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Mechanisms of atrial fibrillation

Brian Olshansky, MD
Rishi Arora, MD
Section Editors
Bradley P Knight, MD, FACC
Hugh Calkins, MD
Deputy Editor
Gordon M Saperia, MD, FACC


Atrial fibrillation (AF) is a most common cardiac arrhythmia. The chance of developing AF is tied closely to age, with AF rare before the age of 50 years. In addition to age, there are many types of cardiac and medical conditions that are also closely linked to AF. These include hypertension, coronary artery disease, heart failure, valvular heart disease, obesity, and sleep-apnea syndrome. It is well established that high levels of alcohol can increase the probability of developing AF, and that hyperthyroidism can cause AF. Evidence for caffeine and energy drinks, while suspected, is questionable [1]. It is also well established that AF is more common in individuals who have a first-degree relative who developed AF at a young age. (See "Epidemiology of and risk factors for atrial fibrillation".)

The precise mechanisms by which age and the other conditions listed above increase the propensity for development of AF are understood poorly (figure 1). However, these conditions may impact the triggers for AF, which commonly arise in the pulmonary veins or the substrate for maintenance of AF, which broadly relates to atrial size and the extent of fibrosis. Some of the factors that may play a role in the mechanisms of AF include autonomic tone, inflammation, atrial pressure and wall stress, and genetics. (See "Epidemiology of and risk factors for atrial fibrillation", section on 'Other factors'.)

This topic will provide a broad overview of the current understanding of the mechanisms of AF. This discussion will provide a relatively simplistic approach to a complex topic. The reader will be referred to a rapidly growing literature on this topic, including some comprehensive reviews [2].


The following terms are defined to help the reader’s understanding of the material below:

Trigger – a rapidly firing focus often arising in the pulmonary veins that can initiate atrial fibrillation (AF).

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Literature review current through: Nov 2017. | This topic last updated: Nov 25, 2015.
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