Opportunistic screening for atrial fibrillation
Atrial fibrillation often goes undetected as those who have it can be asymptomatic. As a major risk factor for stroke, it is vital nurses can identify and screen patients at risk
In this article…
- Causes and prevalence of atrial fibrillation
- Current treatment
- Advice on opportunistic screening
Shona Holding is arrhythmia nurse specialist at Leeds Community Healthcare Trust; Craig Russell and Keith Tyndall are arrhythmia nurse specialists at Leeds Teaching Hospitals Trust.
Holding S et al (2013) Atrial fibrillation 1: opportunistic screening for atrial fibrillation. Nursing Times; 109: 30, 12-15.
Atrial fibrillation is the most common arrhythmia and the likelihood of having it increases with age. If left untreated it can lead to heart failure and is a significant risk factor for stroke but risk can be greatly reduced with oral anticoagulation. Many people with AF remain asymptomatic, but the risk of stroke remains the same. Simple screening methods will help detect those at risk. Many of those with a diagnosis and at high risk of stroke remain untreated. This two-part series aims to raise awareness of the importance of early detection and appropriate treatment. Part one discusses the complications linked to AF and explores the nurse’s role in screening; part two will look at management.
- This article has been double-blind peer reviewed
- Figures and tables can be seen in the attached print-friendly PDF file of the complete article in the ‘Files’ section of this page
5 key points
- Atrial fibrillation is the most common arrhythmia and its prevalence increases with age
- AF is a major cause of stroke but if treated with an anticoagulant the risk is significantly reduced
- Stroke risk remains the same whether or not the patient is symptomatic
- Opportunistic screening, using a simple pulse check, is a highly effective method of detecting new cases of AF
- It is important that all nurses in primary and secondary care are aware of the signs of AF and involved in screening methods, and know the importance of signposting patients for timely assessment and treatment
Atrial fibrillation - often identified by a fast and erratic heartbeat - is the most common form of arrhythmia. It affects at least 1.7% of the general population; this rises with age, affecting at least 10% of those aged over 75 (Lip and Lim, 2007).
Untreated AF can lead to heart failure and is a significant risk factor for stroke. AF-related strokes tend to be more severe compared with other causes, resulting in greater disability or mortality (Miller et al, 2005). Individuals can be affected by AF to varying degrees but the stroke risk is the same whether they are symptomatic or not. AF-related strokes are preventable; the risk of stroke can be greatly reduced by anticoagulation therapy (Hart el al, 2007).
AF is often diagnosed when patients present with debilitating symptoms in those who are asymptomatic, but it may go undetected and untreated, exposing them to severe consequences that could be preventable. More worryingly, even after AF is detected, many individuals at high risk of stroke remain untreated (National Institute for Health and Clinical Excellence, 2006). Despite recognition of this, recent data suggests anticoagulants are still underused (Cowan et al, 2013), so it is important all nurses - be they hospital or community based - are aware of the signs of AF. Nurses should be involved in screening and know the importance of signposting patients for timely assessment and treatment.
AF occurs when normal regular impulses initiated in the sinus node are overridden by disorganised, chaotic electrical activity in the atrial tissue (Fig 1). This leads to irregular conduction to the ventricles resulting in an irregular heartbeat. AF can be identified clinically by a simple pulse check and confirmed with a 12-lead electrocardiogram (ECG; Fig 2); P waves are absent and the ventricular rate is irregular (Grubb and Newby, 2004).
Causes of AF
A number of factors can contribute to AF development (Box 1). It may be associated with other arrhythmias such as atrial flutter; early treatment of such arrhythmias can reduce the incidence of AF (Prystowsky, 1995). Atrial flutter is similar to AF in that it poses the same risk of stroke, so those with atrial flutter should be risk assessed in the same way. A number of AF cases occur in those aged under 65, with no obvious cause. This is known as “lone” AF (Fuster et al, 2011). AF can also run in families - “familial AF” - which is thought to be a more common factor than previously recognised.
Given that AF is a progressive disease, the European Society of Cardiology has defined five types or temporal patterns (Camm, 2010; Box 2). Identifying the type of AF a patient has helps in developing the most appropriate treatment plan.
