Atrial fibrillation (also known as A Fib or AF) is an example of a supraventricular tachycardia that is not considered to be "PSVT." It is a condition in which the electrical activity of the atrium becomes very rapid and disorganized. Instead of the sinus node providing the normal electrical signals to the atrium, rapid circulating waves of abnormal electrical signals continuously stimulate the atrium. The atrial rate can exceed 400 beats per minute! Atrial fibrillation can occur intermittently, which is known as Paroxysmal Atrial Fibrillation (a paroxysm is a self-terminating episode), or it can be Persistent (meaning it doesn't stop on its own). When atrial fibrillation has been present for more than 6 months and there's little hope of restoring a normal rhythm, it is known as Permanent AF (previously known as "Chronic AF"). During atrial fibrillation, electrical signals from the atrium constantly bombard the AV node. The AV node usually passes a large number of these rapid signals to the ventricles, which often beat rapidly and irregularly. In fact, the overall rate of the ventricles varies tremendously, depending on the age of the patient, the health of the AV node, and whether medications to slow AV conduction (such as calcium-channel blockers or beta blockers) are present. Sometimes atrial fibrillation is caused by other conditions such as an overactive thyroid or excessive alcohol use. Sometimes it is associated with cardiac conditions such as coronary artery disease, high blood pressure, congestive heart failure, or valvular heart disease. Occasionally, it occurs in the absence of other cardiac conditions and is then called "lone" atrial fibrillation. Usually medicines are required to control the heart rate, and eventually restore a normal heart rhythm. Sometimes, the only way to stop the disorganized activity of the atrium is to get a large portion of all the atrial tissue to fire at the same time. This is done by sending an electrical shock across the chest in a procedure known as "electrical cardioversion." The shock stops the rapid disorganized atrial activity and allows the normal sinus rhythm to resume. Electrical cardioversion is usually done with deep sedation so that the patient doesn't remember anything. It is generally a safe procedure and is usually effective unless the atrial fibrillation has been present for months or years or unless the underlying heart disease is very severe.
Patients who have atrial fibrillation may be at increased risk of developing a blood clot within the nooks and crannies found in the atrial chambers. If such a blood clot breaks off and travels in the circulatory system, it can lead to a stroke. Strokes due to atrial fibrillation are very serious, and make up about 15% of all strokes. Most people who have atrial fibrillation must take some kind of blood thinner to decrease the risk of clots formation within the atria.