Initial Screening Test for Atrial Fibrillation
An electrocardiogram (ECG) is the required initial screening test for atrial fibrillation, with confirmation by a 12-lead, single-lead, or multiple-lead ECG showing at least 30 seconds of heart rhythm without discernible repeating P waves and irregular RR intervals. 1
ECG Requirements for AF Diagnosis
The diagnosis of atrial fibrillation mandates ECG documentation—this is a Class I, Level A recommendation from the European Society of Cardiology. 1 The ECG must demonstrate:
- Duration: At least 30 seconds of recorded rhythm (standard 12-lead ECG captures 10 seconds, while single-lead devices require 30 seconds or more) 1
- Key features: Absence of discernible repeating P waves and irregular RR intervals when atrioventricular conduction is intact 1, 2
- Acceptable formats: 12-lead ECG, single-lead ECG, or multiple-lead ECG devices that provide an actual ECG tracing 1
Important caveat: Non-ECG wearables using photoplethysmography alone are insufficient for diagnosis and should not be used to initiate AF management. 1
Recommended Screening Approach by Population
General Population ≥65 Years
Routine heart rhythm assessment during any healthcare contact is recommended (Class I, Level C) for all individuals aged 65 years and older. 1 This opportunistic screening approach is more cost-effective than offering 12-lead ECGs to everyone. 3
The American College of Cardiology recommends that physical assessment should include evaluation of pulse irregularity, jugular venous pulsations, heart sound variations, and signs of underlying cardiac or pulmonary disease, followed by ECG confirmation. 4
High-Risk Populations
For individuals aged ≥75 years, or ≥65 years with additional stroke risk factors (CHA₂DS₂-VASc risk factors), prolonged non-invasive ECG-based screening should be considered (Class IIa, Level B). 1 This includes:
- Twice-daily single-lead ECG recordings for 2 weeks, or
- Extended ambulatory monitoring, or
- Implantable loop recorders in selected cases 1
Post-Stroke Patients
In patients presenting with ischemic stroke without diagnosed AF, an implantable loop recorder can evaluate for intermittent AF that may have been missed on initial screening. 5 Single ECG will miss cases of paroxysmal AF, which requires longer duration monitoring such as Holter monitoring, cardiac event recorders, or serial ECGs. 3
Screening Methods: Accuracy and Limitations
Pulse Palpation
- Sensitivity: Acceptable for detecting irregular rhythm 3
- Limitation: High false-positive rate, requiring ECG confirmation 3
- Cost: Cheapest screening method 3
Automated ECG Software
- Sensitivity: 0.89 (95% CI: 0.82-0.93) 6
- Specificity: 0.99 (95% CI: 0.99-0.99) 6
- Positive likelihood ratio: 96.6 6
- Critical limitation: Not sensitive enough to be used alone—requires physician review for definitive diagnosis 3, 6
Healthcare Professional Interpretation
- Physicians: Sensitivity 0.91, Specificity 0.96 6
- Nurses: Sensitivity 0.88, Specificity 0.85 6
- Requirement: Definitive diagnosis must be by 12-lead ECG interpreted by someone with appropriate expertise 3
Essential Follow-Up After AF Detection
Once AF is confirmed by ECG, the American Heart Association and American College of Cardiology recommend comprehensive assessment including: 4
- Transthoracic echocardiogram to assess cardiac structure and function
- Laboratory tests: Thyroid function, renal function, hepatic function, complete blood count, glucose/HbA1c 1, 4
- Additional testing as indicated, potentially including exercise testing to evaluate rate control or reproduce exercise-induced AF 4
Common Pitfalls to Avoid
Do not rely on symptoms alone: Approximately 10-40% of people with AF are asymptomatic, and even symptomatic patients may have asymptomatic episodes. 5 The presence or absence of symptoms is not related to incident stroke risk. 1
Do not use aspirin for stroke prevention: Compared with anticoagulation, aspirin has poorer efficacy and is not recommended for stroke prevention in AF. 5
Do not accept wearable device alerts without ECG confirmation: Devices using photoplethysmography require formal ECG documentation before initiating anticoagulation or other AF-specific management. 1