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
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.