Some people with atrial fibrillation, particularly older people, do not have any symptoms. The irregularity in heart rhythm is often only discovered during routine tests or investigations for another condition.

Typically, a cardioversion (where the heart is given a controlled electric shock to restore normal rhythm) is carried out. At this point, many people feel much better and realise they had not been feeling normal.

People often attribute tiredness and feeling lethargic to ageing, but once normal rhythm is restored, they realise these symptoms were caused by atrial fibrillation.

Heart palpitations

The most obvious symptom of atrial fibrillation is heart palpitations – where the heart feels like it's pounding, fluttering or beating irregularly, often for a few seconds or possibly a few minutes.

As well as an irregular heartbeat, your heart may also beat very fast (often considerably higher than 100 beats per minute). You can work our your heart rate by checking your pulse in your neck or wrist. Other symptoms you may experience if you have atrial fibrillation include:

• tiredness and being less able to exercise
• breathlessness
• feeling faint or lightheaded
• chest pain

The way the heart beats in atrial fibrillation reduces the heart's performance and efficiency. An electrocardiogram (ECG) can be used to confirm a diagnosis of atrial fibrillation. An ECG is a test that records the rhythm and electrical activity of your heart.

Causes

The exact cause of atrial fibrillation is unknown, but it's more common with age and affects certain groups of people more than others. Atrial fibrillation is common in people with other heart conditions, such as:

• high blood pressure (hypertension)
• atherosclerosis
• heart valve disease
• congenital heart disease
• cardiomyopathy
• pericarditis

It's also associated with other medical conditions, including:

• an overactive thyroid gland
• pneumonia
• asthma
• chronic obstructive pulmonary disease (COPD)
• lung cancer
• type 2 diabetes
• pulmonary embolism
• carbon monoxide poisoning

But not everyone with atrial fibrillation has one of the conditions above. It can sometimes affect people who are physically very fit, such as athletes. When no other conditions are associated with atrial fibrillation, it's known as lone atrial fibrillation.

Triggers

Certain situations can trigger an episode of atrial fibrillation, including:

• drinking excessive amounts of alcohol, particularly binge drinking
• being overweight
• drinking lots of caffeine, such as tea, coffee or energy drinks
• taking illegal drugs, particularly amphetamines or cocaine
• smoking