Atrial Fibrillation

one of the most commonly experienced palpitations


Atrial fibrillation (AF) is one of the commonest heart rhythm disturbances.

Whilst many patients may be aware of an uncomfortable and irregular beating of the heart, particularly when they are at rest or in bed at night, others may have no awareness of their heart beat at all. Indeed in many patients the abnormality is only picked up by chance at a routine medical, for employment purposes for example.

In AF the electrical activity in the atria becomes chaotic with electrical discharges occuring spontaneously throughout the muscle causing an 'electrical storm' of activity that is continuously stimulating the A-V node which conducts the electricty as and when it can. This leads to the pulse becoming irregular and usually (although not always) faster.

Although a diagnosis of AF may seem very likely from a description of a patient's symptoms and examining the pulse it can only be definitively confirmed by conducting an electrocardiogram (ECG).

A particular difficulty may be in diagnosing asymptomatic, paroxysmal AF as the patient will not be aware of the rhythm disturbance and physical examination and the ECG will be normal inbetween attacks. If this is suspected prolonged and repeated continuous ECG recordings may be required using an ambulatory ECG machine (Holter monitor). Holter Monitor

An ECG showing Atrial Fibrillation

You can see from the ECG above that the beats look the same as those of the normal ECG except in two respects: they do not have any p-waves and they occur at irregular spacings.

Below is a diagram of the heart with the various structures labelled.

The second diagram shows an animation of the electrical activity in the heart when the heart is in Atrial Fibrillation. It can be seen that multiple areas in the atria are electrical active and discharge spontaneously and irregularly. The AV node is activated in an irregular fashion, but thereafter the electricity flows through the His-Purkinje system and into the ventricles normally.

  • PA pulmonary artery
  • SVC superior vena cava
  • IVC inferior vena cava
  • RA right atrium
  • LA left atrium
  • RV right ventricle
  • LV left ventricle
  • S-A sino-atrial node
  • A-V atrio-ventricular node