ObjectiveAnalyzing the left atrium and pulmonary vein morphologicallv by 64 multislice spiral CT(MSCT)scan to guide the catheter ablation of Atrial fibrillation.MethodsTwo hundred and thirty-two patients(146 cases in atrial fibrillation group and 86 cases in control group)received 64 MSCT examination of the left atrium and pulmonary vein.The incidence of anatomical variation of pulmonary vein was compared between atrial fibrillation group and control group. For each group,the anatomical morphology ot every pulmonary vein and the auricle of left atrium was analyzed, the diameter of the orifice of each pulmonary vein and the size of left atrium were measured.ResultsSixty-four MSCT of left atrium and pulmonary vein could demonstrate detailed connecting type between left atrium and pulmonary Veins and the possible anatomieal variation. Anatomical variation of pulmonary vein in this study accounted for 16.8% (39/232)of total sample. For both groups,orifices of pulmonary veins appeared oval and their superoinferior diameters were larger than their anteroposterior diameters. There was significant difference in the inner diameter of left atrium between atrial fibrillation group and control group[atrial fibrillation group:(39.47±8.98)mm,control group:(36.94 ±5.49)mm,P=0.02],while there was no difference in the diameters of orifices ot puhnonary veins between two groups [ superoinferior diameters of pulmonary veins in atrial fibrillation group:left-up(18.15±1.35)mm,left-down(16.96 ±1.18)mm,right-up(17.50±