(A) Two views showing the eight left atrial segments used for regional analysis. 1, anterior; 2, lateral; 3, left atrial appendage; 4, roof; 5, posterior; 6, mitral isthmus; 7, floor; 8, septum; MA, mitral annulus; LSPV, left superior pulmonary vein; LIPV, left interior pulmonary vein; RSPV, right superior pulmonary vein; RIPV, right inferior pulmonary vein. (B and C) Colour-coded voltage map in the posterior–anterior view from the NavX 3D electroanatomic mapping system with areas of low voltage (<0.5 mV) in grey and normal voltage in remaining colour scale. Note increased areas of low voltage in AF (B) compared with normal voltages in paced rhythm (C). Note the regions of highly fractionated and low-voltage (<0.5 mV) signals during AF in (B) do not display fractionation and have a normal voltage in paced rhythm (C).