Atrial fibrillation affects more than 2.4% of the population. AF-related stroke is a major cause of physical and cognitive disability, and mortality. This article summarises the current recommendations and suggested strategies for AF screening in the general population. This is part one of a two-part series. Part two of the article will review screening for paroxysmal AF.
This is part 1 of a two-part article.
Part 2 can be found here.
Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia affecting about 2.4% of the UK population, with approximately half being undiagnosed. Public Health England (2015) estimates indicate an average GP surgery case burden of 174 (61 undiagnosed). There is a striking increase in prevalence with age, from <3% in the under 60s to >10% in the over 75s (see Figure 1).1
AF is a major risk factor for stroke, increasing the risk five-fold, and about one in five strokes is attributable to AF, increasing to one in two in older age groups. AF-related strokes are more severe, reflected on brain imaging as large cortical infarcts, with a high risk of death (one in four) and residual disability in the majority of survivors. Other complications include: non-stroke systemic embolism, cardiac failure, increased hospitalisation, reduced quality of life, and cognitive decline leading on to vascular dementia.
AF-related stroke satisfies standard criteria for screening,1 as summarised in Table 1. Given the significant societal implications, there needs to be a very good reason for us to “not undertake” screening programs for AF. The importance of prevention of AF-related stroke cannot be over-emphasised.2
Prevention of AF is already undertaken in various settings, and is one of the objectives of treating vascular risk factors like hypertension, diabetes and coronary artery disease. It is also one of the goals of lifestyle modification changes like smoking cessation, alcohol moderation and weight loss (in the context of obesity). Optimal targets should be targeted, including: BP<130/80mmHg (<140/90 where age >75 years); HbA1c <6.5%. Most risk factors for AF are monitored either in the primary care setting or in specialist clinics, though not necessarily with the primary aim of preventing AF. In addition, regular pulse checks tend to be part of routine practice enabling identification of persistent AF in high risk groups. Screening for persistent AF can usually be undertaken with pulse checks; whilst screening for paroxysmal AF may require longer periods of cardiac monitoring.
AF is potentially suited to screening programs, having a detectable asymptomatic phase with a clearly understood pathophysiology. The natural history of AF is now well recognised. Initial atrial remodelling, secondary to risk factors like hypertension or ischaemic heart disease, leads on to brief paroxysms of fibrillation. Over a period of time, this progresses with longer paroxysms, and finally persistent atrial fibrillation (AF ‘persists’ >seven days). When the duration of this increases beyond 12 months, it is labelled as long-standing persistent (when adopting a rhythm control strategy) or permanent AF (AF is accepted, with no intent to cardiovert).3 AF satisfies Jung’s criteria for disease screening2 (see Table 1).
|TABLE 1. ESTABLISHED CRITERIA FOR ASSESSING SUITABILITY FOR SCREENING A CONDITION2|
|Screening criterion||Relevance to AF & related stroke||Detail|
|KNOWLEDGE OF DISEASE|
|The condition should be important||Yes||Major disability and death|
|There must be a recognisable latent or early symptomatic stage||Yes||Large proportion have asymptomatic AF or non-specific symptoms|
|The natural course of the condition, including development from latent to declared disease, should be adequately understood.||Yes||Well understood natural history from development of risk factors, leading on to paroxysmal, persistent and permanent AF|
|KNOWLEDGE OF TEST|
|Suitable test or examination.||Yes||Universally available ECG|
|Test acceptable to population.||Yes||Non-invasive and quick test|
|Case finding should be continuous (not just a ‘once and for all’ project).||Yes||This should be the case for high risk populations|
|TREATMENT FOR DISEASE|
|Accepted treatment for patients with recognised disease||Yes||Substantial evidence base for potent stroke prevention effect of anticoagulation|
|Facilities for diagnosis and treatment available||Yes||Most primary care surgeries can undertake ECG promptly|
|Agreed policy for whom to treat as patients||Yes||Several guidelines support management of AF (NICE; ESC; ASA) based on objective assessment of risk vs benefit|
|Costs of case finding (including diagnosis and treatment of patients diagnosed) economically balanced in relation to possible expenditures on medical care as a whole||Yes||It may be that screening needs to be targeted at based on risk factors for stroke, focusing initially on the relatively higher risk population eg. CHADSVaSc>1|
There remains ongoing debate about routine screening for AF, which was not recommended by the UK National Screening Committee (2014) based on lack of data on cost-effectiveness and suboptimal management of known AF.4 This is anticipated to be reviewed in 2017–18, alongside a review of the NICE guidelines for AF.5 There would be little utility of identifying AF if stroke prevention interventions (chiefly anticoagulation) would not be indicated despite identification of AF—such as in truly low risk populations, eg. under 65 without vascular disease, where the CHADSVASC Score would be 0.5 However, screening in populations where CHADSVASC Score >=1 is likely to need intervention.
