Distribution of AF substrate
To date, atrial fibrosis, LVA, CFAE, AF rotor were considered as AF substrates.3,11-14The left atrial fibrosis was visualized by the LGE-MRI and the LGE site was heterogeneously distributed in AF patients. Higuchi et al. reported that the LGE site was highly distributed in the left PV antrum near the posterior wall side and spread on the posterior and anterior wall with AF progression.15 The LGE was more widely distributed in patients with persistent AF compared with patients with paroxysmal AF, especially on the posterior and anterior wall. Notably, the LGE site was likely distributed around LAA on the anterior wall in the progressed AF patients. Our study also demonstrated that the patchy LGE site was predominantly distributed at PV antrum and LAA base, which was completely consistent with their results.
The LVA was reported to be mainly found in LA septum, anterior LA and LA posterior.16 Of interest, Chen et al. reported that LGE sites were present at 61% of LVAs, whereas LVAs were present at 28% of LGE sites.17 Those findings indicated that the distribution of the LGE sites could not completely overlapped with that of the LVAs. The LVA distribution could depend on the mapping resolution, pacing site, cardiac rhythm or use of the cardioversion. Furthermore, the patchy LGE site was sometimes underestimated which depended on the visualization method. This might be the reason why the distribution of the LVA were not completely concordant with that of the LGE.
The distribution of CFAE were most commonly located in the LA posterior and PV antral region.18The distribution of spatiotemporal electrogram dispersion area were equally distributed at PV, LAA, LA posterior, LA anterior and LA roof. The distribution was unlikely similar to that of the patchy LGE site. The relationship between CFAE, spatiotemporal electrogram dispersion area, LVA and atrial fibrosis were complex and it was still in debate.
AF driver detected by a 252-electrode vest for body surface mapping were predominantly located in the PV antrum and LA bottom, subsequently around the LAA.19 Their results were likely consistent with our results. Cochet et al. concluded that the number of AF driver related to the extent of LGE, with the location of AF driver clustering to LGE sites.20 This strongly indicated that the LGE site could be one of the possible AF substrates and it was considered as an ablation target, which strongly supported our ablation strategy.