Differences in local directional heterogeneities. The degree of local directional heterogeneities of CV vectors during SR (turquoise/left) and PAC (red/right). The difference [Δ (PAC-SR)] between SR and PAC is visualized as median with interquartile range. *P < 0.05. BB, Bachmann’s bundle; CV, conduction velocity; LA, left atrium; LDH, local directional heterogeneities; PAC, premature atrial contraction; PVA, pulmonary vein area; RA, right atrium; SR, sinus rhythm.