Etiology and Pathogenesis of Atrial Fibrillation

Atrial fibrillation (AF) is a common arrhythmia whose causes and pathogenesis involve multiple aspects including cardiac structure, electrophysiology, and arrhythmogenic mechanisms.

1. AF typically is associated with atrial myocardial fibrosis, inflammation, oxidative stress, and abnormal regulation of the autonomic nervous system. Cardiac diseases such as coronary artery disease, hypertension, valvular heart disease, and cardiomyopathy can alter the structure and function of the atria, leading to abnormal electrophysiological activity that triggers AF.

2. It may occur secondarily to other arrhythmias, such as atrial tachycardia or atrial flutter.

3. Non-cardiac factors such as hyperthyroidism, pulmonary diseases, electrolyte disturbances, and alcohol consumption also can promote the occurrence of AF by affecting the cardiac electrophysiological properties.

The main mechanisms involved in the development of AF include the following:

1. Automatic focal mechanism: abnormal ectopic discharge foci appear within the atria, typically located in the pulmonary veins, superior vena cava, and posterior free wall of the left atrium, which can trigger AF.

2. Multiple wavelet reentry: reentrant circuits form within the atria, with generally 3–5 wavelets, which can occur in various regions of the atria.