The Location of the Potential FCB Region
Critical areas of arrhythmogenesis often occur in diseased tissue with low-voltage areas that indicate the scarring zone. The potential in scar areas could be recorded as ESAs, LDPs or FPs, each of which acts instead of a different mechanism on arrhythmias.8-11 One AT that converted to another kind of AT during ablation could occur due to various causes (abnormal automaticity, triggered activity or reentry). The FCB region we described in this study was more common with scar-related reentry and often could be found near the scarring zone. While the potential of these regions could convert between DPs, FPs and normal potential formation in the different ATs, it was still low voltage compared with that of normal tissue in some ATs or sinus rhythms. This electrophysiological feature in large part may be due to scarring of the atrium due to various heart diseases, while normal tissue could not be seen. Second, except for the effect of the scarring, the regions where FCBs occurred were observed more commonly in the junction between the left atrial appendage and anterior wall of the left atrium (in 3) and the junction between the roof and atrium of the left superior PV (in 2), where Bachmann’s bundle is located.12 These positions are associated with fiber crisscrosses that may exhibit more electric anisotropy. The scarring may affect the homogeneity of conduction in one orientation during ATs. In patients with previous AF ablation, the first MAT may be due to the circumferential pulmonary vein isolation (CPVI), and the FCB would be related to damage to the previous ablation line.