ABSTRACT
Para-Hisian accessory pathway (AP) means the AP locate about 0. 5cm above or under the His bundle. To identify the AP location,the big tip catheter mapping must be under sinus rhythm,ventricular pacing and inducing SVT in order to avoid injury of His bundle. During ablation process, the surface morphology and juctional escape rhythm must be observed. If RF must be done under ventricular pacing, once ablating effect is confirmed,the pacing would be stopped and escape rhythm can be observed. If ante-grade condution are always through AP in SVT and endocardial mapping are confirmed multipe APs and AVN are bystander in SVT, we do not exclude abmormal growth in AVN. It can be ablated retrograde AP to treat SVT and should be avoided to ablate antigrade AP.