A typical pattern of activation in the right atrium during paroxysmal atrial fibrillation: the washing-machine phenomenon.

Atrial fibrillation affects a large population of patients. The electrophysiological mechanisms that initiate and maintain atrial fibrillation may be multiple. Even if some studies exploring right atrial activation have been recently published, data concerning atrial fibrillation activation patterns and its mechanisms are still scarce and controversial. This study supplies information on right atrial activation during atrial fibrillation. Twenty-four patients with recurrent, drug-refractory, lone paroxysmal atrial fibrillation underwent an extensive mapping of the right atrium. A pattern of organized atrial fibrillation (type 1) was noted in the trabeculated right atrium and atrial roof, characterized by discrete atrial electrograms, separated by an isoelectric baseline, with a continuous switching between clockwise and counterclockwise activation that we called washing-machine phenomenon. In the majority of patients, recordings from the anterior and medial areas of the atrial septum, showed fractionated electrograms consistent with a more disorganized activation pattern. Atrial activation in the inferior septum and coronary sinus was rather disorganized, neither synchronized with the activation sequence of the trabeculated right atrium nor with that of the anterior septum. Furthermore, the activation pattern showed fractionated electrograms and a variability of the isoelectric baseline similar to that recorded in the septum. No significant complications were reported during the procedure. In conclusion, mapping of the right atrium during induced atrial fibrillation shows a very typical pattern of activation in the trabeculated right atrium that we called the washing-machine phenomenon. Whether this sequence of activation represents a bystander situation or an active conditioning factor needs further investigations.