The AF Association and Anticoagulation Europe recommend introduction of a ‘targeted’ national screening programme drawing on routine manual pulse checks and ECG readings,6 though there is no specified definition of ‘targeted’. Thus, the general consensus is that screening the whole population is unlikely to be appropriate or cost-effective; and a targeted approach directed at high-prevalence groups is likely to be the best strategy. It is thus important to clarify which groups should be targeted.
Most secondary care settings already engage in screening, with all hospitalised patients having a pulse check, any pulse irregularity leading on to a standard 12-lead ECG, which is universally available. Similarly, many (but not all) primary care settings have access to an ECG. AF prevention by optimal management of vascular risk factors is already undertaken in specialty clinics (for hypertension; coronary artery disease; cardiac failure; COPD and valvular heart disease). Routine pulse checks should be part of the standard management in such clinics to enable early identification and primary prevention of stroke. Where longer term management has been transferred to primary care, annual monitoring should include pulse checks. All over 75s should have annual pulse checks as screening for AF in primary care, irrespective of comorbidity. Given that guidelines recommend anticoagulation where the CHADSVASC score is 1 or more, an automated method for calculating the score and targeting pulse checks in those with a score >=1 would be ideal.
AF portends a grave prognosis, substantially increasing stroke risk. In the presence of a potent intervention to reduce risk, a program for screening is required. Population-based screening is not considered cost effective, thus targeted screening for AF is recommended as part of a comprehensive approach to stroke prevention in people with AF. It is crucial that identification of AF leads on to appropriate risk assessments to inform anticoagulation decisions.
|TABLE 2. COMMENTS ON AF SCREENING IN VARIOUS GUIDELINES AND POLICY STATEMENTS|
|AF Guideline||Recommendation about screening||Details|
|NICE CG180 June 20145||Yes||Selective pulse checks in the presence of cardiorespiratory symptoms, TIA or stroke.|
|National Screening Committee, UK4||Yes||Recommended against routine screening for AF in the over 65 age group.|
|ESC 20127||Yes||Class Ib recommendation for opportunistic pulse checks in the over 65 age group.|
|ESC 20168||Yes||ECG screening in at-risk populations (especially stroke survivors and the elderly)|
|British Cardiovascular Society9||Yes||Advocates routine screening for AF|
|Canadian Cardiovascular Society10||No||N/A|
|Cochrane Database of Systematic Reviews11||Yes||Single study identified: Opportunistic and systematic screening significantly better than standard practice, and roughly equivalent, with higher cost for systematic screening (£1514 vs £337, per additional case).|
University Hospitals of Leicester NHS Trust
Conflict of interest: none declared
4. UK National Screening Committee July 2014 - http://legacy.screening.nhs.uk/atrialfibrillation (accessed 12th May 2017)
5. Atrial fibrillation: management. NICE CG180 - nice.org.uk/guidance/cg180 (accessed 12th May 2017)
6. Atrial fibrillation: preventing a stroke crisis. Chapter 5: Who is at risk of AF? http://www.preventaf-strokecrisis.org/report/call-to-action (accessed 12th May 2017)
7. Camm AJ, et al. 2012 focused update of the ESC Guidelines for the management of atrial fibrillation: An update of the 2010 ESC Guidelines for the management of atrial fibrillation. Eur Heart J 2012); 33 (21): 2719–47
9. BCS Statement on Screening for Atrial Fibrillation to Prevent Stroke. 31st October 2014. http://www.bcs.com/pages/news_full.asp?NewsID=19792297 (accessed 12th May 2017)