Atrial fibrillation (AF) is a growing public health problem in Ireland. The prevalence of AF increases significantly with age. In Ireland, substantial increases in the cohort 65 years of age and over are predicted, with increases in the population of over-80s by two-thirds by 2021.¹ Preliminary results from The Irish Longitudinal Study on Ageing (TILDA) estimate that prevalence of AF is 3.2% of the total population aged over 50, with 5.3% in the over-65s and almost 11% in those aged over 80 years old.² It is estimated that 50,000 people in Ireland have AF, 40% of whom are unaware of their condition. Preliminary results also reveal a prevalence rate in Ireland greater than that experienced by our European neighbours.²

Figure 1: There are no distinct P-waves evident, some irregular activity may be seen(click to enlarge)

Figure 2: The 48 hours is of clinical importance. After this the chances of spontaneous cardioversion is low and anticoagulation must be considered (Source: Europace © 2010 Oxford University Press)(click to enlarge)

Detection and diagnosis

AF is defined as an arrhythmia with the following characteristics:

• The surface electrocardiogram (ECG) shows ‘absolutely’ irregular R-R intervals
• There are no distinct P-waves evident, some irregular activity may be seen (see Figure 1).

The problem of early recognition of AF is greatly aggravated often by the silent nature of the rhythm disturbance. An irregular pulse should always raise the suspicion of AF, but an ECG recording is necessary to diagnose AF. Any arrhythmia that has the ECG characteristics of AF and lasts sufficiently long for an ECG to be recorded, or 30 seconds on a rhythm strip, should be considered as AF.

In patients with suspected AF, a 12-lead ECG is recommended as the first step to establish the diagnosis. Clinical symptoms such as palpitations or dyspnoea should trigger ECG monitoring to demonstrate AF.

It is possible to identify different types of AF based on presentation and duration of the arrhythmia from first diagnosed to permanent AF. Every patient who presents with AF for the first time is considered a patient with first AF irrespective of the duration of the arrhythmia. Paroxysmal AF, while self-terminating usually within 48 hours, may continue for up to seven days. The 48 hours is of clinical importance. After this the chances of spontaneous cardioversion are low and anticoagulation must be considered (see Figure 2).

Silent AF may manifest as an AF-related complication (eg. ischaemic stroke) or may be diagnosed by an opportunistic ECG.

Initial management and treatment

Management of AF is aimed at reducing symptoms and preventing complications. Prevention of AF-related complications relies on anti-thrombotic therapy, control of ventricular rate, and adequate therapy of concomitant cardiac disease. 

The European Society of Cardiology (ESC) recommendations for clinical management of AF involve five objectives:³

• Prevention of thromboembolism
• Optimum management of concomitant cardiovascular disease 
• Symptom relief 
• Rate control
• Correction of the rhythm disturbance.

AF and stroke risk

In population studies, AF has been associated with a fivefold risk of stroke independent of other vascular risk factors.⁴ Many studies have indicated that 20-30% of all strokes are attributed to AF, both in Ireland and internationally. Ischaemic strokes associated with AF are often fatal. Two-thousand deaths annually are caused by stroke in Ireland, 30% of these deaths are AF stroke-attributable deaths. 

Those patients who survive are left more disabled by their stroke and the percentage of severe strokes is three times higher in AF strokes compared to non-AF strokes.⁵ They are also more likely to suffer stroke recurrence than patients with other causes of stroke. 

Consequently, the risk of death from AF-related stroke is doubled and the cost of care increased 1.5-fold.^6,7 The North Dublin Population Stroke Study (NDPSS) identified AF in 31% of all incident stroke patients (n = 568), of which 46% were newly diagnosed.⁸ By 2026 it is projected that 44% of all incident strokes will be attributable to AF. 

AF and co-existing vascular risk factors

Many risk factors for AF are shared by other cardiac conditions that in turn predispose to the occurrence of AF. The primordial prevention of the risk factors would jointly prevent their emergence and in turn the AF they promote. Of the major cardiovascular risk factors investigated by the Framingham Study, hypertension and diabetes were significant independent predictors of AF.⁹

Hypertension is a powerful independent predictor of stroke in AF patients and an important risk factor for developing AF. The strong association between AF, hypertension and stroke could depend on reduced aortic compliance, left ventricular hypertrophy, diastolic dysfunction and left atrial dilatation, giving rise to stasis and thrombus formation.¹⁰

Modifiable risk factors include tobacco use, excessive alcohol consumption, physical inactivity and stress.¹¹ These risk factors are also common to most forms of heart disease and it itself is a risk factor for cerebrovascular, ischaemic heart disease and renal disease. Cigarette smoking is an important risk factor in women adjusting only for age. Obesity is associated with long-term risk of AF, and alcohol abuse is related to occurrence of AF when consumed at sufficiently high amounts. 

Screening for AF

An irregular pulse should always raise the suspicion of AF, but ECG recording is necessary to diagnose AF. Following the introduction to clinical practice of electronic devices to measure blood pressure and pulse rates, it is becoming increasingly more common for clinicians not to systematically feel the pulse. This has potential to reduce detection rates of rhythm irregularities.

