Atrial fibrillation/flutter is a heart rhythm disorder (arrhythmia). It usually involves a rapid heart rate, in which the upper heart chambers (atria) are stimulated to contract in a very disorganized and abnormal manner.

Arrhythmias are caused by a disruption of the normal electrical conduction system of the heart.

Normally, the four chambers of the heart (two atria and two ventricles) contract in a very specific, coordinated way. The electrial impulse that signals your heart to contract in a synchronized way begins in the sinoatrial node (SA node). This node is your heart's natural pacemaker.

The signal leaves the SA node and travels through the two upper chambers (atria). Then the signal passes through another node (the AV node), and finally, through the lower chambers (ventricles). This path enables the chambers to contract in a coordinated fashion.

In atrial fibrillation, the atria are stimulated to contract very quickly and differently from the normal pattern. The impulses are sent to the ventricles in an irregular pattern. This makes the ventricles beat abnormally, leading to an irregular (and usually fast) pulse.

In atrial flutter, the ventricles may beat very fast, but in a regular pattern.

If the atrial fibrillation/flutter is part of a condition called sick sinus syndrome, the sinus node may not work properly. The heart rate may alternate between slow and fast. As a result, there may not be enough blood to meet the needs of the body.

Atrial fibrillation can affect both men and women. It becomes more common with increasing age.

Causes of atrial fibrillation include:

• Alcohol use (especially binge drinking)
• Congestive heart failure
• Coronary artery disease (especially after a heart attack or coronary artery bypass surgery)
• Heart surgery
• High blood pressure (hypertension)
• Hypertrophic cardiomyopathy
• Medications
• Overactive thyroid gland (hyperthyroidism)
• Pericarditis
• Valvular heart disease (especially mitral stenosis and mitral regurgitation)

You may not be aware that your heart is not beating in a normal pattern, especially if it has been occurring for some time.

Symptoms may include:

• Pulse that feels rapid, racing, pounding, fluttering, or too slow
• Pulse that feels regular or irregular
• Sensation of feeling the heart beat (palpitations)
• Shortness of breath while lying down
• Confusion
• Dizziness, light-headedness
• Fainting
• Fatigue

Note: Symptoms may begin or stop suddenly.

The health care provider may hear a fast heartbeat while listening to the heart with a stethoscope. The pulse may feel rapid, irregular, or both. The normal heart rate is 60 - 100, but in atrial fibrillation/flutter the heart rate may be 100 - 175. Blood pressure may be normal or low.

An ECG shows atrial fibrillation or atrial flutter. Continuous ambulatory cardiac monitoring -- Holter monitor (24 hour test) -- may be necessary because the condition often occurs at some times but not others (sporadic).

Tests to find underlying heart diseases may include:

• Coronary angiography
• Echocardiogram
• Electrophysiologic study (EPS)
• Exercise treadmill ECG
• Nuclear imaging tests

In certain cases, atrial fibrillation may need emergency treatment to to get the heart back into normal rhythm. This treatment may involve electrical cardioversion or intravenous (IV) drugs such as dofetilide, amiodarone, or ibutilide. Drugs are typically needed to keep the pulse from being too fast.

Long-term treatment varies depending on the cause of the atrial fibrillation or flutter. Medications to slow the heartbeat may include:

• Beta-blockers
• Calcium channel blockers
• Digitalis

Anti-arrhythmic medications may be used to get the heart back into a normal rhythm. These medications may work well in many people, but they can have serious side effects. Many patients may go back to atrial fibrillation even while taking these medications.

Blood thinners, such as heparin and warfarin (Coumadin) reduce the risk of a blood clot traveling in the body (such as a stroke). Because these drugs increase the chance of bleeding, not everyone will use them. Antiplatelet drugs such as aspirin or clopidogrel may also be prescribed. Your doctor will consider your age and other medical problems to decide which drug is best.

Some patients with atrial fibrillation, rapid heart rates, and intolerance to medication may need a catheter procedure on the atria called radiofrequency ablation.

For some patients with atrial flutter, radiofrequency ablation can cure the arrhythmia and is the treatment of choice. Some patients with atrial fibrillation and a rapid heart rate may need the radiofrequency ablation done directly on the AV junction (the area that normally filters the impulses coming from the atria before they move on to the ventricles).

Ablation of the AV junction leads to complete heart block. This condition needs to be treated with a permanent pacemaker.

The disorder is usually controllable with treatment. Many people with atrial fibrillation do very well.

Atrial fibrillation tends to become a chronic condition, however. It may come back even wtih treatment.

• Fainting (syncope), if atrial fibrillation and atrial flutter cause the pulse to be too quick or slow
• Heart failure
• Stroke, if clots break off and travel to the brain (drugs that thin the blood such as heparin and warfarin can reduce the risk)

Call your health care provider if you have symptoms of atrial fibrillation or flutter.

Follow the health care provider's recommendations for treating underlying disorders. Avoid binge drinking.

Fuster V, Rydén LE, Cannom DS, Crijns HJ, Curtis AB, Ellenbogen KA, et al. American College of Cardiology/American Heart Association Task Force on Practice Guidelines; European Society of Cardiology Committee for Practice Guidelines; European Heart Rhythm Association; Heart Rhythm Society. ACC/AHA/ESC 2006 Guidelines for the Management of Patients with Atrial Fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines. Circulation. 2006;114:e257-e354.

Noheria A, Kumar A, Wylie JV Jr., Josephson ME. Catheter ablation vs. antiarrhythmic drug therapy for atrial fibrillation: a systematic review. Arch Intern Med. 2008;168:581-586.

Doyle JF, Ho KM. Benefits and risks of long-term amiodarone therapy for persistent atrial fibrillation: a meta-analysis. Mayo Clin Proc. 2009;84:234-242.