Video: Atrial fibrillation
What is atrial fibrillation?
Atrial fibrillation is an irregularity in the heart’s rhythm (arrhythmia). During atrial fibrillation, the heart beats abnormally and often fast. It can lead to heart failure, stroke and death.
Atrial fibrillation affects approximately 240,000 people in Australia. It is especially common in people over 75 years.1
The heart consists of four chambers, two upper (atria) and two lower (ventricles). Inside the upper right chamber (right atrium) is the heart’s natural pacemaker, the sinus node. The sinus node normally produces rhythmic contractions of heart muscle using regular electrical impulses. These travel through the atrium and are transmitted to the ventricles by the atrioventricular (AV) node.
However, during atrial fibrillation, the sinus node is overwhelmed by random electrical discharges from other areas within the atria. This irregular electrical activity spreads through both atria, causing the muscles of the atria to quiver or ‘fibrillate’. This irregular electrical activity occurs at a very fast rate – about 300 beats per minute. The AV node filters a variable number of these impulses, resulting in the ventricles beating irregularly at a normal or rapid rate.
Atrial fibrillation can sometimes occur within a normal heart and there are inherited genetic factors that can cause atrial fibrillation. However, more commonly there are other medical conditions that contribute to the development of this condition. These may include:
- High blood pressure (hypertension);
- Heart attack;
- Heart defect at birth;
- Endocrine disorders (e.g., hyperthyroidism and phaeochromocytoma);
- Heart surgery, and;
- Viral infections.
Healthy and atrial fibrillation (irregular) heartbeat traces.
Risk factors of atrial fibrillation may include:
- Older age;
- Drug use;
- Alcohol use;
- Caffeine, and;
- A family history of atrial fibrilation.
Depending on your condition, atrial fibrillation is classified as one of three types.
This is the first detection of irregular beating of the heart of less than 24 hours' duration, also known as a ‘one-off'.
Recurrent atrial fibrillation
Recurrent atrial fibrillation is characterised by more than two episodes of irregular beating and may be sub-classified into:
- Paroxysmal (the heart stops fibrillating itself, usually in less than 24 hours);
- Persistent (the heart beats irregularly for longer than seven days), and;
- Permanent (continuous or ongoing condition in which the heart beats irregularly all the time).
Post-operative atrial fibrillation
Post-operative atrial fibrillation occurs in about one in four people who have had heart surgery.1 There is evidence suggesting that pre-treatment with medications such as beta-blockers, sotalol, amiodarone and statins can reduce the incidence.
Signs and symptoms
Atrial fibrillation often has no obvious symptoms, so it may remain undetected for extended periods of time. If signs and symptoms of atrial fibrillation do occur, they may include:
- Fast and abnormal heartbeat;
- Irregular heartbeat;
- ‘Fluttering’ of the heart;
- Chest pains;
- Dizziness, and;
- Fainting spells.
Methods for diagnosis
Atrial fibrillation may be diagnosed by:
During an electrocardiogram, electrodes are attached to your chest while you lie down. These record your heart’s electrical activity from different angles. This test is used to determine if there are any abnormalities in your heart’s rhythm. To see how your heart responds to stress, an electrocardiogram can be performed while you jog on a treadmill.
An electrocardiogram procedure.
Echocardiography uses ultrasound waves to create an image of the heart. It allows your doctor to see the size of your heart and how well it is working, whether the heart valves are leaking and highlighting areas of damage. To determine how the heart is working under stress rather than resting conditions, an echocardiogram can be performed after exercise.
A Holter monitor is a device that is able to record the electrical activity and heart rate over time (e.g, 24 hours). It is worn under your clothing and stays attached while you sleep. This is used if atrial fibrillation is suspected but episodes do not last long enough to get to your doctor and be captured by an ECG.
This device is similar to a Holter monitor, but only transmits signals when you are experiencing symptoms. An event recorder may be worn for up to a month and is useful in diagnosing rhythm disturbances that occur at unpredictable times.
A chest X-ray gives an indication of the condition of your heart and lungs. It may also help to identify issues other than atrial fibrillation to explain your signs and symptoms.
Types of treatment
Treatment for atrial fibrillation varies, depending on the severity of your condition. Some treatments include:
Medication to restore the rhythm of the heart can include digoxin, amiodarone and other ‘anti-arrhythmic’ agents. To slow the heart, beta-blockers may also be used. Some medications may cause unwanted toxicity, so you might need regular tests to check your kidney, thyroid and liver function.
Atrial fibrillation may lead to some people having a stroke. To reduce the risk of this, some blood-thinning medications are regularly prescribed to lessen the chance of blood clots developing in the heart. The most common medication used to prevent blood clots has previously been warfarin, which requires regular blood tests to monitor its effects. However, newer agents such as dabigatran that do not require such monitoring are becoming increasingly common. If you are at high risk of bleeding, your doctor may advise you to take aspirin or clopidogrel.
Electrical cardioversion is a technique that uses electric shock therapy to restore the heart’s rhythm. While you are under sedation, your heart’s electrical system can be reset by an electric shock to your chest. To help the heart beat normally after the treatment, medication may be needed over the longer term.
If you have not responded to less invasive treatments, including medication or electrical conversion, sometimes surgical treatment may be recommended. These procedures are usually only performed if there is also another reason to intervene, such as needing surgery on heart valves. Some treatment options include:
This method aims to destroy the small section of the heart tissue that is causing atrial fibrillation. To perform this procedure, a small opening is made in the upper thigh or groin. A catheter is then inserted into the blood vessel and moved along until it reaches the heart. Upon reaching the heart, an electrode at the end of the catheter is activated. Radio waves then destroy the small area of the heart responsible for the atrial fibrillation.
A maze operation is used to ‘trap’ the source of atrial fibrillation using a similar procedure to catheter ablation. This technique creates small scars to localise the site causing atrial fibrillation. This can help to allow the heart’s regular node (sinus node) to take control.
During recurrent atrial fibrillation, blood may pool, become stagnant and form a clot. A stroke occurs when the blood clot breaks free from the atria to block an artery in the brain. Patients with more persistent forms of atrial fibrillation are more prone to experiencing a stroke, particularly those over 65 years of age. If atrial fibrillation is left untreated, the risk of developing a stroke is quite high.
The irregular muscle contractions of atrial fibrillation are not efficient and can create a burden on your heart and circulation. This can occur quickly if the heart is beating very fast, or can happen more slowly, over years. If heart failure develops, you may feel tired and weak, or breathless when you are doing things.
There are some lifestyle changes that are may help you prevent or manage atrial fibrillation. These include: