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Atrial fibrillation is common post-operative complication

When the heart is not beating at a steady rate (usually between 60 and 100 times a minute), the irregular heartbeats are called arrhythmias. The most common type of sustained arrhythmia is atrial fibrillation, affecting about two million Americans every year. Atrial fibrillation got its name because the atria (the heart's upper chambers) send rapidly firing electrical signals that cause them to quiver, rather than contract normally. The result is an abnormally fast and highly irregular heartbeat.

Atrial Fibrillation: An arrhythmia in which abnormal electrical impulses beginning in the heart's upper chambers (atria) cause rapid, irregular beats in the lower chambers (ventricles).

In AF, since the upper chambers of the heart quiver instead of contracting, blood may pool in the atria and there is a risk of blood clots being formed. If a blood clot breaks off into the general circulation, this could cause a stroke. As a result, atrial fibrillation causes approximately 15 percent of all strokes, and is associated with both greater complications and greater risk of death from heart attacks in people over the age of 65. The risk of stroke in atrial fibrillation can be reduced by taking anticoagulants (medications that inhibit blood clotting).

Atrial fibrillation is associated with many different underlying heart conditions, such as heart failure or valvular heart disease. Many patients also experience atrial fibrillation in the absence of structural heart disease (lone atrial fibrillation), due to causes such as abnormal thyroid function or excessive alcohol use. If necessary, cardioversion may be used to bring the heartbeat back to normal by using either drugs or defibrillator paddles that deliver an electric shock to the patient's chest. However, although cardioversion may restore a normal rhythm, there is a risk that atrial fibrillation may happen again. Therefore, antiarrhythmics may be required to maintain a normal rhythm. Surgery or ablation may also be options in some cases. With treatment, many people are able to live normal, active lives.

Atrial fibrillation (AF) is a rapid, irregular heart rhythm (arrhythmia) caused by abnormal electrical signals from the upper chambers of the heart (atria). Electrical signals should normally be coming only from the sinus node (the heart's natural pacemaker) in a steady rhythm — about 60 to 100 beats per minute. AF is marked by rapidly firing signals that come from the atria, increasing the heart rate to 100 to 175 beats per minute or more. In response to these many rapid and chaotic signals, the atria quiver instead of contracting properly. Due to these abnormal contractions, the heart's lower chambers ventricles beat rapidly and irregularly.

Conduction System: The heart has its own electric pacemaker, which regulates the heartbeat. Specialized nerves send signals to the pumping chambers, telling them to contract.

Since the atria are quivering and not contracting normally, blood may pool in the atria, which can lead to formation of blood clots. If part of a clot breaks off and leaves the heart via the arteries, it can become lodged in blood vessels leading to the brain, lungs or other parts of the body. Depending upon where the traveling blood clot (embolus) becomes lodged, the patient could experience symptoms ranging from cold feet to a stroke.

AF is the most common type of sustained arrhythmia, affecting two million people each year in the United States alone. However, not all irregular heartbeats are a sign of AF. Skips, pauses or unusually strong/irregular heartbeats palpitations commonly occur in people with no history of heart problems. Some are related to more serious cardiac problems, and others are not. People who experience irregular heartbeats are encouraged to speak with their physician.

Both atrial fibrillation and atrial flutter increase the risk of stroke. According to the American Heart Association, they lead to over 54,000 deaths in the United States each year. The risk of developing atrial fibrillation increases dramatically with age. As a result, approximately 70 percent of patients with atrial fibrillation are between the ages of 65 and 85 years old.

Many patients who experience AF are symptom-free and unaware of their abnormal rhythms. Other patients experience physical symptoms, including:

Palpitations (heartbeats that are rapid, pounding, forceful, uncomfortable or in some way obviously irregular)
Dizziness
Fainting (syncope)
Weakness
Fatigue
Shortness of breath (dyspnea)
Chest pain that may or may not be angina

Brief episodes of AF are known as transient atrial fibrillation. These episodes occur for a few minutes to a few hours at a time before the heart returns to a normal rhythm. Transient AF is harder to diagnose because it may or may not be detected by the patient. Chronic, constant cases of AF are easier to diagnose.

There are a variety of ways to diagnose AF. For example, the physician may use a stethoscope to listen for irregular heart rhythms. Additional tests that may be ordered include the following:

Electrocardiogram

EKG (electrocardiogram). An electrocardiogram (EKG) is a recording of the heart's electrical activity as a graph on a moving strip of paper or video monitor. The highly sensitive electrocardiograph machine helps detect heart irregularities, disease and damage by measuring the heart's rhythms and electrical impulses.
Holter monitor. A continuous EKG is temporarily attached to an ambulatory (freely moving) patient for a 24-hour period (though it can be used for up to five days). This test can detect or diagnose irregular heartbeats (arrhythmias), as well as oxygen deficiencies (cardiac ischemia). It can also help to evaluate the effectiveness of any medications, especially antiarrhythmics, that the patient may be taking.
Chest x-ray (roentgenography). A radiation-based image on film that offers the physician a picture of the general size, shape, and structure of the heart and lungs.
Blood tests. These tests measure blood oxygen levels, electrolytes, hormone levels and other possible indicators of an underlying cause of AF.
Stress test. An electrocardiogram is performed while the patient exercises in a controlled manner on a treadmill or stationary bicycle at varied speeds and elevations. The reaction of the heart under exertion can be measured and evaluated. It may be ordered to assess the extent of artery damage and/or coronary artery disease.
Echocardiogram of the heart and major arteries. This test uses sound waves to track the structure and function of the heart. A moving image of the patient's beating heart is played on a video screen, where a physician can study the heart's thickness, size and function. The image also shows the motion pattern and structure of the four heart valves, revealing any potential leakage (regurgitation). During this test, a Doppler ultrasound may be done to evaluate blood flow in the coronary arteries, the blood vessels of the arms and legs, and the carotid arteries in the neck.
Transesophageal echocardiography (TEE). This test uses a small transducer attached to an endoscope that is inserted through the patient's mouth and throat, and into the esophagus (the long tube from the throat to the stomach). This will not affect the patient's ability to breathe freely but might temporarily interfere with swallowing. Once positioned, the transducer can transmit a very clear image of the heart's size and function. It may be used to detect blood clots in the atria.
Electrophysiology study (EPS). A test that involves a number of electrode catheters that are fed through a blood vessel and into the atria and ventricles. Once in place, electrical activity is recorded to assess the presence and source of irregular heart rhythms, or to see if there has been any progress from medical treatments.

