• Atrial fibrillation (AF) is a common disorder affecting the heart's rhythm. In AF the two upper chambers of the heart - the atria - beat at an abnormally fast rate.
• AF can cause general feelings of tiredness, weakness, reduced ability to exercise, discomfort or dizziness. Occasionally this may lead to fainting or collapse.
• However, the symptoms of AF are not always obvious. Up to 1 in 5 people with AF are undiagnosed, and therefore not treated.