Objective   To evaluate the clinical value of the electroanatomical mapping Carto system in the guiding of radiofrequency ablation of atrial tachycardia (AT).    Methods   Totally 13 AT patients

7 males and 6 females at the age of （42.2±10.2）

including 3 patients failed in conventional radiofrequency ablation

who received the therapy from April 2007 to April 2009 in our hospital were studied. Three dimensional electroanatomical maps were constructed in the left or right atrium using electroanatomical mapping system (Carto). The type of AT (focal or macro reentrant) was identified by the electroanatomical maps

and the ablation targets were at the earliest activation sites or the isthmus of circuit.    Results   ① All 13 patients were confirmed as focal ATs

and 12 focal ATs were ablated successfully at the earliest activation sites

and one AT of right atria appendage was failed in ablation. The significant early A waves in 7 cases were recorded in His bundle or proximal part of coronary sinus catheter

and the activation maps demonstrated that the earliest activation sites were at the ostium of superior vena cava (n=3)

the ostium and the vicinity of coronary sinus (n=3) and ostia of right atria appendage (n=1) respectively. ②The significant early A waves in 3 cases were recorded in the distal part of coronary sinus catheter

and the activation maps demonstrated that the earliest activation sites were at the ostium of left superior pulmonary vein (n=2)

and the posterior wall of left atria appendage (n=1). ③ The relatively early A waves in 3 cases were recorded in the distal part of coronary sinus

and the activation maps demonstrated that the earliest activation sites were at the ostium of right inferior pulmonary vein (n=2)

and the noncoronary sinus of aorta (n=1). One complication of pericardial fluid occurred. During a follow-up period of 2 to 24 months

1 patient with focal AT recurred and underwent another ablation with  successful result.    Conclusion   These results suggest that electroanatomical mapping of AT may facilitate rapid and accurate identification of the type of AT

and guide ablation safely and effectively

especially in unsuccessful cases with conventional technique.