Atrial fibrillation may be triggered by focal initiators. Recent experimental work indicates that ectopic atrial activation may emerge from one more foci located in the muscular sleeves of the proximal pulmonary veins as single beats or repetitive bursts of activity. This focal-triggered atrial fibrillation is often paroxysmal in its early stages, and it may be observed in individuals with structurally normal hearts. The focal-triggered mechanism may also underlie some cases of persistent atrial fibrillation in the presence or absence of structural heart disease. It appears that the presence of atrial foci functioning as triggers localized in the pulmonary veins is a finding in many patients with lone or idiopathic and paroxysmal atrial fibrillation. In this group of patients, segmental or circumferential pulmonary vein ablation has an emerging role.

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