Manchester United manager Sir Alex Ferguson has been fitted with a pacemaker after he was found to be suffering from a minor heart condition last year.
1: Sir Alex Ferguson's condition, supraventricular tachycardia, is a non-life threatening heart rhythm disturbance caused by rapid electrical activity in the upper heart (the atria)
2: The same condition can affect the lower heart (the ventricles) as ventricular tachycardia - usually a sign of underlying heart disease
We examine what he was diagnosed with, what may have caused it and what treatments are given.
What is Sir Alex's condition?
Sir Alex Ferguson was diagnosed with a condition called supraventricular tachycardia (SVT).
This is a disturbance of the heart rhythm caused by rapid electrical activity in the upper parts of the heart - the atria.
The heart goes from beating at a normal resting pulse of around 70 beats per minute to anywhere between 140 and 240 beats per minute.
Patients usually experience this surge as palpitations - a fluttering of the heart - but they may also feel dizzy or faint.
Experts say the condition is uncomfortable but not harmful.
Is the condition caused by stress?
It is possible that SVT can be triggered by stress - although there are other potential triggers, such as being rundown because of a cold or flu or drinking too much caffeine.
However, the underlying cause is likely to be a slight congenital abnormality of the electrical activity of a person's heart.
This can lie dormant and not affect people for decades.
Professor Sir Charles George, medical director of the British Heart Foundation, told the BBC: "People tend to associate these rhythm disorders with periods of anxiety.
"But in most people, there's no obvious immediate cause."
Although people can suffer repeated attacks of SVT, many only have one episode in their lives.
How common is SVT?
Experts say it is a fairly common heart rhythm disorder.
Thousands of people in the UK will have suffered SVT.
What medical treatment has Sir Alex received?
After his condition was revealed during a routine check-up last year, doctors will have carried out an electrocardiogram (ECG) to test the rhythm and activity of the heart and checked to ensure he was not suffering from any other cardiac conditions.
Once SVT is diagnosed, the aim is to return the heart back to its normal rhythm.
It is understood that in Sir Alex's case, this was done using a treatment called cardio version where, under anaesthetic, a mild electrical charge is carefully applied to switch the heart beat back to normal.
Patients are then kept in hospital for observation for a few hours to check the procedure has been successful.
Sir Alex has now been fitted with a pacemaker.