Recurrent Post-Ablation Paroxysmal Atrial Fibrillation Shares Substrates With Persistent Atrial Fibrillation

![Figure][1] Objectives The purpose of this study was to determine the mechanistic overlap between paroxysmal and persistent forms of atrial fibrillation (AF), focusing on AF sources as a classification approach. Background The role of AF substrates is unclear in patients with paroxysmal AF (PAF) that recurs after pulmonary vein isolation (PVI). We hypothesized that patients with recurrent post-ablation (redo) PAF despite PVI have electrical substrates marked by rotors and focal sources and structural substrates that resemble persistent AF more than patients with (de novo) PAF at first ablation. Methods In 175 patients at 11 centers, we compared AF substrates in both atria using 64-pole basket catheters and phase mapping, and indices of anatomical remodeling between patients with de novo or redo PAF and first ablation for persistent AF. Results Sources were seen in all patients. More patients with de novo PAF (78.0%) had sources near pulmonary veins (PVs) than patients with redo PAF (47.4%; p = 0.005) or persistent AF (46.9%; p = 0.001). The total number of sources per patient (p = 0.444), and number of non-PV sources (p = 0.701) were similar between groups, indicating that redo PAF patients had residual non-PV sources after elimination of PV sources by prior PVI. Structurally, left atrial size did not separate de novo from redo PAF (49.5 ± 9.5 mm vs. 49.0 ± 7.1 mm; p = 0.956) but was larger in patients with persistent AF (55.2 ± 8.4 mm; p = 0.001). Conclusions Patients with PAF despite prior PVI show electrical substrates that resemble persistent AF more closely than patients with PAF at first ablation. Notably, these subgroups of PAF are indistinguishable by structural indices. These data motivate studies of trigger versus substrate mechanisms for patients with recurrent PAF after PVI. [1]: pending:yes