Complications of AF
Around two-thirds of those with AF will experience symptoms, the severity of which varies. Extreme cases can result in acute hospital admission but most patients may present to their GP with general malaise and mild breathlessness (Williams et al, 2001). Some may present with breathlessness, palpitations, chest pain and, on rare occasions, syncope. Some experience polyuria during AF; this is associated with the release of atrial natriuretic peptide during atrial stretching and affects long-term regulation of blood volume and arterial pressure (Fuster et al, 2006).
Symptoms are often due to a rapid ventricular rate that can exceed 160bpm. If left untreated it can lead to impairment of ventricular function and subsequent dilatation of the ventricles - termed tachycardia-induced cardiomyopathy (Navas, 2003).
The aim of initial treatment is to reduce the heart rate and alleviate symptoms. Patients are assessed for their suitability for drug therapy such as beta-blockers or calcium-channel blockers for ventricular rate control. A rhythm control strategy is then considered if the patient remains symptomatic (Camm, 2010). This may be pharmaceutical or electrical cardioversion (Fig 3). Treatment will be discussed further in part two of this series.
During AF, disorganised atrial contraction can lead to blood stagnating and collecting in a small pouch in the wall of the left atria, known as the left atrial appendage. This applies to most, but not all, cases. This reduced blood flow can cause thrombus formation, which can dislodge and travel through the blood to the brain resulting in an ischaemic stroke or transient ischaemic attack TIA (Fuster et al, 2006). AF-related strokes tend to be more severe than strokes with other causes due to the size of embolus emerging from the left atrial appendage; this leads to higher death rates, greater disability, and increased health service costs (Stewart et al, 2004; Stewart et al, 2001).
Patients with AF are five times more likely to experience a stroke than those without (Markides and Schilling, 2003) but this risk can be significantly reduced if AF is diagnosed and treated promptly with an anticoagulant such as warfarin (Hart et al, 2007). Anticoagulants are known to reduce stroke risk by 60-70%; aspirin reduces risk by around 22% only (Hart et al, 2007).
Warfarin is the gold standard for stroke prevention but is a complex agent with many drug interactions and potential contraindications. This reduces the number of patients to whom it is prescribed, so its effectiveness is limited. Its underuse is confirmed by NICE (2006), which estimates half of those with AF and at high risk of stroke are not prescribed appropriate treatment. This is a major concern given the evidence for the effectiveness of warfarin, particularly in older people, which was confirmed by the Birmingham Atrial Fibrillation Treatment of the Aged trial (Mant et al, 2007). That study showed there was no difference in rates of major haemorrhage between those treated with warfarin and those treated with low doses of aspirin (75mg).
The availability of new novel oral anticoagulants (NOACs) - for example: dabigatran, a direct thrombin inhibitor; and rivaroxaban and apixaban, both factor Xa inhibitors - will hopefully provide greater scope to treat patients and optimise stroke prevention. Once again, these agents are complex, with advantages and disadvantages over warfarin. Careful consideration must be made when selecting the most appropriate agent for a patient. More information about NOACs will be given in part two of this series.
It is important that patients with a new or existing AF diagnosis have their stroke risk assessed. The European Society of Cardiology provides the most recent guidance on assessing stroke risk in patients with AF (Camm, 2010). CHADS2 (Table 1) and CHA2DS2-VASc (a refinement of CHADS2) (Table 2), are validated stroke risk stratification schemes that are easy to use. The CHADS2 (congestive heart failure, hypertension, age, diabetes, prior stroke) score is now part of the new AF Quality and Outcome Framework indicators for 2012-13 (NHS Employers, 2012).
All patients who have AF should be considered for anticoagulation therapy. ESC guidelines suggest that patients with no risk factors can be treated with aspirin (75-325mg daily) or, preferably, no antithrombotic treatment. Those with a CHA2DS2-VASc score of one should be prescribed oral anticoagulation or aspirin 75-325mg once daily. Patients with one major risk factor - for example, valve disease - or a CHA2DS2-VASc score of two or above should be offered anticoagulation therapy (Camm, 2010).
