Arrhythmogenic foci and the mechanisms of atrial fibrillation.

In this issue of the Circulation: Arrhythmia and Electrophysiology, Kurotobi et al1 determined the number of arrhythmogenic foci in atria provocable with isoproterenol infusion in patients with paroxysmal, persistent, and permanent atrial fibrillation (AF). The results show that persistent AF has more foci than paroxysmal AF. However, when AF persists for 12 months, the number of foci were reduced. The authors suggest that the increased number of foci probably is involved in the development of persistent AF. However, because this association is not observed for AF that persists for 12 months, the importance of these foci in AF maintenance remains unclear.