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Atrial Fibrillation 
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Atrial Fibrillation
The normal heart rate for an adult is between 60 and 100 beats every minute. When the heart is in AF, the atria can beat over 300 times every minute.
AF itself is not life-threatening. If left untreated, the side effects of AF can be life-threatening. AF makes it harder for the atrial to pump blood to the ventricles (the lower chambers of the heart). With the blood moving more slowly, it is more likely to form clots. If the clot is pumped out of the heart, it could travel to the brain and lead to a stroke. Without treatment, AF can also cause a fast pulse rate for long periods of time. This means that the ventricles are beating too fast. This can weaken the heart muscle over time, and lead to heart failure. AF is the most common type of arrhythmia. There are 2.3 million people in the United States that have AF. About 160,000 new cases are diagnosed every year. Eight out of every 100 people over the age of 65 are diagnosed with AF. Although it usually occurs in adults older than 60, younger adults can develop AF too.
What is Atrial Fibrillation?
The electrical system of the heart is the power source that makes the heart beat. Electrical impulses travel along a pathway in the heart and make the atria and the ventricles work together to pump blood through the heart.
A normal heartbeat begins as a single electrical impulse that comes from the SA node, a small bundle of tissue located in the right atrium. The impulse sends out an electrical pulse that causes both atria to contract (tighten) and move blood into the lower ventricles. The electrical current then passes through a small bundle of tissue called the AV node (the electrical bridge between the upper and lower chambers of the heart), causing the ventricles to squeeze and release in a steady, rhythmic sequence. As the chambers squeeze and release they draw blood into the heart and push it back out to the rest of the body. This is what causes the pulse we feel on our wrist or neck.
AF occurs when the electrical impulse does not follow this order. Instead of one impulse moving through the heart, many impulses begin in the atria and fight to get through the AV node. There are two main factors that allow this abnormal electrical rhythm to occur and continue. First, the structure of the heart chambers and the electrical pathway through the heart may change. This happens more often as we get older. Second, as the electrical pathway changes, one or more “triggers” may develop. “Triggers” are electrical circuits that send extra impulses at a faster than usual rate. These extra impulses are all trying to get through the AV node and the atria begin to fibrillate, or twitch, in a fast and disorganized way.
Three Types of AF
- Paroxysmal AF – Paroxysmal AF refers to AF that occurs sometimes and then stops. The AF stops by itself and the heart returns to normal rhythm. The AF may last for seconds, minutes, hours or days before the heart returns to its normal rhythm. People with this type of AF usually have more symptoms than others. As the heart goes in and out of AF, the pulse rate may change from slow to fast and back again in short periods of time.
- Persistent AF – Persistent AF is when the AF does not stop by itself. Medications or a special type of electrical shock (called a cardioversion) is used to help the heart return to normal rhythm. If no treatment is given, the heart will stay out of rhythm.
- Permanent AF – Permanent AF is when the AF cannot be fixed. Medications and controlled electrical shock cannot help return the heart to normal rhythm.
Risk Factors for Atrial Fibrillation
Some people who are living healthy lives and have no other medical problems do develop AF. In most cases, though, we do know the cause. The most common causes and risk factors include:
- Older than 60 years of age
- Diabetes
- High blood pressure
- Coronary artery disease
- Prior heart attacks
- Congestive heart failure
- Structural heart disease (valve problems or congenital defects)
- Prior open heart surgery
- Untreated atrial flutter (another type of abnormal heart rhythm)
- Thyroid disease
- Chronic lung disease
- Sleep apnea
- Excessive alcohol or stimulant user
- Serious illness or infection
Symptoms of Atrial Fibrillation
The symptoms of AF are different for each person. Many people feel no symptoms at all. They do not know they have AF or that there is a problem, while others can tell as soon as it happens. This is because the symptoms depend on age, the cause of the AT (heart problems, other diseases, etc.) and on how much AF affects the pumping of the heart.
