Atrial fibrillation

Atrial fibrillation (AF, AFib or A-fib) is an abnormal heart rhythm (arrhythmia) characterized by rapid and irregular beating of the atrial chambers of the heart. It often begins as short periods of abnormal beating, which become longer or continuous over time. It may also start as other forms of arrhythmia such as atrial flutter that then transform into AF.

Episodes can be asymptomatic. Symptomatic episodes may involve heart palpitations, fainting, lightheadedness, loss of consciousness, or shortness of breath. Atrial fibrillation is associated with an increased risk of heart failure, dementia, and stroke. It is a type of supraventricular tachycardia.

Atrial fibrillation frequently results from bursts of tachycardia that originate in muscle bundles extending from the atrium to the pulmonary veins. Pulmonary vein isolation by transcatheter ablation can restore sinus rhythm. The ganglionated plexi (autonomic ganglia of the heart atrium and ventricles) can also be a source of atrial fibrillation, and are sometimes also ablated for that reason. Not only the pulmonary vein, but the left atrial appendage and ligament of Marshall can be a source of atrial fibrillation and are also ablated for that reason. As atrial fibrillation becomes more persistent, the junction between the pulmonary veins and the left atrium becomes less of an initiator and the left atrium becomes an independent source of arrhythmias.

High blood pressure and valvular heart disease are the most common modifiable risk factors for AF. Other heart-related risk factors include heart failure, coronary artery disease, cardiomyopathy, and congenital heart disease. In low- and middle-income countries, valvular heart disease is often attributable to rheumatic fever. Lung-related risk factors include COPD, obesity, and sleep apnea. Cortisol and other stress biomarkers, as well as emotional stress, may play a role in the pathogenesis of atrial fibrillation.

Other risk factors include excess alcohol intake, tobacco smoking, diabetes mellitus, subclinical hypothyroidism, and thyrotoxicosis. However, about half of cases are not associated with any of these aforementioned risks. Healthcare professionals might suspect AF after feeling the pulse and confirm the diagnosis by interpreting an electrocardiogram (ECG). A typical ECG in AF shows irregularly spaced QRS complexes without P waves.

Healthy lifestyle changes, such as weight loss in people with obesity, increased physical activity, and drinking less alcohol, can lower the risk for AF and reduce its burden if it occurs. 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 convert AF to normal heart rhythm and is often necessary for emergency use if the person is unstable. Ablation may prevent recurrence in some people. For those at low risk of stroke, AF does not necessarily require blood-thinning though some healthcare providers may prescribe an anti-clotting medication. Most people with AF are at higher risk of stroke. For those at more than low risk, experts generally recommend an anti-clotting medication. Anti-clotting medications include warfarin and direct oral anticoagulants. While these medications reduce stroke risk, they increase rates of major bleeding.

Atrial fibrillation is the most common serious abnormal heart rhythm and, as of 2020, affects more than 33 million people worldwide. As of 2014, it affected about 2 to 3% of the population of Europe and North America. The incidence and prevalence of AF increases. In the developing world, about 0.6% of males and 0.4% of females are affected. The percentage of people with AF increases with age with 0.1% under 50 years old, 4% between 60 and 70 years old, and 14% over 80 years old being affected. The first known report of an irregular pulse was by Jean-Baptiste de Sénac in 1749. Thomas Lewis was the first doctor to document this by ECG in 1909.