A specific type of cardiac arrhythmia (abnormal heartbeat) in which the upper chambers of the heart beat erratically. Atrial fibrillation, which affects more than 2 million Americans, is usually not life threatening, but it may increase the risk of stroke and congestive heart failure.
The heart has four chambers: two at the top called atria and two at the bottom called ventricles. During each heartbeat, the chambers contract in a synchronized fashion: First the atria contract to fill the ventricles with blood; then the ventricles contract, sending blood into the circulation as the atria relax to fill with blood again. Healthy circulation depends on the coordinated movement of all four chambers, which is regulated by a cluster of cells in the right atrium called the sinus node. When this coordinated movement gets disrupted, the result is cardiac arrhythmia. The heart may beat too slowly (called bradycardia) or too fast (called tachycardia). Atrial fibrillation is a type of tachycardia in which the atrial chambers beat fast — sometimes contracting as many as 300–400 times per minute — and chaotically.
People with heart disease, thyroid conditions, diabetes, or high blood pressure have a higher risk of developing atrial fibrillation. People with atrial fibrillation may experience such symptoms as heart palpitations (the sensation of pounding, irregular heartbeats), weakness, lightheadedness, shortness of breath, and chest pain.
Doctors use a number of different methods to diagnose atrial fibrillation, including the following:
- An electrocardiogram can be used to monitor the electrical activity of the heart.
- A Holter monitor is sometimes used to detect arrhythmia outside the doctor’s office since the arrhythmia may happen at unpredictable times. (A Holter monitor is a portable electrocardiographic device that monitors the heart’s electrical activity as a person carries out his usual daily activities.)
- An echocardiogram uses sound waves to generate a moving image of the heart.
- Blood tests are sometimes used to detect thyroid disease or other abnormalities that may cause atrial fibrillation.
Treatment for atrial fibrillation is designed to restore the heart’s normal rate and rhythm and to prevent blood clots. Drugs commonly used to restore normal heart rhythm include amiodarone (brand names Cordarone and Pacerone), propafenone (Rythmol), and sotalol (Betapace, Sorine). The normal rhythm may also be restored using electrical cardioversion, in which an electrical shock is delivered to the heart using paddles or patches placed against the chest. Digoxin (Lanoxin, Digitek) is sometimes used to slow the heart rate, sometimes in combination with other drugs called calcium channel blockers and beta-blockers, which are often used to treat high blood pressure. In people at high risk for stroke, doctors prescribe anticoagulants, or blood-thinning drugs, such as warfarin (Coumadin), which can prevent the formation of blood clots that might trigger a stroke.
In severe cases of atrial fibrillation that aren’t helped by drugs, more intensive treatments may be used. Sometimes a pacemaker, an electronic device that helps regulate the heartbeat, is surgically implanted. It may be needed if the drugs used to treat atrial fibrillation are causing the heart to beat too slowly. In some cases, the atrioventricular node, which ordinarily sends electrical signals from the atria to the ventricles, is ablated (destroyed) using radiofrequency energy delivered to the heart through a long, slender tube called a catheter. A pacemaker is then used to regulate the heartbeat.