Atrial fibrillation

Atrial fibrillation (AF) is a condition that affects the heart, causing an irregular heart beat.

This is known as a heart rhythm disorder (arrhythmia). Normally, your heart beats at a rate of 60 to 100 beats per minute when you are at rest, and all of the heart chambers beat in unison. If you have AF, the electrical signals that control your heartbeat are abnormal.

These signals cause the upper chambers of your heart (the atria) to beat unevenly and very quickly. In fact, the atria beat so quickly that the lower heart chambers (the ventricles) can’t quite keep up, and your heart doesn’t beat in the usual, coordinated manner.

This results in an irregular and rapid heart rate, often ranging from 100 to 180 beats per minute.

(Khan Academy, 2014)

Atrial fibrillation can be:

  • Chronic – ongoing uneven and fast heartbeat
  • Paroxysmal – repeated bouts that usually last less than 48 hours
  • Acute – a one-off episode of AF that may be the result of a particular short-term problem such as alcohol intoxication.

It occurs when the electrical impulses controlling the heart rhythm become disorganised, so that the heart beats irregularly and too fast. When this happens, the heart cannot pump blood around the body as well as it needs to.

Atrial fibrillation is a common problem affecting approximately 35,000 people in NZ (1% of the population). The risk of developing AF increases with age, occurring in about 5% of people older than 65 years and about 10% of people older than 80 years. Many people do not know they have it, with approximately one-third of those with AF thought to be undiagnosed.

Other things that increase your risk of AF include:

  • heart disease or heart valve problems
  • long-standing high blood pressure
  • chronic lung disease
  • an overactive thyroid gland.

It is possible for otherwise healthy people to have AF – in fact up to one-third of people with AF have no obvious underlying cause; a condition known as lone atrial fibrillation.

Atrial fibrillation is often picked up when having a medical examination for something else.

Key points:

  1. If you notice your pulse seems irregular, see your doctor.
  2. Atrial fibrillation is common as we get older, so see your doctor for blood pressure and pulse checks.
  3. Learn about the signs and symptoms of atrial fibrillation so you can seek help early.
  4. Keep your heart healthy by eating healthy foods, keeping physically active and being smoke free.
  5. If you do have atrial fibrillation, take your medication carefully as this can reduce symptoms and prevent complications such as stroke.

What are the risks associated with AF?

People with AF have a higher risk of stroke. The risk ranges from less than 1% per year to about 20% per year, depending on your age and other medical conditions. People with AF are also at risk of developing heart failure so it is an important condition to treat to reduce these risks.

How does AF cause stroke?

Because the atria are contracting quickly and abnormally, they don’t pump blood through the heart properly. Blood can then pool in the heart and a blood clot may form. If the clot breaks loose and leaves the heart, it can travel via your blood vessels to other organs in your body. If a clot lodges in a blood vessel that supplies your brain and cuts off the blood supply, it causes a stroke.

Symptoms

If you have AF, you may experience palpitations (an awareness of your heart beating or pounding in your chest). Other symptoms include:

  • chest pain
  • dizziness
  • light-headedness
  • shortness of breath
  • fatigue.

Some people have no symptoms at all, and AF is only detected after a doctor (or another healthcare worker) notices that your pulse is irregular.

Is an irregular pulse always due to AF?

Occasional missed beats or extra beats between regular beats are very common and usually nothing to worry about, but best discussed with your doctor. AF on the other hand has no pattern to it at all and is continuously irregular.

Take a test

Quick guide from the British Heart Foundation:

  1. Put one of your hands out so you’re looking at your palm.
  2. Use the index/first finger and middle finger of your other hand and place the pads of these fingers on the inside of your wrist. You should place them at the base of your thumb near where the strap of a watch would sit.
  3. Press lightly and feel the pulse. If you can’t feel anything press slightly harder or move your fingers around until you feel your pulse.
  4. Once you’ve found your pulse, continue to feel it for about 20-30 seconds. Feel the rhythm of the pulse and check if it’s regular or irregular.

