Atrial fibrillation

A type of abnormality of the heartbeat (see arrhythmia, cardiac) in which the atria (see atrium) of the heart beat irregularly and rapidly. The ventricles (lower chambers) also beat irregularly. The heart’s pumping ability is reduced as a result. Atrial fibrillation can occur in almost any longstanding heart disease but is most often associated with heart-valve disorders or coronary artery disease. Sudden onset of atrial fibrillation can cause palpitations, angina, or breathlessness. The heart’s inefficient pumping action reduces the output of blood into the circulation. Blood clots may form in the atria and may enter the bloodstream and lodge in an artery (see embolism). Diagnosis of atrial fibrillation is confirmed by ECG. Digoxin or beta-blocker drugs may be given to control the heartrate. Atrial fibrillation of recent onset may be reversed by defibrillation. In most cases, anticoagulant drugs are given to reduce the risk of embolism.