The symptoms of AF include:
- Feeling over-tired or a lack of energy (most common)
- Pulse that is faster than normal or changing between fast and slow
- Shortness of breath
- Heart palpitations (feeling like your heart is racing, pounding or fluttering)
- Trouble with everyday exercises or activities
- Pain, pressure, tightness or discomfort in your chest
- Dizziness, lightheadedness or fainting
- Increased urination (using the bathroom more often)
Complications from Atrial Fibrillation
AF is usually not life threatening. However, AF makes the atria contract, or tighten, much faster than normal and in a disorganized way. This makes it harder for the atria to pump blood to the ventricles. With the blood moving more slowly, it is more likely to form clots. If the clot is pumped out of the heart, it could travel to the brain and lead to a stroke. This is the cause of about 15 out of every 100 strokes. Click the link to find an animation on stroke.
In addition, AF can also cause a fast pulse rate for long periods of time. This means that the ventricles are beating too fast. When the ventricles beat too fast for long periods of time, the heart muscle can become weak. This condition is called cardiomyopathy. This can lead to heart failure and long-term disability.
To help prevent these complications, treatment for AF usually includes one medication to reduce the chance of blood clots and stroke, and another to keep the pulse from going too fast.
How is Atrial Fibrillation Diagnosed?
There are There are several tests that can be done to check for a fast or irregular heartbeat. Your doctor may order these tests if you are having signs or symptoms of a heart problem. The symptoms include heart palpitations (feeling like your heart is racing, pounding or fluttering), shortness of breath or dizziness.
- Electrocardiogram (ECG) – An ECG is a snapshot of your heart’s electrical activity. Stickers (electrodes) are attached to your chest, arms and legs. These electrodes measure the rate and rhythm of your heart.
- Holter monitor – A Holter monitor is a portable ECG. It can be worn for several days. Stickers (electrodes) are placed on your chest and are then connected to a small recording machine that is usually worn around the waist. It records the electrical activity of your heart for your doctor to review later. Click the link for a demonstration of a holter monitor.
- Mobile cardiac monitoring - A mobile cardiac monitor is worn for up to 30 days. It records your heart’s beat when it is in normal and abnormal rhythm. The results are automatically sent to your physician. Your physician uses this information to evaluate your symptoms and determine what is causing the arrhythmia.
- Event monitor – An event monitor is a portable ECG that is used for patients who have an irregular heart rhythm every once in a while. You will carry the monitor with you at all times and attach it to your chest when you feel symptoms. This lets your doctor check your heart rhythm at the time of your symptoms.
- Echocardiogram – An echocardiogram uses sound waves to produce images of your heart. This test allows your doctor to see how your heart muscle is moving and pumping blood. You may have one of several types of echocardiograms. Learn more about how an echocardiogram works.
- Transthoracic echocardiogram (TEE) – This is a standard non-invasive (no incisions or cuts) echocardiogram that gives your doctor a picture of your beating heart. A technician spreads a special gel on your chest and then uses an imaging device, called a transducer, that gives off and reads sound waves. The imaging device records the sound waves bouncing off the walls and valves (echoes) in your heart. A computer then creates a video of your heart. This video can show the size of your heart, how well your heart is working, if the heart valves are working and if there are blood clots in your heart.
- Transesophageal echocardiogram – A transesophageal echocardiogram, or a TEE, is often done when the doctor needs to get a good picture of the back of your heart. To get a clear picture, a probe called a transducer is placed down your esophagus (the tube that connects your mouth to your stomach). The esophagus passes right behind the heart. This procedure can be uncomfortable. You will be given a small amount of sedation through an intravenous (IV) line and your throat will be sprayed with anesthesia to make the area numb. Once the probe is in place, it works the same way as described above.
- Cardiac computerized tomography (CT) or magnetic resonance imaging (MRI) – Cardiac computed tomography, or cardiac CT, uses an X-ray machine and a computer to take clear, detailed pictures of the heart. During a cardiac CT scan you will lie on a table. An X-ray machine will move around your body. The machine will take pictures of your heart and chest. A computer will put the pictures together to make a three-dimensional (3D) picture of your heart and chest.
- A cardiac MRI uses radio waves, magnets and a computer to create pictures of your heart. During a cardiac MRI you will lie on a table inside a long tube-like machine. Cardiac MRI creates detailed pictures of your heart as it is beating. The MRI will create snapshots as well as videos. Doctors use cardiac MRI to see the beating heart, the parts of the heart and how the heart is working.