Detecting AF before initial complications occur is a priority for stroke prevention (Camm, 2010). National screening programmes are therefore recommended by stroke specialists to improve the detection of AF (Christie, 2012).
Screening for new diagnosis of AF
As discussed, many individuals with AF will not experience any symptoms (Wyse et al, 2002). This is a major concern as many patients are unaware they are at risk and are not receiving treatment.
It is not unusual for the first diagnosis of AF to be made after the patient presents to hospital with a stroke. Audit data from a rapid-access AF clinic revealed over a third of attendees presented following an incidental finding of AF, who were otherwise asymptomatic. Many were picked up with a simple pulse check and AF was confirmed on ECG (Holding et al, 2009). More importantly, over half were at high risk of stroke and were assessed for their suitability for anticoagulation therapy. This highlights the importance of screening patients at risk of AF.
Opportunistic screening using a simple pulse check is easy to perform and has been demonstrated to be an effective approach (Hobbs et al, 2005). For example, primary care nurses may perform pulse checks in those aged 65 and over, prompted by flagged notes or taken during routine clinic appointments; an irregular pulse can then be followed up with a 12-lead ECG (Fitzmaurice et al, 2007). Similarly, pulse checks at flu-jab sessions have proved beneficial; these patients tend to be in the high-risk category (Campbell and Jackson, 2011).
The regularity of the pulse indicates whether the patient has AF or something less serious, such as an occasional ectopic beat. Any pulse that does not appear to be regular should be followed up with a 12-lead ECG (Campbell and Jackson, 2011). It is important this is performed correctly by a health professional who has received appropriate training and the person interpreting it is deemed competent (Richley, 2013). ECGs are not always easy to interpret and, if in doubt, advice from an expert in this field, such as a cardiologist or an arrhythmia nurse, may help.
Screening patients with an existing AF diagnosis
Several reasons have been cited for the undertreatment of patients with AF, such as reluctance among health professionals to prescribe anticoagulants due to the perceived risks, assumed contraindications and patient reluctance to accept treatment (Cowan et al, 2013). Increased access to education on the benefits of anticoagulation therapy, compared with antiplatelets, would help address this and reduce the prevalence of strokes in patients with AF.
Identifying patients at risk of stroke is important so their suitability for anticoagulation treatment can be considered. The Guidance on Risk Assessment and Stroke Prevention in Atrial Fibrillation (GRASP-AF) tool is now available in England and enables practices to identify patients with an existing diagnosis of AF and to review the risk profile of each individual (Cowan et al, 2013). GRASP-AF can be downloaded from www.improvement.nhs.uk/graspaf and run on any GP practice system.
The GRASP-AF helps practices to:
- Identify patients who are on an AF register;
- Calculate a CHADS2/CHA2DS2-VASc score;
- Highlight patients who have a CHADS2 score greater than one and are taking warfarin;
- Detect recorded reasons for patients not being treated with warfarin.
Participating practices are requested to upload the data to a central server. This provides a national picture; it shows the uptake of anticoagulation therapy has improved since its use, however a significant number of high-risk patients remain untreated. It also shows that antiplatelets continue to be used as an alternative, particularly in older people (Cowan et al, 2013).
Input by specialist arrhythmia teams has improved the uptake of anticoagulants, as demonstrated by findings of a pilot study in South London. GRASP-AF was run with the input and support of an arrhythmia nurse specialist who worked closely with practices providing education and advice. This resulted in an increased uptake of anticoagulants (Wilson and Cruckshank, 2012). GPs, nurse practitioners and practice nurses all have a role in identifying these patients and assessing their suitability for anticoagulation treatment.
Although AF remains a major cause of stroke, improved use of anticoagulation therapy will reduce this risk dramatically. Its high prevalence means most health professionals will encounter a patient with AF at some point. With improved education and support from specialist arrhythmia teams, all nurses will be better equipped to screen patients for AF and assess those with an existing diagnosis using IT tools such as GRASP-AF. Furthermore the tools enable teams to benchmark their practice against local and national data. Collaborative working is key to optimising stroke prevention.
Part two of this series will discuss the management of AF and optimisation of thrombropophylaxsis.
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