Anatomical relationship between abnormal conduction zone and contact area/low voltage area
All patients underwent ECG-gated 64-slice multidetector CT (SOMATOM Definition Edge; Siemens) with slice acquisition thickness set at 0.5 mm. The CoAs (ascending aorta-anterior LA, descending aorta-posterior LA, and vertebrae-posterior LA) were assessed using CT. The anatomical distance between those structures and the LA was calculated. CoA was defined as the distance between any external structures and LA was within 3 mm.13 Subsequently, we traced the CoAs inside the LA on each 2-mm CT slice, and three particular areas were created on the 3-D mapping system (Figure 2 ). The CoA size was manually measured on each segment. The anatomical relationship between the ACZ and CoAs/LVA at each cut-off value was analyzed (Figure 2 ). The overlapping rate of the ACZ and CoAs/LVA was assessed for each patient (Figure 1, 2 ).