Can the NICE guidelines on the management of atrial fibrillation improve its management?

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia seen in clinical practice. The incidence of AF increases significantly with advancing age, with the prevalence being 8% for population of age 80 and above.¹ For those who are 40 years and older, the lifetime risk for the development of AF is 1 in 4 in both men and women.^2,3 With an ageing population, an increase in the incidence and prevalence of AF has been reported worldwide.^4,5 Indeed, AF has become such a common problem that it is now described as ‘a major epidemic’.

Due to the close relationship between AF, stroke and thromboembolism there has been a need for increased caution. Irrespective of applying a rate-control or rhythm-control strategy thromboprophylaxis remains the essential core of any AF management strategy. Given that AF is so common various management guidelines have been published over the last few years.^6,7 In the UK, the evidence-based national guidelines for the management of AF were published by the National Institute for Health and Clinical Excellence (NICE) in June 2006.⁷ The methodology for the NICE guidelines differs from other expert consensus-based guidelines in that, following agreement and definition of a scope for the NICE guideline, pertinent questions on AF management are formulated and a formal systematic review undertaken by an information scientist who would retrieve, assess and organise sources of published evidence. The latter is then critically appraised and graded by a health service research fellow and, if needed, a health economist. The synthesised evidence is reviewed and debated by a guideline development group (GDG), which included multidisciplinary representatives from various learned bodies and specialist organisations.

Despite the published guidelines for the management of AF, this common arrhythmia remains poorly managed, both in primary and secondary care, with marked variation in the approach to investigation and treatment. Apart from the specific recommendations, the NICE guidelines have highlighted five key priorities for implementation as well as audit criteria and areas for future research (Box 1). The remit of the NICE guideline on AF management was to provide a practical, pragmatic and highly applicable national guideline to the UK clinical setting, which would be applicable for >80% of AF patients for >80% of the time. Given this aim, has the publication of these guidelines actually improved AF management?

In the current issue of Clinical Medicine, the paper by Loo and colleagues examines existing clinical practice in advance of publication of the NICE guidelines.⁸ Their study suggests that only 84% of 131 patients with diagnosis of AF had either electrocardiogram (ECG) documentation in primary and/or secondary care. Almost half of the patients with AF were managed in primary care alone and the diagnosis of AF was generally accurate. The use of echocardiography is an important part of management, and in the paper by Loo et al only 44% of the study population underwent an echocardiogram.⁸ However, this percentage increases in those who were diagnosed with AF after 2000 and those who had cardiology input from secondary care. This could probably be explained by a better understanding of the management of AF, better educational efforts and, perhaps, a better provision of echocardiography services from secondary care.

The overall rate of anticoagulation was higher than other studies, but there remains a discrepancy, with only about half of patients in the ‘high-risk’ group, according to NICE guidelines for thromboembolic risk, being prescribed warfarin.^9,10 When comparing the NICE stroke risk score with the CHADS2 score, Loo and colleagues found that 50% of the patients recruited fell into the ‘high-risk’ category using the NICE schema, while only 28% of the same patients would be considered to be ‘high risk’ if the simpler CHADS2 scoring schema was used, despite the latter being published earlier (2001) than the NICE schema.⁸

Also, the large number of patients categorised in the intermediate/moderate-risk group by the CHADS2 schema reflects the limitation of the published stroke risk stratification schema in assisting clinicians’ antithrombotic therapy decision making. In the recent Stroke in AF working group analysis, the proportion classified as high risk could vary substantially – between 11% and 77% – depending on which schema was used.¹¹ Given that current AF management guidelines recommend the use of either warfarin or aspirin in the intermediate-risk patient group, this potentially leads to the dilemma of whether anticoagulant therapy or aspirin should be used, and may create indecision for clinicians managing such patients.¹² Also, the predictive value of various schema for stroke events is modest (C statistic values approximately 0.60–0.65) and efforts to improve this are clearly needed.¹³

To illustrate this issue, a cut-off point of age >75 is probably too simplistic, given that there is a relative risk for stroke of 1.5 per decade with increasing age, as documented by the AF working group.¹⁴ The recent Birmingham Atrial Fibrillation Treatment of the Aged (BAFTA) study, which considered patients with AF aged ≥75 years in the primary care setting, also showed that warfarin was significantly more effective than aspirin in preventing stroke (by over 50%, with nearly 2% annual absolute risk reduction), without any excess in the risk of major bleeding.¹⁵ Similarly, ‘hypertension’ as one of the criteria in the CHADS2 schema is ambigious, given that history of hypertension (but now well controlled) may well carry a different stroke risk to uncontrolled hypertension. In an analysis from the SPORTIF trial dataset, for example, there was a clear difference in stroke and systemic embolism with poorly controlled hypertension, compared to well-controlled blood pressure levels.¹⁶ Indeed, stroke events were low and fairly constant when mean systolic blood pressure was < 140 mmHg, but when levels exceeded this threshold, event rates for stroke and systemic embolism rose substantially.

Thus, there remains scope for better use of stroke risk stratification and improvements in the current schema to target stroke and thromboembolism prophylaxis appropriately, and a need for refinement of subjects classified at intermediate risk. Clearly, the article by Loo and colleagues illustrates that AF in general is still relatively poorly managed in primary and secondary care despite well-established principles and protocols.⁸

Can the NICE guidelines for the management of AF overcome this issue and ultimately improve patient care? Guidelines are simply recommendations for best practice given the best evidence available at the time. Indeed, new data mean that some recommendations in the NICE guidelines need to be revisited. For example, NICE suggest that rhythm control may be the best initial option for subjects with congestive heart failure. However, the AF–congestive heart failure trial recently reported that there was no significant difference in a rate control or rhythm control strategy for patients with AF and associated heart failure.¹⁷ Also, new antiarrhythmic drugs, such as dronedarone, may well change the approach to rhythm control, for cardioversion of AF and the maintenance of sinus rhythm.¹⁸ The BAFTA trial has also shown that elderly AF subjects aged ≥75 years would substantially benefit from anticoagulation therapy rather than aspirin, and even the NICE stroke risk stratification schema may need refinement to reflect this new evidence.¹⁵ New oral anticoagulants, such as the oral direct thrombin inhibitors and oral factor Xa inhibitors, are on the horizon, and may also revolutionise the approach to providing thromboprophylaxis in AF, and even remove the confusion for moderate-risk subjects with AF, as a safe anticoagulant without the necessity for monitoring could well be prescribed for all those AF patients at moderate to high risk of stroke, thus avoiding the ambiguity of published stroke risk stratification schema and the perception that aspirin is a true alternative to anticoagulation for stroke prevention in patients with AF.

Clearly, revisions to the NICE guidelines for AF management may soon be needed. For now, at least, the guidelines provide a backbone of evidence-based medicine for clinicians in the UK in the management of AF.

• © 2009 Royal College of Physicians