IntroductionCT scan with brain showing signs of stroke
Prevention of AF
Routine population-based screening for persistent AF
Target groups for screening for persistent AF
Conclusion
References

This is part 1 of a two-part article.

Part 2 can be found here. 

 

 

  

 

Introduction

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

 

Age-specific prevalence of atrial fibrillation from various studies

Prevention of AF

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.

 

Routine population-based screening for persistent AF

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
COST CONSIDERATIONS
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.

 

Target groups for screening for persistent AF

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.

 

 Strategies for AF prevention and screening

 

Conclusion

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).

 

J James
M Fotherby
A.K. Mistri
University Hospitals of Leicester NHS Trust

Conflict of interest: none declared

 

References

1. Wilke T, et al. Incidence and prevalence of atrial fibrillation. Europace 2013; 15: 486–93

2. JMG Wilson and G Jung; Principles and Practice of Screening for Disease, World Health Organization, 1968

3. January CT, et al. AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation: Executive Summary. Journal of the American College of Cardiology 2014; 64 (21): 2246–80

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

8. Kirchhof P, et al. 2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS. Eur Heart J 2016; 37 (38): 2893–2962

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)

10. Macle L, et al. Focused Update of the Canadian Cardiovascular Society Guidelines for the Management of Atrial Fibrillation. Canadian Journal of Cardiology 2016; 32: 1170–85

11. Moran PS, et al. Effectiveness of systematic screening for the detection of atrial fibrillation. Cochrane Database of Systematic Reviews 2013, Issue 4