Abbreviations:
AF = atrial fibrillation
AWT = atrial wall thickness
CE-MRA = contrast-enhancement magnetic resonance angiography
CT = computed tomography
LA = left atrium
LAA = left atrial appendage
LGE-MRI = late-gadolinium enhanced magnetic resonance imaging
MRs = meandering rotors
MWs = multiple wavelets
NPAs = non-passively activated areas
PAs = passively activated areas
PV = pulmonary vein
PVI = pulmonary vein isolation
RA = right atrium
ROC = receiver operating characteristic
SD = standard deviation
3D = three-dimensional
%NP = non-passively activated ratio
Pulmonary vein isolation (PVI) is a well-established ablation strategy
for paroxysmal atrial fibrillation (AF), but it is much less effective
in persistent AF patients.1 Late-gadolinium enhanced
magnetic resonance imaging (LGE-MRI) has been reported to detect
myocardial fibrosis. Furthermore, the progression of atrial fibrosis
after catheter ablation may be associated with AF
recurrence.2 It has been previously reported that AF
drivers are observed in patchy LGE areas but not in dense LGE areas, in
computer simulation models.3 That shows the importance
of a qualitative and quantitative analysis of the LGE areas. Recently,
the modulation of the AF drivers has been proposed as one of the
effective ablation strategies for persistent AF.4 To
evaluate the location of AF drivers precisely, a novel phase mapping
system (ExTRa MappingTM; Nihon Kohden, Japan) has been
developed.5 ExTRa Mapping is a phase map based on
myocardial action potentials, which has been validated by
high-resolution optical membrane potential mapping in an animal
study.6 We previously reported that AF drivers
detected by the ExTRa Mapping were frequently found in heterogenous LGE
areas assessed by LGE-MRI in persistent AF patients. However, some of
them were also found in lesser LGE areas.7 This has
implied that there are other possible structural factors associated with
AF drivers. A previous computer simulation study demonstrated the role
of the atrial wall thickness (AWT) as a substrate for AF drivers and
marker for the identification of AF driver locations in patient-specific
atria, and the AWT gradients acted as anchoring points for AF drivers in
the absence of fibrosis.8 However, such an effect of
the AWT on AF drivers has not been fully verified in humans. The aim of
this study was to evaluate the impact of the AWT in lesser LGE areas on
AF drivers in persistent AF patients.