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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


Last edited 05/2021 and last reviewed 05/2021