JAMA: Atrial Fibrillation Basics The heart has 4 chambers: the left and right atria (upper chambers) and the left and right ventricles (lower chambers). A normal heartbeat begins in the right atrium. The sinoatrial (SA) node is a cluster of cells that are responsible for initiating an electrical signal that is transmitted between the heart muscles. This signal causes the atria to contract, pumping blood from the atria into the ventricles, and the signal is then transmitted to the atrioventricular (AV) node and the ventricles. Atrial fibrillation (AF) is a common arrhythmia when the ventricles contract. The heart has four chambers: the left and right atria (upper chambers) and the left and right ventricles (lower chambers). A normal heartbeat begins in the right atrium. The sinoatrial (SA) node is a cluster of cells that are responsible for initiating an electrical signal that is transmitted between the heart muscles. This signal causes the atria to contract, pumping blood from the atria into the ventricles, and the signal is then transmitted to the atrioventricular (AV) node and the ventricles. When the ventricles contract, blood is pumped into the lungs and throughout the body. Heart rate is the number of times your heart beats per minute. The heart rhythm (heart beat), on the other hand, is the regularity of your heartbeat. With a normal heart rhythm, the heartbeats are equally spaced. In atrial fibrillation, the heart conducts an uncoordinated electrical signal. This disordered electrical signal starts in a part of the heart other than the SA section, resulting in one rapid and irregular heartbeat. During an episode of atrial fibrillation, the heart does not pop out blood efficiently. Atrial fibrillation episodes may be brief or may last for a long time. Causes of atrial fibrillation Diseases that affect the heart are common causes of atrial fibrillation. These diseases include heart failure, heart valve disease, high blood pressure, and heart attack. Other causes include obesity, chronic obstructive pulmonary disease, structural abnormalities of the heart, hyperthyroidism, and alcoholism. Symptoms Some patients experience symptoms of atrial fibrillation such as palpitations (a sensation in the chest like the beating of wings), shortness of breath, chest pain, dizziness and fatigue. Others have no symptoms and may not know they have atrial fibrillation. A doctor may find an abnormal heart rhythm once during a physical exam; or he or she may find atrial fibrillation during an electrocardiogram for another condition. Treatment The treatment of atrial fibrillation varies from person to person. Doctors will consider medical history and symptoms before recommending a treatment plan. Treatment goals include maintaining a normal heart rate and heart rhythm (cardiac rhythm) and preventing strokes. For many patients, controlling the heart rate with medication is done to help maintain a normal heart rate by slowing the conduction of electrical signals in the atrioventricular (AV) node. For some patients, the best option for rhythm control may be AV node ablation (destruction) and placement of a pacemaker. To help maintain the heart’s normal rhythm, doctors may prescribe anti-arrhythmic drugs. There is also a treatment known as electrical cardioversion, which uses electric shocks (or, rarely, drugs to produce an electric shock effect) to restore a normal rhythm. Catheter ablation uses small electrodes to destroy the heart muscle tissue that produces the abnormal electrical signal. Atrial fibrillation increases the risk of stroke. One rapid, irregular heartbeat can cause blood to concentrate in the atria and may produce blood clots. Many patients with atrial fibrillation are prescribed anticoagulants (prescription drugs that help prevent blood clots from forming). Anticoagulation is especially important for female patients with atrial fibrillation who are 65 years of age or older and have a history of congestive heart failure, hypertension, stroke, transient ischemic attack, vascular disease, or diabetes mellitus.