Listen to these examples from the British Heart Foundation

Diagnosis

AF is diagnosed using a simple, painless test called an electrocardiogram (ECG).

  • When you have an ECG, small patches connected to wires (electrodes) are placed on your chest to measure the electrical impulses given off by your heart.
  • These electrical impulses are recorded on a piece of paper called an ECG strip.
  • The abnormal pattern of electrical impulses seen in people with AF is easily detected by the ECG.

However, if you have paroxysmal (irregular bouts of) AF, your heartbeat may be normal at the time the ECG is recorded. To detect paroxysmal AF, you may need to have a Holter monitor test arranged.

  • A Holter monitor is a portable device that you wear under your clothes.
  • It continuously records your heart's electrical impulses for at least 24 hours.

Treatment

The treatment for atrial fibrillation varies from person to person depending on a number of factors, including the severity of your symptoms, the cause and duration of your atrial fibrillation, and whether you have any underlying health problems. However, in general, the main aims of treatment are to:

  • prevent blood clots, therefore lowering risk of stroke
  • control your heart rate to restore a normal heart rhythm.

Blood clot prevention

  • Preventing blood clots is one of the most important parts of treating AF, as blood clots can cause stokes.
  • You may be prescribed blood-thinning medicines to prevent blood clots. These medicines include warfarin, dabigatran, heparin, and aspirin.
  • If you are taking blood-thinning medicines you will need regular blood tests to check how the medicine is working.

Rate control

  • You may also be prescribed medicines to slow down the rate at which the ventricles are beating and help bring the heart rate to a normal level.
  • If you have had AF for some time, it may be best to use betablockers or calcium channel blockers to slow your heart rate, as this is better for the heart.
  • Medicines used to control the heart rate include beta blockers (for example, metoprolol and atenolol), calcium channel blockers (diltiazem and verapamil), and digitalis (digoxin). Several other medicines are also available.

Rhythm control

If you are not doing so well on rate control medications, or have only recently started having AF, your doctor may prescribe medicines or recommend procedures to control the heart's rhythm.

Medicines for rhythm control

Medicines used to control the heart rhythm include amiodarone, sotalol, flecainide, propafenone, dofetilide, and ibutilide. Several other medicines also are available.

  • Electrical cardioversion is sometimes recommended to treat fast or irregular heartbeat. It involves the use of low-energy electrical shocks to trigger your heart into a normal rhythm. It is performed under a general anaesthetic.
  • Catheter ablation is a more invasive method that may be used to restore a normal heart rhythm. In this procedure, a catheter (a long, thin tube) is inserted a vein in the leg or arm and threaded all the way to the heart. Radio wave energy is used to damage the small portion of tissue responsible for the abnormal electrical signals.
  • Pacemakers help maintain a normal heart rhythm. They are used for people with AF that has not been effectively treated with less invasive treatments. Before inserting a pacemaker, catheter ablation is used to destroy the atrioventricular (AV) node in the heart. The AV node is a part of the electrical control system of the heart that coordinates the atrial and ventricular chambers. The pacemaker takes over the AV nodes role of maintaining a normal heart rhythm.
  • Heart surgery is very rarely required. The most common operation performed is known as the maze procedure, where a number of small incisions are made in the atria (upper chambers) of the heart to create a pattern of scar tissue. The scar tissue (which does not carry electrical currents) prevents the abnormal electrical signals that cause atrial fibrillation from travelling through the heart and causing an abnormal heartbeat.

Learn more

Tests & Investigations for Heart Disease Heart Foundation (NZ)
Learn about heart disease: atrial fibrillation Cardio smart (USA)
Arrhythmias – Normal heart beat animation Watch, Learn, Live: Interactive Cardiovascular Library – American Heart Association
Atrial fibrillation – Conduction system of the heart Watch, Learn, Live: Interactive Cardiovascular Library – American Heart Association

References

  1. Atrial fibrillation  National Heart, Blood and Lung Institute, NHI, US.

Credits: Original article written Aug 2014. Latest update Aug 2016.