Atrial fibrillation is an arrhythmia in the top chambers of the heart (atria) causing uncoordinated muscular contractions that weaken the heart’s ability to pump. It is characterized by rapid and irregular beating.

Often it starts as brief periods of abnormal beating which become longer and possibly constant over time. Most episodes have no symptoms. Occasionally there may be heart palpitations, fainting, shortness of breath, or chest pain. The disease increases the risk of heart failure, dementia, and stroke.

Although atrial fibrillation itself usually isn’t life-threatening, it is a serious medical condition that sometimes requires emergency treatment.

Hypertension and valvular heart disease are the most common alterable risk factors for AF. Other heart-related risk factors include heart failure, coronary artery disease, cardiomyopathy, and congenital heart disease. In the developing world, valvular heart disease often occurs as a result of rheumatic fever. Lung-related risk factors include COPD, obesity, and sleep apnea.

Other factors include excess alcohol intake, diabetes mellitus, and thyrotoxicosis. However, half of cases are not associated with one of these risks.

A diagnosis is made by feeling the pulse and may be confirmed using an electrocardiogram (ECG). The typical ECG shows no P waves and an irregular ventricular rate.

AF is often treated with medications to slow the heart rate to a near normal range (known as rate control) or to convert the rhythm to normal sinus rhythm (known as rhythm control). Electrical cardioversion can also be used to convert AF to a normal sinus rhythm and is often used emergently if the person is unstable. Ablation may prevent recurrence in some people. Depending on the risk of stroke, either aspirin or anti-clotting medications such as warfarin or a novel oral anticoagulant may be recommended. While these medications reduce this risk, they increase rates of major bleeding.