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Atrial fibrillation is characterised by sometimes rapid, chaotic electrical activity in the upper chambers (atria) of the heart.
On this page: The heart's electrical system · Disturbed electrical impulses · Signs and symptoms · Causes · Tests · Treatment and management
The heart's electrical system
The heart normally beats at a regular rate of between 60 and 80 beats per minute.
The sino-atrial node, in the right upper chamber of the heart, is the primary pacemaker. It controls the initiation and conduction of the electrical impulse. This activates the heart's pumping action.
Disturbed electrical impulses
In atrial fibrillation (also known as AF and A Fib), instead of firing from the sino-atrial node, a number of impulses fire in different areas of upper chambers (atria). This causes individual muscle fibres to contract or fibrillate.
The upper chambers (atria) contract so rapidly that the lower chambers (ventricles) only respond to those impulses that are transmitted to the intermediate node (the atria-ventricular node, between the upper and lower chambers).
Fibrillation of the atria also decreases the amount of time the ventricles have to fill with blood. So the heart does not pump with the same efficiency. This reduces its output (the volume of blood pumped out of the heart to provide oxygen to the body).
Signs and symptoms
- Irregular heart rate (pulse).
- Dizziness.
- Shortness of breath.
- Occasionally chest pain.
Causes
Most people with atrial fibrillation have an underlying heart condition, such as coronary heart disease, heart attack (myocardial infarction), rheumatic heart disease, hypertension (high blood pressure), heart failure, cardiomyopathy, valve disease. It can also be caused by heart surgery.
Other causes:
- hyperthyroidism (over-active thyroid gland)
- infection – particularly of the lungs
- in a healthy person, excessive use of coffee, alcohol, or cigarettes.
Tests
Treatment and management
- Medication to control the heart's rhythm.
- Cardioversion (an electric current is used to restore a normal heart rate)
- Occasionally insertion of a pacemaker may be advised.
- Warfarin (prevents clotting in the blood) may be recommended.
Consider reducing caffeine and alcohol intake. Stop smoking. Read more about smoking and how to quit.
Avoid over-exertion. Rest if you experience dizziness, shortness of breath or chest discomfort. Contact your doctor if symptoms persist.
All treatment is dependent on the cause, and the symptoms you are experiencing. Your doctor will discuss your condition with you and decide on the appropriate treatment.
This information was first published in You and Your Heart - an education booklet for patients, families and friends. © 2006 Northern Sydney Central Coast Area Health Service