As with any arrhythmia, treatment of AF will depend on the nature and severity of the irregular rhythm, as well as the nature of any underlying heart condition(s). Treating AF usually includes treating the underlying condition, such as high blood pressure or heart failure.

Medications that may be used include the following:

Beta blockers, calcium channel blockers and Digoxin. Medications that slow transmission of electrical impulses from the atria to the ventricles. This slows the overall heart rate during atrial fibrillation.
Anticoagulants. Medications that inhibit the formation of blood clots.
Antiarrhythmics. Medications that stabilize the heart rhythm, helping to maintain a normal rhythm.

Prescribed medication (particularly anticoagulants and antiarrhythmics) must be monitored carefully to detect any side effects, which can include bleeding or increased/worsened arrhythmias. Patients on such medications are advised to become familiar with taking their own pulse, so that any irregular rhythm will be promptly discovered.

More invasive treatments include the following:

Cardioversion returns AF to a normal heart rhythm through either an electric shock or drugs. Cardioversion does not work for all patients. Only those who can maintain normal sinus rhythm are approved for this procedure. In those patients, cardioversion has about an 80 to 95 percent success rate.
Ablation, through the use of radiofrequency energy, may be able to burn out (ablate) the tissues and pathways from which the faulty signals arise. Because ablation may sometimes diminish the heart's natural pacemaking abilities, an artificial pacemaker may be implanted to keep the heart beating at a regular pace and with a normal rhythm.
Implantable atrial defibrillators are still considered experimental. They are devices that function like pacemakers, delivering electrical impulses to keep the heart's rhythm on course over the long term. Because the shock they deliver can be strong and somewhat painful, they are best sited to those with intermittent, rather than chronic, AF.
In the Maze procedure, a surgeon carefully makes a number of small cuts in the atrial wall, thus designing a maze of new pathways through which electrical signals can travel. As the signals travel through this newly created maze instead of randomly leaping from various parts of the heart, AF is reduced. This is currently an open-heart surgery that requires the use of a heart-lung machine, but researchers are working to achieve the same goal with a catheter or other minimally invasive techniques.

Research into potential new treatments is ongoing. Some of the more recent findings include:

A protein found in a certain type of tarantula venom was found to help open channels in the heart's conduction system, according to a study published in Nature (January 2001). When tested in rabbits, the protein GsMtx-4 successfully blocked atrial fibrillation. The protein is not toxic because the venom is from a type of tarantula whose bite is not harmful to humans. GsMtx-4 is promising as an antiarrhythmic medication because it treats the cause of the arrhythmia, rather than the symptoms.
A study published in Circulation (November 2000) found an investigational form of ablation to be an effective treatment for atrial fibrillation. In the study, 26 patients with resistant atrial fibrillation (12 permanent and 14 paroxysmal) were treated with the experimental form of ablation to isolate the pulmonary veins from the left atrium. After nine months, 85 percent of the patients remained free from atrial fibrillation, regardless of whether they were taking antiarrhythmic medications. However, this approach remains investigational.

Knowing the most common AF risk factors can help in preventing or recognizing symptoms. These risk factors include:

Age (about one percent of adults over 60 experience AF)
Coronary artery disease
Hypertension (high blood pressure)
Congenital heart disease
Thyroid disease
Inflammation of the heart lining (pericarditis)
Previous heart attack
Congestive heart failure
Chronic lung disease, such as asthma, or other pulmonary conditions that cause a shortage of oxygen in the blood such as chronic obstructive pulmonary disease (COPD)
Alcohol abuse
Illegal drug abuse (e.g., cocaine)
Excessive caffeine or decongestant use
Mitral valve dysfunction

In rare cases (estimated at one in 10,000) young adults can experience AF without any risk factors or underlying heart disease. This is referred to as lone atrial fibrillation and is often associated with stress and/or the use of drugs or alcohol.

People are encouraged to speak with their physician if they feel a flutter, skipped beat or any other unusual beat activity. Those who continue to experience symptoms of AF even after treatment are also urged to contact their physician immediately. Many AF patients are able to live normal, active lives.

Ventricular fibrillation and atrial flutter

A quite different (and life threatening) condition is ventricular fibrillation. Ventricular fibrillation involves a quivering of the ventricles instead of the atria. Unlike AF, it is life threatening because it results in 350 beats per minute or higher. The heart cannot keep that rate up for more than a few minutes without treatment (e.g., with a defibrillator).

A rhythm that is closely related to atrial fibrillation is atrial flutter, in which a very rapid but regular electrical signal in the atria causes a very rapid heartbeat. It is not unusual for patients to experience episodes of atrial fibrillation at some times and atrial flutter at others. As with atrial fibrillation, a normal rhythm can be restored by either cardioversion or medication. In contrast to atrial fibrillation, atrial flutter can generally be cured by catheter ablation.