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.[11][12] It often begins as short periods of abnormal beating, which become longer or continuous over time.[4] It may also start as other forms of arrhythmia such as atrial flutter that then transform into AF.[13]
Atrial fibrillation
Auricular fibrillation[1]
> age 50[4]
Feeling the pulse, electrocardiogram[8]
Lifestyle modifications, rate control, rhythm control, anticoagulation[5]
2.5% (developed world), 0.5% (developing world)[4]
315,000 with atrial flutter (2019)[10]
Episodes can be asymptomatic.[3] Symptomatic episodes may involve heart palpitations, fainting, lightheadedness, loss of consciousness, shortness of breath, or chest pain.[2] Atrial fibrillation is associated with an increased risk of heart failure, dementia, and stroke.[3][12] It is a type of supraventricular tachycardia.[14]
High blood pressure and valvular heart disease are the most common modifiable risk factors for AF.[5][6] Other heart-related risk factors include heart failure, coronary artery disease, cardiomyopathy, and congenital heart disease.[5] In low- and middle-income countries, valvular heart disease is often attributable to rheumatic fever.[15] Lung-related risk factors include COPD, obesity, and sleep apnea.[3] Cortisol and other stress biomarkers (including vasopressin, chromogranin A, and heat shock proteins), as well as emotional stress, may play a role in the pathogenesis of atrial fibrillation.[16]
Other risk factors include excess alcohol intake, tobacco smoking, diabetes mellitus, and thyrotoxicosis.[3][7][15] However, about half of cases are not associated with any of these aforementioned risks.[3] Healthcare professionals might suspect AF after feeling the pulse and confirm the diagnosis by interpreting an electrocardiogram (ECG).[8] A typical ECG in AF shows irregularly spaced QRS complexes without P waves.[8]
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.[17] 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).[5] Electrical cardioversion can convert AF to normal heart rhythm and is often necessary for emergency use if the person is unstable.[18] Ablation may prevent recurrence in some people.[19] For those at low risk of stroke, AF does not necessarily require blood-thinning though some healthcare providers may prescribe aspirin or an anti-clotting medication.[20] For those at more than low risk, experts generally recommend an anti-clotting medication.[20] Anti-clotting medications include warfarin and direct oral anticoagulants.[20] Most people with AF are at higher risk of stroke.[21] While these medications reduce stroke risk, they increase rates of major bleeding.[22]
Atrial fibrillation is the most common serious abnormal heart rhythm and, as of 2020, affects more than 33 million people worldwide.[3][17] As of 2014, it affected about 2 to 3% of the population of Europe and North America.[4] This was an increase from 0.4 to 1% of the population around 2005.[23] In the developing world, about 0.6% of males and 0.4% of females are affected.[4] 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.[4] A-fib and atrial flutter resulted in 193,300 deaths in 2015, up from 29,000 in 1990.[24][25] The first known report of an irregular pulse was by Jean-Baptiste de Sénac in 1749.[3] Thomas Lewis was the first doctor to document this by ECG in 1909.[3]
History[edit]
Because the diagnosis of atrial fibrillation requires measurement of the electrical activity of the heart, atrial fibrillation was not truly described until 1874, when Edmé Félix Alfred Vulpian observed the irregular atrial electrical behavior that he termed "fremissement fibrillaire" in dog hearts.[174] In the mid-18th century, Jean-Baptiste de Sénac made note of dilated, irritated atria in people with mitral stenosis.[175] The irregular pulse associated with AF was first recorded in 1876 by Carl Wilhelm Hermann Nothnagel and termed "delirium cordis", stating that "[I]n this form of arrhythmia the heartbeats follow each other in complete irregularity. At the same time, the height and tension of the individual pulse waves are continuously changing".[176] Correlation of delirium cordis with the loss of atrial contraction, as reflected in the loss of a waves in the jugular venous pulse, was made by Sir James MacKenzie in 1904.[177] Willem Einthoven published the first ECG showing AF in 1906.[178] The connection between the anatomic and electrical manifestations of AF and the irregular pulse of delirium cordis was made in 1909 by Carl Julius Rothberger, Heinrich Winterberg, and Sir Thomas Lewis.[179][180][181]
Other animals[edit]
Atrial fibrillation occurs in other animals, including cats, dogs, and horses.[182][183] Unlike humans, dogs rarely develop the complications that stem from blood clots breaking off from inside the heart and traveling through the arteries to distant sites (thromboembolic complications).[182] Cats rarely develop atrial fibrillation but appear to have a higher risk of thromboembolic complications than dogs.[182]
Cats and dogs with atrial fibrillation often have underlying structural heart disease that predisposes them to the condition.[182] The medications used in animals for atrial fibrillation are largely similar to those used in humans.[182] Electrical cardioversion is occasionally performed in these animals, but the need for general anesthesia limits its use.[182] Standardbred horses appear to be genetically susceptible to developing atrial fibrillation.[183] Horses that develop atrial fibrillation often have minimal or no underlying heart disease, and the presence of atrial fibrillation in horses can adversely affect physical performance.[183]