AF screening and diagnosis

Atrial fibrillation symptoms

Atrial fibrillation (AF) patients can present with a wide range of symptoms; however, these can be non-specific and a poor guide for AF diagnosis

AF patients may present with heart failure, myocardial infarction or another acute coronary syndrome (ACS), stroke or haemodynamic collapse, and a variety of other typically non-specific symptoms (Figure 1)¹.

Figure 1. Common atrial fibrillation symptoms (Adapted²).

However, 12% to 33% of AF patients are asymptomatic^3,4. On the other hand, AF patients often experience debilitating symptoms despite treatment (Figure 2)³.

Figure 2. Prevalence of atrial fibrillation symptoms despite treatment (Adapted²).

Women tend to experience worse AF symptoms

Women tend to develop more frequent and severe AF symptoms than men.

Women show longer paroxysmal episodes, and the ventricular response rates during paroxysmal episodes are faster in women than among men⁵The European Society of Cardiology (ESC) and the European Heart Rhythm Association (EHRA) guidelines recommend using the modified EHRA symptom scale (Table 1) to quantify the symptomatic burden in clinical practice². However, their non-specific nature makes symptoms alone an unreliable guide to diagnosis.

Table 1. Modified European Heart Rhythm Association (EHRA) scale for atrial fibrillation symptoms (Adapted²). AF, atrial fibrillation.

Atrial fibrillation screening

Professor John Camm (London, UK) discusses the importance of detecting atrial fibrillation (AF) early.

Professor Tatjana Potpara, co-author of the 2020 European Society of Cardiology atrial fibrillation guidelines, discusses the benefits of screening for AF, and the tools and strategies currently available for screening. Additionally, Professor Potpara considers the evidence for whether treatment of screen-detected AF translates to beneficial outcomes for patients.

Asymptomatic AF is associated with increased risk of stroke and mortality compared with symptomatic AF⁶. Observational data suggest that screen-detected AF responds to treatment similarly to AF detected by routine care⁷.

Therefore, international initiatives to implement screening for AF in clinical practice are increasing. This is not only due to high prevalence of asymptomatic AF, but also to the overall increasing AF prevalence, previously unknown AF detection in about 10% of all ischaemic strokes, potential to prevent AF-related strokes with appropriate management, and increasing availability of screening tools².

In 2020, the European Society of Cardiology (ESC) published guidelines for the diagnosis and management of AF². The ESC recommendations for AF screening and diagnosis are summarised in the infographic below.

Atrial fibrillation screening tools

The tools that can be used for AF screening are:

• Patient- or healthcare professional-initiated oscillometric blood pressure cuff
• Pulse auscultation
• Patient-initiated photoplethysmogram on smartphone
• Semicontinuous photoplethysmogram on a smartwatch or wearable device
• Patient- or healthcare professional-initiated intermittent electrocardiogram (ECG) rhythm strip using smartphone or dedicated connectable device
• Intermittent smartwatch ECG initiated by semi-continuous photoplethysmogram with prompt notification of irregular rhythm or symptoms
• Wearable belts for continuous recording
• Stroke unit/in hospital telemetry monitoring
• Long-term Holter
• 1–2 week continuous ECG patches
• Implantable cardiac monitors

Regardless of the tool used, when AF is detected by screening, a single-lead ECG tracing of ≥30 seconds or 12-lead ECG showing AF analysed by a physician with expertise in ECG rhythm interpretation is necessary to establish a definitive diagnosis of AF.

The Apple Heart and the Huawei Heart Studies on atrial fibrillation

The Apple Heart study⁸ included 419, 297 self-enrolled smartwatch app users (mean age 40 years) in the USA, of whom 0.5% received an irregular pulse notification (0.15% of those aged <40 years, 3.2% among those aged >65 years). Subsequent 1-week ECG patch monitoring revealed AF in 34% of monitored participants.

The Huawei Heart study⁹ included 187, 912 individuals (mean age 35 years, 86.7% male), of whom 0.23% received a ‘suspected AF’ notification. Of those followed up, 87.0% were confirmed as having AF, with the positive predictive value of photoplethysmography signals being 91.6% [95% confidence interval (CI) 91.5 - 91.8]. Of those with identified AF, 95.1% entered an integrated AF management programme using a mobile AF App (mAFA).

Risks and benefits of atrial fibrillation screening

There are potential advantages and disadvantages in performing AF screening, as summarised in figure 3.

Figure 3. The risks and benefits of atrial fibrillation screening (Adapted²). AF, atrial fibrillation; ECG, electrocardiogram; OAC, oral anticoagulant; SE, systemic embolism.

