[Mechanisms of atrial fibrillation. Recent progress and therapeutic implications]

Atrial fibrillation is usually due to multiple microreentry circuits. However, in some cases, the initial arrhythmia inducing the atrial fibrillation may be an abnormal automatism, or a macroreentry. The initial abnormalities may induce a desynchronization due to multiple macroreentry circuits. The main factors of atrial vulnerability are intraatrial conduction disturbances and changes in refractory periods. Critical mass and effects of autonomic nervous system may also play a role. Shortened refractory periods and decreased conduction velocity imply a short wavelength and an important arrhythmogenic risk. On the other hand, the longer the duration of atrial fibrillation, the more refractory periods will shorten and the more atrium will become vulnerable: atrial fibrillation tends to beget atrial fibrillation because of an electrophysiologic remodelage. In some cases atrial fibrillation, if its duration is long and if its rate is high, may be responsible for the development of a tachycardiomyopathy. The knowledge of atrial fibrillation mechanism may have interesting therapeutic implications such as resynchronization of the atria by stimulation or ablation, for example in the approaches comparable to the maze operation.