Screening for AF in adults aged 65 years and over fulfils many of the Wilson and Jungner criteria for a screening programme.¹² It is a common and important condition that can be diagnosed by means of a simple test (eg. ECG) and the risk of serious sequelae, such as stroke, can be dramatically reduced by treatment. 

In population terms, AF is an important risk factor for stroke, and anticoagulation provides a highly effective treatment to reduce this risk. It has been estimated that the optimal treatment of AF in the population might reduce the overall incidence of stroke by 10%. 

Population screening for AF in adults 65 years and older in the general practice setting has been shown to be effective in the detection of new cases. Evidence suggests that opportunistic screening is the preferred model of care. This includes opportunistic pulse-taking, prompted by flagged case notes in adults 65 years of age and older during routine clinic attendances and subsequent 12-lead electrocardiography (ECG) on those with an irregular pulse. 

This preventative strategy was demonstrated to be as effective as systematic population screening, with both being more effective than ‘routine practice’.¹³ This suggests that routine electrocardiography within this population is unnecessary for the detection of AF as long as healthcare professionals are conscientious about feeling the pulse. 

Stroke risk reduction by anticoagulation therapy

The risk of stroke associated with AF is reduced by up to 67% by anticoagulant prophylaxis, usually with warfarin.¹⁴ However, despite evidence of substantial benefit, under-utilisation of anticoagulation remains very common.

In the NDPSS, of those with pre-existing AF, 28% were on oral anticoagulation therapy (OAC), 55% were on antiplatelet therapy and 17% were on no treatment.¹⁵ In addition, the Irish National Audit of Stroke Care (INASC)  showed that 22% of 2,173 acute stroke patients were known to have AF, of whom 26% were on warfarin, 57% were on antiplatelet therapy and 22% were on neither.¹⁶

Internationally, many studies have reported similar findings. For example, in the Canadian Stroke Network¹⁷ only 40% of AF patients considered eligible were on anticoagulation therapy at the time of stroke, and the SAFE II trial has shown that less than 25% of patients with non-valvular AF admitted for stroke were previously receiving OAC, although approximately 70% would have been eligible.

International studies have found that various factors contribute to non-prescribing of anticoagulation therapy in patients with AF. Warfarin therapy is associated with risk of haemorrhage, which may be major and occasionally fatal. 

For this reason, the decision to begin warfarin in a patient with AF is often difficult, particularly in older individuals who may be frail, or have a complex medical history, recent falls, or other factors which may cause concern for increased risk of major bleeding complications. 

Stroke risk assessment

A cornerstone of managing patients with AF is deciding whether or not to prescribe an anticoagulant. To help clinicians decide on which management path to choose, several tools have been developed to estimate the risk of stroke on the basis of clinical factors.^18,19

International guidelines stress the importance of risk assessment of patients with AF for anticoagulation therapy. The CHA₂DS₂-VASc risk scheme devised by Dr J Cam is recommended by the European Society of Cardiology in the 2010 guidelines for atrial fibrillation.³ Previously the CHADSsub₂ index and acronym representing congestive heart failure, hypertension, age over 75, diabetes and previous stroke was endorsed and is currently widely used and is easily applied in general clinical practice.²⁰ The CHAsub₂DSsub₂-VASc score differs from the CHADSsub₂ in that age is weighted differently. 

In addition, CHAsub₂DSsub₂-VASc considers female sex and a history of vascular disease to be significant risk factors for stroke. By implementing the CHAsub₂DSsub₂-VASc, increasing numbers of patients with AF will be offered anticoagulation.

Anticoagulation 

Currently warfarin is the anticoagulation drug available and reimbursed by the HSE. The British Society of Haematology has a recommended dosing algorithm.²¹

Two drugs have recently been licensed for anticoagulation in AF patients for stroke prevention. Dabigatran is an oral anticoagulant which binds directly and reversibly to thrombin to inhibit its actions, thereby interrupting the formation of blood clots. Rivaroxaban is a highly selective direct factor Xa inhibitor with oral bioavailability. Inhibition of Factor Xa interrupts the intrinsic and extrinsic pathway of the blood coagulation cascade, inhibiting both thrombin formation and development of thrombi.

They are not yet available to all AF patients under the HSE reimbursement schemes. With these new drugs it is important for clinicians to be cognisant of the continuing need for patient review and education regarding compliance and the precautions necessary to prevent haemorrhage. 

Burden of AF 

In 2010, AF was associated with 8,100 admissions; 5,203 of these were through our emergency departments. These admissions accounted for 34,583 bed days, 4,280 of which were intensive care bed days. A new study carried out by Hannon et al on the NDPSS data found that the total cost of stroke was almost 40% higher for any inpatient with AF stroke compared to non-AF stroke.¹⁵ It also indicates that the cost of AF-attributable stroke is €56,000 per patient, which cumulatively would result in a cost to the HSE of €117,600,000. This is based on 2,100 AF-associated strokes per year. The main drivers for the higher costs associated with AF-stroke of all types is the cost of inpatient care.¹⁵

In conclusion, AF is currently and will continue to increasingly give rise to significant economic and social burden to our health system and population. It can be easily diagnosed as long as healthcare professionals are conscientious in regard to feeling the pulse. Appropriate treatment with anticoagulation can prevent significant morbidity and mortality as a result of AF-related stroke.

References

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