Objective      To explore the clinical value of the electroanatomical CARTO three-dimensional mapping system guiding in assessment of electrophysiological features of macroreentry atrial tachycardia (MAT) and in the efficiency of radiofrequency ablation.       Methods      Clinical data of 38 MAT patients who received the above therapy in our hospital from August 2009 to September 2011 were collected. There were 17 males and 21 females at the age of (48. 4±10. 8)

15 patients has persistent/or permanent tachycardia

and 12 patients had right atrial enlargement among the 31 patients with MAT from right atrium. No surgery or catheter ablation was present in 27 patients. In the 31 patients

54.8％（17of 31）had single reentrant cycle and 45.2％（14 of 31）were complicated by other tachycardia in those cases. Conventional electrophysiological study was performed to determine the location of MAT before the three-dimensional electroanatomic mapping. Using voltage and activation maps guided by CARTO mapping system

the mechanism of tachycardia was analyzed and the slow conduction areas (critical isthmus) were verified. Radiofrequency energy was delivered using irrigated-tip catheter.       Results      The cavotricuspid isthmus was ablated in all those 31 patients with MAT from right atrium

and the termination of atrial flutter was obtained in 30 cases. The successful ablation termination point was obtained in 16 patients with single reentrant cycle after only isthmus ablation

but ablation of other sites was simultaneously performed in other 14 cases. All of 7 patients with MAT from left atrium were post-ablation

the central conduction obstacle (GAP) was existed at the previous ablation line in 4 cases and at the mitral isthmus in 3 cases

and the successful ablation was obtained in 6 patients. The successfully-ablated rate was 94.7% in this study (36/38) at discharge. During the follow-up of (18.6±4.5) months

7 patients were recurred

in which 5 patients were successfully re-ablated. Therefore

tachy-arrhythmia free rate was 89.5 % (34/38) during the follow-up．       Conclusion      MAT form right atrium is often related to cavotricuspid isthmus and sponaneous scarring

but MAT from left atrium is usually related to surgery or ablation. CARTO three-dimensional electroanatomic mapping system is helpful for an effective ablation in complicated tachycardia.