Investigations

The principle investigation of choice is the ECG.

• should be done in all patients whether symptomatic or not, in whom AF is suspected because an irregular pulse has been detected (1)
  • perform a 12-lead electrocardiogram (ECG) to make a diagnosis of atrial fibrillation if an irregular pulse is detected in people with suspected atrial fibrillation with or without symptoms (2)
    
    
• if paroxysmal AF is suspected and is undetected by standard ECG recording,
  • a 24-hour ambulatory ECG monitor should be used in suspected asymptomatic episodes or symptomatic episodes less than 24 hours apart
  • use an ambulatory ECG monitor, event recorder or other ECG technology for a period appropriate to detect atrial fibrillation if symptomatic episodes are more than 24 hours apart (2)

Other investigations include:

• full blood count
• urea and electrolytes
• thyroid function tests
• chest X-ray - to identify lung diseases if suggested by clinical findings (3)
• echocardiography:
  • size of left atrium
  • left ventricular function
  • transoesophageal echocardiography is more sensitive for the detection of thrombus

Reference:

• (1) Lafuente-Lafuente C, Mahé I, Extramiana F.Management of atrial fibrillation. BMJ. 2009;339:b5216.
• (2) NICE (April 2021). Atrial fibrillation: diagnosis and management.
• (2) NICE (2006). Atrial fibrillation.