an option to be considered for those with persistent symptoms that are not alleviated by, or who cannot have, antiarrhythmic drugs. The committee agreed that ablation can be effective in people with persistent atrial fibrillation, and that this population might have as much to gain from ablation as people with paroxysmal symptoms. The committee agreed that the cost‑effectiveness analyses of different types of ablation in paroxysmal atrial fibrillation could also be applied to this population.

The committee emphasised the importance of discussing the risks and benefits of catheter ablation with the person, in particular the risk of adverse events. The discussion should also include that, in the experience of the committee, the effects of ablation may not be long term.

How the recommendations might affect practice

The committee noted that the recommendations are likely to reinforce current practice. Ablation is carried out in a relatively restricted population (approximately 1% to 2% of all people with atrial fibrillation currently have ablation) and is usually reserved for people in whom antiarrhythmic drugs have failed. The recommendation is likely to lead to a change in the types of ablation offered, with more people receiving radiofrequency point‑by‑point ablation and fewer having other catheter ablation techniques.

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Preventing recurrence after ablation

Recommendations 1.7.22 and 1.7.23

Why the committee made the recommendations

Most of the evidence on preventing recurrence after ablation was for amiodarone. The evidence suggested that amiodarone may reduce recurrence of atrial fibrillation after ablation. However, there was evidence of an increased risk of hospitalisation and the committee noted the known side effects of amiodarone, which, although rare, can be severe and life‑threatening.

There was a lack of evidence for other antiarrhythmic drugs and there were no comparisons between different antiarrhythmic drugs. Therefore, the committee agreed that there was too much uncertainty to recommend one specific antiarrhythmic drug over others.

In addition, the studies often made no distinction between people who had been on antiarrhythmic drugs up to ablation and those who had not. There is variation in current practice on whether people who were not previously taking antiarrhythmic drugs should start them after ablation to reduce recurrence. However, the evidence did not support making separate recommendations to clarify this.

The committee decided that antiarrhythmic drug treatment should be considered after ablation, but only after discussion with the person, taking into account their preferences for treatment and the potential individual risks and benefits. In particular, the committee noted that people should fully understand the potential adverse events associated with these drugs. While there is some variation, the committee agreed that good current practice is for patients taking antiarrhythmic drugs up to ablation to continue them for 3 months after ablation and reassess the need for drug treatment after this time.

How the recommendations might affect practice

There is some variation in current practice. Practice is likely to change in some centres both in prescribing and in the need for a more formal reassessment of treatment at 3 months. The impact on use of antiarrhythmic drugs is difficult to predict, but there may be an increase from current levels. Increased resources may be needed for reassessment, but it is anticipated that this could be performed at routine follow‑up appointments with a cardiologist.

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Rate and rhythm control for people presenting acutely

Recommendation 1.8.3

Why the committee made the recommendation

The committee agreed that the evidence was too limited in quality and quantity to be able to specify a preferred rate‑control drug for acute atrial fibrillation. Although there was some evidence that amiodarone was better than digoxin for rate control, the committee had concerns about the quality of the evidence and the short timeframe used in 1 study, which it agreed could disadvantage digoxin. In addition, there was limited evidence available for morbidity and adverse events for this comparison and no evidence identified for other drug classes.

The committee highlighted that the existing recommendations gave no guidance on acute atrial fibrillation with acute decompensated heart failure. Using their expertise and experience the committee agreed that advice on the use of beta-blockers and rate-limiting calcium‑channel blockers should be included because they can lead to further deterioration in people with pulmonary oedema caused by heart failure.

How the recommendation might affect practice

The recommendations do not constitute a change in practice, and so are unlikely to have a resource impact.

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Preventing postoperative atrial fibrillation

Recommendations 1.10.3 and 1.10.4

Why the committee made the recommendations

The committee noted that the most recent studies reviewed showed no benefit from statins in reducing atrial fibrillation after cardiothoracic surgery. This contrasted with analysis of the evidence overall, which showed a small but definite benefit from statins. The committee agreed that the evidence of no effect in the newer studies was important, because these studies were larger and of higher quality than the older studies included in the analysis.

Although the newer studies suggested that statins did not affect the short‑term risk of stroke, they did suggest a greater risk of mortality in the peri‑operative period compared with placebo treatment or usual care. The committee agreed that although the additional risk of death was probably small, it was important, especially alongside the lack of convincing evidence of benefit.

For these reasons, the committee decided that statins should not be given to prevent atrial fibrillation after cardiothoracic surgery. However, the committee wanted to highlight that statins have an important role in preventing cardiovascular events other than atrial fibrillation and that people already taking statins for other reasons should continue to do so.

How the recommendations might affect practice

The committee agreed that the recommendation would not constitute a change in practice, and that there would not be a resource impact on the NHS.

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Managing atrial fibrillation after cardiothoracic surgery

Recommendations 1.10.5 and 1.10.6

Why the committee made the recommendations

The evidence on managing postoperative atrial fibrillation after cardiothoracic surgery in people without pre‑existing atrial fibrillation was limited – many of the studies reviewed were old and included small numbers of participants. There were few studies comparing drug classes, and the committee agreed that they could not recommend a particular class of drugs based on such limited evidence.

One larger study comparing mixed rate control and rhythm control with a potassium‑channel blocker (amiodarone) with or without rate control suggested little difference between the 2 groups. Based on this evidence and their experience, the committee decided that rhythm control could be considered but that the evidence no longer supported the stronger recommendation included in the 2014 guideline. The committee noted that postoperative atrial fibrillation often resolves naturally, meaning that rate control rather than rhythm control may be a suitable option for some people. Reducing the emphasis on rhythm‑control strategies will allow rate‑control strategies to be considered if appropriate for the person.

The committee were also aware of the risk of adverse events if amiodarone, a rhythm control drug, is taken long‑term. They highlighted that if a rhythm‑control strategy is chosen, the need for rhythm control drugs should be reassessed at approximately 6 weeks, in line with current practice, and they should not be continued automatically for long periods of time. The committee agreed that 6 weeks is an appropriate time point to assess the person's recovery, including for example prosthetic valve function, and to check if sinus rhythm has been restored.

The committee did not make a separate recommendation for people with pre‑existing atrial fibrillation because of a lack of evidence. The committee noted that most people undergoing mitral valve surgery with pre‑existing atrial fibrillation would undergo left atrial surgery to treat atrial fibrillation at the same time.

How the recommendations might affect practice

Rhythm control for the treatment of new‑onset atrial fibrillation after cardiothoracic surgery is current practice and amiodarone is most commonly used. This can still be considered, but there may be a reduction in the use of rhythm control in this population and an increase in the use of rate‑control drugs instead.

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Stopping anticoagulation

Recommendations 1.11.1 and 1.11.2

Why the committee made the recommendations

There was limited evidence on whether to continue anticoagulation or to stop it and switch to aspirin after successful treatment of atrial fibrillation by catheter ablation. The committee agreed that the evidence was insufficient and that there was too much uncertainty in the results to make a recommendation based on the evidence. The committee therefore developed research recommendations on stopping anticoagulation after ablation and stopping anticoagulation after resolution of postoperative atrial fibrillation to encourage further research.

The committee was concerned about the potential withdrawal of anticoagulation in people who had not had ablation or cardiac surgery for atrial fibrillation, but in whom sinus rhythm is now present and atrial fibrillation is no longer detectable. In particular, the committee noted that paroxysmal atrial fibrillation is not always detectable. Based on their experience, the committee made a consensus‑based recommendation to ensure that decisions about stopping anticoagulation in this population are based on formal risk assessment of stroke and bleeding risks and patient preference.

How the recommendations might affect practice

The committee felt that the recommendation would not constitute a change in practice, and that there would not be a resource impact on the NHS.

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