According to the latest ESC guidelines², when screening for AF it is recommended that the individuals undergoing screening are informed about the significance and treatment implications of detecting AF. In addition, a structured referral workflow should be in place for screen-positive cases for further physician-led clinical evaluation to confirm the diagnosis of AF and provide optimal management of patients with confirmed AF.

No country has yet established a national screening programme for AF¹⁰. However, there is increasing evidence suggesting that screening is beneficial, especially in high-risk populations (for example, the elderly). On the other hand, further evidence and randomised trials are needed to consolidate whether or not AF screening is effective at reducing cardiovascular morbidity and mortality¹⁰.

In terms of healthcare costings, higher AF-related medical costs related to AF underdiagnosis justify screening strategies to help identify and treat AF early¹¹.

Atrial fibrillation diagnosis

Electrocardiogram (ECG) monitoring remains the gold-standard method for diagnosing atrial fibrillation (AF).

In this video, Professor Tatjana Potpara, from the School of Medicine, University of Belgrade in Serbia, emphasises that although screening devices play an important part in detecting AF, diagnosis of AF can only be established if confirmed by an ECG recording assessed by a physician.

The diagnosis of AF requires rhythm documentation with ECG tracing showing AF; by convention, an episode lasting at least 30 s is diagnostic for clinical AF²

Clinical and subclinical atrial fibrillation

Clinical AF can be symptomatic or asymptomatic and it is defined as AF documented by surface ECG.

Subclinical AF or atrial high-rate episodes (AHRE) refer to individuals without symptoms attributable to AF, in whom clinical AF is not previously detected (no surface ECG tracing of AF). Subclinical AF or AHRE are usually detected by implanted devices and wearables.

Literature suggests wearables may be useful for longer, non-invasive monitoring to detect AF¹². Wearables assist in diagnosis, behaviour changes and self-monitoring but adoption of wearables is dependent on factors like overcoming the barriers of use by improving device accuracy; promotion and support from providers; and increased short-term investment to upskill staff¹³.

Clinical atrial fibrillation types

An irregular pulse should raise a suspicion of AF: the sensitivity and specificity of pulse rate for AF is 94% and 72%, respectively^1,4. Clinical presentation (Table 2) may indicate the type of AF, although about a third of AF episodes are asymptomatic^2,4.

Table 2. Presentation of different clinical types of atrial fibrillation (Adapted²). AF, atrial fibrillation.

An ECG is the gold-standard method to diagnose AF (Figure 4)⁴. In addition, all AF patients should undergo a comprehensive evaluation, including accurate history, clinical examination and assessment of comorbidities and risk factors².

Figure 4. Electrocardiogram showing normal sinus rhythm, atrial fibrillation, and differential diagnoses (Adapted¹⁴).

Typically, ECGs of AF typically do not show a distinct P wave^1,5. Rather the electrical activity is disorderly (fibrillatory) with irregular R-R intervals^1,5. Heartbeat is erratic and rapid, typically 90–170 beats per minute, reflecting the irregular ventricular activation. Unless the patient has other cardiac conduction disorders, the QRS complex tends to be narrow¹. Clinicians should consider Holter monitoring (using a portable device for 24 to 48-hour cardiac monitoring) in patients presenting with palpitations¹⁵.

Screening with a 7-day ECG patch reveals that older women with an elevated CHARGE (Cohorts for Heart and Aging Research in Genomic Epidemiology)-AF score had a high prevalence of AF¹⁶.

Atrial fibrillation diagnostic recommendation

As AF can develop for the first time after a stroke, guidelines published by the European Society for Cardiology (ESC) and the European Heart Rhythm Association (EHRA) state that diagnosis of AF requires a standard 12-lead ECG recording or a single-lead ECG tracing of ≥30 seconds showing a heart rhythm with no discernible repeating P waves and irregular R-R intervals (when atrioventricular conduction is not impaired)².

In addition, the ESC/EHRA guidelines recommend²:

• opportunistic AF screening by measuring the pulse or from an ECG rhythm strip in patients older than 65 years of age 
• regularly interrogate pacemakers and implantable cardioverter defibrillators for atrial high-rate episodes (AHREs); if present, patients should undergo additional ECG monitoring to detect AF
• considering systematic ECG AF screening in patients older than 75 years of age or at high stroke risk
• using transthoracic echocardiography, which can assess valvular heart disease and exclude intracardiac thrombi, to guide management with early cardioversion or catheter ablation 
• considering long-term ECG monitoring to assess rate control in people with symptomatic AF
• considering long-term ECG monitoring to correlate symptoms with AF episodes and differentiate proximal and persistent AF

The ECG/EHRA guidelines recommend that patients are informed about the significance and treatment implications of AF and receive a structured referral platform to confirm the diagnosis and provide optimal management)².

