Introduction | Objectives: Pulmonary vein isolation (PVI) with the Thomas ring (TR, single ring posterior wall isolation) has been shown to reduce recurrence of primarily paroxysmal atrial fibrillation (AF). Atrial fibrosis, as an important pathophysiological contributor, is directly linked to AF recurrence and resistance to therapy. The effect of TR ablation on outcomes of persistent AF (peAF) with advanced atrial fibrosis has not been adequately studied.

Methods: Observational series of three peAF patients (Tab.) who underwent TR. The degree of atrial fibrosis was determined by electroanatomic bipolar voltage mapping (CARTO, Diamond Bar, CA, USA). The reduced voltage areas (Fig.) reflected the degree and location of fibrotic substrate in the left atrium.

Results: Diffuse and very low voltage areas, indicating severe fibrotic atrial myopathy, were found in all three patients, with a preponderance for the posterior wall. After ablation, two of three patients remained in sinus rhythm (S), one case of AF recurrence was observed during short‐term follow‐up.

Conclusions: TR may be effective in preventing peAF recurrence with late stage atrial fibrosis. However, more data and longer follow‐up are needed.