Backgrounds This study was to report the initial experiences of the technique of fusion of either MSCT or magnetic resonance imaging (MRI) with three-dimensional (3-D) electroanatomic mapping (CartoMerge) to guide circumferential pulmonary vein ablation (CPVA) for the treatment of atrial fibrillation (AF). Methods Fifty-five patients [42 men, mean age (SS + 14) years] with symptomatic drug-refractory AF underwent MRI or 64-slice MSCT 1 to 3 days prior to the ablation procedure. Using the new CartoMerge?Image Integration Module, 3-D anatomic images of the left atrium (LA) and pulmonary veins (PVs) derived from MRI/MSCT were established and fused with the electroanatomic map. The end-point of CPVA was abolish or dissociation of pulmonary vein potentials (PVPs). Results MRI and 64-slice MSCT was performed in 30 and 25 patients, respectively. A mean of (49±13) mapping points was used to establish the electroanatomic model of the LA/PVs. In all patients, MRI/MSCT images could be fused with the 3-D electroanatomic map. Mean distance between the mapping points and the MRI/MSCT surfaces ranged from (1.16±0.89) mm to (2.20±1.76) mm.Conclusions Integration of MRI/MSCT image and the 3-D electroanatomic mapping is a useful tool to facilitate ablation procedure for AF. However, the accuracy of the fusion procedure is dependent on the precision of electroanatomic mapping. Backgrounds This study was to report the initial experiences of the technique of fusion of either MSCT or magnetic resonance imaging (MRI) with three-dimensional (3-D) electroanatomic mapping (CartoMerge) to guide circumferential pulmonary vein ablation (CPVA) for the treatment of Fifty-five patients [42 men, mean age (SS + 14) years] with symptomatic drug-refractory AF underwent MRI or 64-slice MSCT 1 to 3 days prior to the ablation procedure. Using the new CartoMerge ™ Image Integration Module, 3-D anatomic images of the left atrium (LA) and pulmonary veins (PVs) derived from MRI / MSCT were established and fused with the electroanatomic map. The end-point of CPVA was abolish or dissociation of A mean of (49 ± 13) mapping points was used to establish the electroanatomic model of the LA / PVs. In all patients (PVPs). Results MRI and 64-slice MSCT were performed in 30 and 25 patients, respectively. , MRI / MSCT images could be fused with the 3-D electroanatomic map. Mean distance between the mapping points and the MRI / MSCT surfaces ranged from (1.16 ± 0.89) mm to (2.20 ± 1.76) mm. Conclusions Integration of MRI / MSCT image and the 3-D electroanatomic mapping is a useful tool to facilitate ablation procedure for AF. However, the accuracy of the fusion procedure is dependent on the precision of electroanatomic mapping.