From the Guidelines
For new onset atrial fibrillation in the emergency department, essential laboratory tests should include a complete blood count (CBC), comprehensive metabolic panel (CMP), thyroid-stimulating hormone (TSH), troponin, brain natriuretic peptide (BNP), and coagulation studies (PT/INR). The CBC helps identify anemia or infection that may trigger or worsen atrial fibrillation. The CMP evaluates electrolyte abnormalities, particularly potassium, magnesium, and calcium imbalances, which can precipitate arrhythmias. TSH assessment is crucial as hyperthyroidism is a common reversible cause of atrial fibrillation, as noted in the 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation 1. Troponin measurement helps rule out myocardial infarction, which can both cause and result from atrial fibrillation. BNP helps assess for heart failure, which frequently coexists with atrial fibrillation. Coagulation studies are important if anticoagulation therapy is being considered.
Some key points to consider when evaluating new onset atrial fibrillation include:
- The presence and nature of symptoms associated with AF
- The clinical type of AF (paroxysmal, persistent, or permanent)
- The onset of the first symptomatic attack or date of discovery of AF
- The frequency, duration, precipitating factors, and modes of termination of AF
- The response to any pharmacological agents that have been administered
- The presence of any underlying heart disease or other reversible conditions (e.g., hyperthyroidism or alcohol consumption), as outlined in the 2006 ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation 1.
Additionally, a toxicology screen may be appropriate if substance use is suspected, and an arterial blood gas can be useful if hypoxemia is a concern. These tests collectively help identify underlying causes, assess for complications, and guide both immediate management and long-term treatment decisions for patients with new onset atrial fibrillation. It's also important to note that echocardiography should be performed to assess LA and LV dimensions, LV wall thickness, and function, and to exclude occult valvular or pericardial disease, as recommended in the 2001 ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation 1.
From the Research
Initial Evaluation of New-Onset Atrial Fibrillation in the ED
The initial evaluation of new-onset atrial fibrillation in the emergency department (ED) should include several key laboratory tests to guide management and treatment.
- Transthoracic echocardiography to assess cardiac structure and function 2
- Serum electrolyte levels to evaluate for potential electrolyte imbalances that may contribute to atrial fibrillation 2
- Complete blood count to assess for anemia or other hematologic abnormalities 2
- Thyroid, kidney, and liver function tests to evaluate for underlying conditions that may contribute to atrial fibrillation 2
Additional Considerations
In addition to these laboratory tests, the CHA2DS2-VASc score should be used to assess stroke risk in patients with atrial fibrillation 2.
- Hemodynamically unstable patients, including those with decompensated heart failure, should be evaluated and treated emergently 2
- Most hemodynamically stable patients should be treated initially with rate control and anticoagulation 2
- Rhythm control, using medications or procedures, should be considered in patients with hemodynamic instability or in some patients based on risk factors and shared decision-making 2
Predictive Factors for Early Successful Cardioversion
Several predictive factors have been identified for early successful cardioversion in patients with new-onset atrial fibrillation, including: