4.2 AF rotors and the PV antrum
Guillem et al. reported that rotors could be initiated by a focal ectopic discharge and wavefront break.11 The other previous studies demonstrated that the sleeve of the PV was thickest at the venoatrial junction and often consisted of 2 or more layers.12,13 Those anatomical findings indicated the presence of thick and anisotropic myocardial structures in the PV antrum. Thicker parts of the PVs with anisotropic properties may provide the substrate for a functional line of block during rotor activation. In this study, the NPAs were mostly found around the PV antrum, which was completely consistent with the previous study.10Furthermore, the tissue properties of the NPAs around the PV antrum also predominantly consisted of G2 and subsequently G1. The tissue properties of G1 indicated heterogenous and healthy tissue and this heterogeneity might have been caused by the wall thickness and anisotropic myocardial structures but not myocardial fibrosis.