Abstract
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.
Keywords: atrial fibrillation, catheter ablation, rotor, fibrosis, late-gadolinium enhancement magnetic resonance imaging
Introduction
Pulmonary vein isolation (PVI) is an established ablation strategy for patients with paroxysmal AF, but the impact is much less in patients with persistent AF.1 Late-gadolinium enhancement magnetic resonance imaging (LGE-MRI) has been reported to detect myocardial fibrosis. Furthermore, the progression of atrial fibrosis could be associated with AF recurrence after catheter ablation.2 A computer simulation could excellently demonstrate that AF drivers are observed in patchy fibrotic tissue, but not in dense tissue.3 This indicated the importance of a qualitative and quantitative analysis of fibrotic tissue. However, this has not been validated in humans. Recently, modulation of AF rotors has been proposed as one of the effective ablation strategies for persistent AF.4 A novel phase mapping system (ExTRa MappingTM; Nihon Kohden, Japan) has been developed and could provide us with a real-time and fully-automatic creation of each phase map movie, which could identify the location of AF rotors. Our aim of this study was to clarify the relationship between AF rotors detected by the ExTRa Mapping and the tissue properties assessed by LGE-MRI.
Methods