Background: A computational model demonstrated that atrial fibrillation (AF) rotors could be distributed in patchy fibrotic tissue and play an important role in AF drivers. However, this was not validated in humans. Objective: The purpose of this study was to evaluate the fibrotic tissue properties of AF rotors in patients with persistent AF. Methods: A total of 287 segments in 15 patients with persistent AF (longstanding persistent AF in 9 patients) that underwent AF ablation were assessed. Non-passively activated areas (NPAs), where rotational activation (AF rotor) was frequently observed, were detected by the novel real-time phase mapping (ExTRa Mapping). Atrial fibrosis was detected by late-gadolinium enhancement magnetic resonance imaging (LGE-MRI), and the fibrotic heterogeneity and density were assessed by the entropy (LGE-entropy) and volume ratio of the enhancement voxel (LGE-volume ratio), respectively. Results: NPAs were found in 61 (21%) of 287 segments and were mostly found around the pulmonary vein antrum. A receiver operating characteristic curve analysis yielded an optimal cutoff value of 5.7 and 10% for the LGE-entropy and LGE-volume ratio, respectively. The incidence of NPAs was significantly higher at segments with an LGE-entropy of >5.7 and LGE-volume ratio of >10% than at the other segments (38 [30%] of 126 vs. 23 [14%] of 161 segments, p = 0.001). No NPAs were found at segments with an LGE-volume ratio of >50% regardless of the LGE-entropy. Conclusion: AF rotors are mostly distributed in relatively weak and much more heterogenous fibrotic tissue.

Background: Computer simulation model demonstrated that atrial fibrillation (AF) driver attached to the patchy fibrosis assessed by late gadolinium enhancement magnetic resonance imaging (LGE-MRI). However, it has not been well elucidated in patients with persistent AF. The aim of this study is to investigate whether radiofrequency (RF) application on the patchy LGE site (PLS) could terminate AF or convert to atrial tachycardia (AT) and improve the rhythm outcome. Methods: A total of 31consecutive persistent AF patients with PLS were enrolled (PLS ablation group, mean age: 69 ± 8 years, mean left atrial diameter: 42 ± 6 mm). AF direct termination or AT conversion during RF application on the PLS were defined as favorable response. The rhythm outcome was compared between the PLS ablation group and the propensity matched conventional ablation group. Results: Favorable response was found in 15 (48%) of 31 patients (AF termination in 7, AT conversion in 8 patients). AF recurrence at 12 months follow-up was significantly less in the PLS group as compared to the control group (4 (13%) of 31 patients vs. 11 (35%) of 31 patients, log-rank p = 0.019). In patients with favorable response, AT recurred in 1 (7%) of 15 patients but AF. Conclusions: The PLS ablation could terminate AF or convert to AT in half of the patients and improve the rhythm outcome as compared to the conventional ablation. No AF recurrence was documented in patients with a favorable response.