Arrhythmias
Atrial fibrillation
What is atrial fibrillation?
Heart contractions: Atrial fibrillation vs normal
Atrial fibrillation, or AFib as it is generally known, is the most common type of arrhythmia. It is estimated that, by the age of 80, more than 15% of Americans either have, or have had, AFib.
If you have AFib, the two upper chambers of your heart (the atria) contract very rapidly and irregularly, either all the time or sometimes.
A normal resting heart rate is 60 – 100 beats per minute, but fibrillating atria can beat 300 times or more per minute. When they are fibrillating, the atria are quivering rather than squeezing, and they don’t empty properly.
Most of the atrial impulses are blocked before they reach the ventricles, so the ventricles, which do the heart’s real pumping work, don’t beat as rapidly as the atria, but the resting heart rate of a person with AFib may still rise to 140 – 200 beats per minute.
Even though a pulse rate of 200 beats per minute sounds alarming, many people with AFib don’t know that they have it, especially if their hearts are only fibrillating occasionally, not all the time.
Symptoms of AFib, when they do occur, include dizziness and weakness, and people also describe a feeling of having a racing, fluttering heart (palpitations).
AFib can cause serious health problems if left untreated. It can damage your heart and lead to heart failure, especially left heart failure, and, importantly, it can raise your risk of having a stroke.
Stroke is a worry because the fast, shallow atrial contractions allow blood to pool in the atria instead of completely emptying into the ventricles. This pooled blood can then clot, and if a blood clot breaks off and travels to your brain it can cause a stroke.
If you want to learn more about a normal heartbeat and how your heart pumps take a look at our Your heart: The basics.
Blood clot forming in a fibrillating atrium
What causes atrial fibrillation?
The pumping mechanism of your heart is regulated by complex electrical signals.
These signals control your heart’s rate and rhythm, and are, in turn, controlled by the heart’s sinoatrial (SA) node, which is in the right atrium.
With each heartbeat, the SA node fires an electrical pulse that spreads down through the heart to the atrioventricular (AV) node. The AV node then passes the signal on to the ventricles and this causes your heart to beat in an organized way.
Electrical signals: Atrial fibrillation vs normal
In AFib, the SA node is no longer in full control and the electrical signals fire rapidly and chaotically – often more than 300 times per minute – from lots of different places in the atria.
The AV node blocks some of these signals, so the ventricles, which do the heart’s real pumping work, will typically contract only 140 – 200 times per minute, but the heart’s upper and lower chambers can no longer coordinate properly and the result is a fast and very irregular heartbeat.
Usually, AFib is the result of some kind of heart damage or structural problem, which can have a wide range of causes, from heart failure to infections. Anything that enlarges or distorts the left atrium can result in AFib.
Common causes of AFib include:
- Heart failure, particularly left heart failure
- Inflammations like pericarditis
- Serious left-sided heart valve disorders, such as mitral valve stenosis, mitral valve regurgitation, aortic valve stenosis, or aortic valve regurgitation
- Thyroid disease
- Hypertension
- Sleep apnea
- Heart damage as a result of stress, stimulant drugs, acute alcohol intoxication, or normal aging
If you want to learn more about how your heart works, take a look at our Your heart’s electrical system.
What are the symptoms of atrial fibrillation?
Some people with AFib have no symptoms and may not know that anything is wrong.
When symptoms do occur, they can vary from person to person, but they usually include palpitations, tiredness, and shortness of breath.
Here’s a list of common symptoms of AFib:
- A fluttering feeling in the chest (palpitations)
- A racing and/or irregular heartbeat
- Shortness of breath
- Dizziness
- Chest discomfort
- Extreme tiredness
How is atrial fibrillation treated?
Your doctor will determine the best course of treatment for your AFib depending on its severity and the potential impact on your health.
First, you will probably be prescribed medications that will slow and control your heart rate, such as beta blockers and calcium channel blockers, or a drug with anti-arrhythmic properties.
Then, if you are at risk of having a stroke (especially if you have other disorders that raise that risk), you will also be prescribed a blood-thinning medication to prevent clots.
If necessary, your doctor may recommend resetting your heart’s rhythm using cardioversion, which involves delivering a small shock to your chest, or a catheter-based procedure called cardiac ablation, which involves deactivating the damaged tissue that is disrupting your heart’s normal electrical signaling.
Treatments for AFib include:
- Medications to control your heart rate
- Blood-thinning medication to prevent clots and strokes
- Cardioversion (a small shock to the chest that resets the heart’s rhythm)
- Medications that help to maintain your heart’s normal rhythm
- A catheter-based procedure called cardiac ablation (if medications and cardioversion don’t help)
- Avoiding stimulants like caffeine and decongestants
- Maintaining a healthy lifestyle to help control blood pressure, body weight, and stress levels
What are the aims of treatment?
The immediate aims of treatment for AFib are to reset the rhythm of your heart and slow and control your heart rate.
The ultimate aim is to prevent damage to your heart, which can lead to heart failure, and lower your risk of having a stroke or heart attack.