Florida Hospital Cardiovascular Institute

What is Atrial Fibrillation?

Atrial fibrillation (A-Fib) occurs when the upper chambers of the heart beat irregularly or are not properly synchronized with the lower chambers. Often, the only sign of atrial fibrillation is a fluttering sensation or palpitations in your chest.

When atrial fibrillation occurs, the electrical connection between the atria (the upper chambers) and the ventricles (the lower chambers) is overloaded. The result is a faster than normal heart rate. Where a normal range is 60 to 100 beats a minute, atrial fibrillation may cause the heart to beat at 100 to 175 times a minute.

In most cases, atrial fibrillation isn’t life threatening and will subside on its own. But it can lead to complications, including the formation of blood clots, which, if they become lodged in the artery in the brain, can cause a stroke.

Causes of Atrial Fibrillation

Episodes of atrial fibrillation aren’t unusual, particularly as you get older. In fact, three to five percent of all adults over 65 have atrial fibrillation.

To effectively move blood through your body, your heart muscle acts like a pump. It contracts and relaxes in a rhythmic fashion. Keeping the rhythm steady is the responsibility of a group of cells in the upper right chamber of your heart called the sinus node. Your natural pacemaker, known as the “sinus node”, sends the signals that tell your heart to beat. The signal first tells the upper chamber to pump blood to the lower chamber. Then it tells the lower chamber to contract and pump the blood through the body.

Atrial fibrillation happens when there are abnormalities in the heart or when the heart has been damaged. Just a few of the causes include:

• Heart attacks
• Abnormal heart valves
• Congenital heart defects
• High blood pressure
• A metabolic imbalance, such as an overactive thyroid
• Use of stimulants such as medications, caffeine, alcohol or tobacco
• Emphysema or other lung diseases
• Previous heart surgery
• Viral infections
• Stress due to pneumonia, surgery or other illnesses
• Sleep apnea

Symptoms

In many cases you can have atrial fibrillation without knowing it. Episodes can be fairly brief, mild or go unnoticed until you visit your doctor for a routine examination.

If you do have symptoms, they can include:

• Palpitations (the feeling that your heart is fluttering, racing or beating irregularly)
• Weakness
• Feeling lightheaded
• Confusion
• Experience shortness of breath
• Mild chest pain

Risk Factors

There are many risk factors associated with atrial fibrillation. Some of these risk factors can be controlled while others cannot.

For instance, you can stop smoking, lose weight or take medications to control your blood pressure. But you can’t do anything to change your family history, your gender or your age.

Of course, the more risk factors you have, the greater the chance the risk you’ll experience atrial fibrillation and developing heart disease.

Following are risk factors you can do something about:

• High cholesterol
• High blood pressure
• Diabetes
• Excess weight
• A diet high in fat
• Excess weight
• Smoking
• Alcohol abuse
• Drug abuse
• Sedentary lifestyle
• Stress
• Taking decongestants or diet and herbal supplements

There are some risk factors you just can’t do anything about. But knowing that they exist and knowing how they can affect your predisposition toward heart disease can help you manage atrial fibrillation.

There are some risk factors you just can’t do anything about. But knowing that they exist and knowing how they can affect your predisposition toward heart disease can help you manage atrial fibrillation.

• A history of heart disease in the family
• Congenital heart disorders
• Growing older
• Gender (males are at greater risk statistically)

Evaluation and Diagnosis

Your physician will usually begin with an in-depth medical history, followed by a physical exam, an electrocardiogram (ECG) and an echocardiogram.

Your medical history may give your doctor the first indications of atrial fibrillation. This includes a history of heart problems, a report of chest pains or shortness of breath, sudden weight loss or feeling hot all the time.

During the physical exam, your doctor may check to see if your heart is enlarged, listen for heart murmurs or fluid in the lungs, feel your thyroid glands or even test your reflexes. Each phase of the exam can help your doctor pinpoint the cause of the atrial fibrillation.

The most effective tool for diagnosing atrial fibrillation is the electrocardiogram. In a normal heart, the sinus rhythm is a series of bumps and lines that show the contractions of the atria and ventricles. When atrial fibrillation is present, the bumps in the ECG are replaced by irregular lines.

Finally, your doctor may suggest you undergo an echocardiogram, where sound waves are translated into images of the heart. This imaging can show if your atria is enlarged or if there is an impairment in the pumping function of the left ventricle.

Depending on the results of these tests, your doctor may opt to run additional tests, including a thyroid-stimulating hormone (TSH) test to identify an overactive thyroid or perform imaging on the legs or lungs to identify potential blood clots. Blood tests or heart monitors may also be integrated into the testing to help in the diagnosis.

Types of Atrial Fibrillation

There are two major types of atrial fibrillation, primary and chronic.

• Primary (Lone) Atrial Fibrillation: Usually seen in people between the ages of 30 and 60 years of age, its root cause usually can’t be identified.
• Chronic Atrial Fibrillation: When the condition is associated with an existing heart issue, it’s known as chronic atrial fibrillation. Even with treatment, it may not go away or go away permanently.

For each form of atrial fibrillation, there are narrower classifications. These are determined by the length of the episodes and how often they occur. You may hear your doctor refer to your type of atrial fibrillation as paroxysmal, persistent or permanent.

• Paroxysmal Atrial Fibrillation: When atrial fibrillation occurs unpredictably, it is referred to as paroxysmal. The episodes can occur a few times a year or even every day. The heart returns to its natural rhythm on its own. Approximately 25% of people with paroxysmal atrial fibrillation will develop the permanent form.
• Persistent Atrial Fibrillation: If an episode lasts longer than 48 hours and won’t return to normal without treatment, it is known as persistent atrial fibrillation.
• Permanent Atrial Fibrillation: This type of atrial fibrillation occurs when the irregular rhythm continues indefinitely and can’t be corrected with treatment.