Atrial fibrillation underdiagnosis

As up to 23% of people with cryptogenic strokes and transient ischaemic attacks (TIAs) show paroxysmal AF on long-term ECG monitoring, the burden imposed by AF-related stroke may be underestimated¹⁷. Further evidence suggesting underdiagnosis emerged in a study that implanted a cardiac monitor in 385 patients with a CHADS₂ score, a previous version of the CHA₂DS₂-VASc scoring system for assessing stroke risk, of 3 or greater or 2 with at least one additional risk factor. Of these, 90.4% experienced non-specific symptoms that might arise from AF, including fatigue, dyspnoea and palpitations¹⁸.

In an intervention study, 1127 people aged ≥65 years and with no prior history of AF completed self-screening. AF was diagnosed in 49 people and 44 of them had a CHA₂DS₂-VA of ≥2 suggesting that self-screening could reduce the risk of stroke¹⁹.

The detection rate of AF lasting six or more minutes rose from 6.2% at 30 days to 29.3% at 18 months and 40.0% at 30 months (Figure 5). Moreover, at 18 months 24.2% and 12.0% of patients experienced episodes lasting at least one hour and at least six hours a day respectively. AF incidence at 18 months was similar among patients with CHADS₂ scores of 2 (24.7%), 3 (32.7%) and at least 4 (31.7%)¹⁸.

Figure 5. Incidence of undiagnosed atrial fibrillation during insertable cardiac monitoring (Adapted¹⁸). AF, atrial fibrillation; ICM, insertable cardiac monitoring.

A study in nationwide cohort of 19.5 million individuals revealed that diagnosis of new AF decreased by 35% (95% CI: 21%–48%) from 1.14 per 1000 individuals (95% CI: 1.05–1.24) to 0.74 per 1000 (95% CI: 0.64–0.83, p-value<0.001) after onset of the COVID-19 pandemic²⁰.

Atrial fibrillation differential diagnosis 

Clinicians need to be aware of illnesses and comorbidities that may contribute to or be associated with AF (Figure 6).

Figure 6. Common conditions (brown) and comorbidities (blue) linked to atrial fibrillation (Adapted³). AF, atrial fibrillation; TIA, transient ischaemic attacks.

Indeed, only between 2% and 12% of AF patients do not have underlying heart disease (previously known as lone AF)³. A quarter of AF patients have overt cardiac disease, while a third have three or more comorbidities, some of which may be risk factors for stroke³. The ESC/EHRA guidelines offer specific guidance for AF management in people with diabetes, obesity, sleep apnoea, and other respiratory diseases and chronic kidney disease (CKD)².

The differential diagnosis should include non-cardiac causes of AF, such as¹:

• adverse events, such as antiarrhythmic drugs (AADs), beta-agonist bronchodilators and lithium
• collagen vascular disease
• electrolyte abnormalities
• hypothermia
• infiltrative cardiomyopathies
• pulmonary embolism, COPD, cor pulmonale, sleep apnoea and other respiratory conditions
• supplements (such as diet pills) and illicit drugs
• thyroid disease

More on treatment goals and strategies for AF

Atrial fibrillation comorbidities and risk factors

Professor John Camm (London, UK) discusses the management of risk factors for atrial fibrillation (AF).

Several comorbidities and risk factors contribute to AF and the risk of stroke. These modifiable comorbidities and risk factors seem to promote AF development and maintain the arrhythmia (Figure 7)⁵.

Figure 7. Examples of modifiable comorbidities that seem to promote atrial fibrillation development and maintain the arrhythmia (Adapted⁵).

For instance, AF is associated with a 3-fold increase in the likelihood of developing congestive heart failure (CHF) and the prevalence increases with worsening New York Heart Association (NYHA) functional class. CHF risk is higher in people with permanent AF than those with persistent AF. In turn, CHF risk is higher in people with persistent than paroxysmal AF.

Patients with AF and CHF show a poorer prognosis than with either alone⁵

Therefore, risk factor modification is an important component of AF management⁵. For instance, a study that followed patients for 5 years after experiencing an AF-related stroke, reported that statins reduced mortality by 48%²¹.

More on treatment goals and strategies for AF

References

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