Text Box: CATHETE ABLATION OF TACHYARRHYTHMIAS USING IMPROVED MAPPING METHOD AND NEW TECHNIQUE IN CHILDREN Zeng Shaoying, Wang Huishen, Yang Pinzhen, et al Department of Pediatrics, Guangdong Cardiovascular Disease Institute, Guangzhou, China Objective: Summing up the experience of Using improved mapping method and new technique to ablate tachyarrhythmias in children. Methods: 1) Swartz length sheath: They are used in 35 cases with right sided pathway and slow pathway and atrial tachycardia (AT) and atrial flutter(AF); 2) Reference electrodes: After two electrodes were replaced in right ventricular outflow and ventricular inflow,“encircling” mapping technique was used, Ablation catheter was positioned at the site where reference electrode recorded the earliest ventricular activation; 3) RF current was applied at the site where the high frequency potential preceded the local ventricular activation and was late than His bundle electrogram 20 msec during sinus rhythm in two cases with idiopathic left ventricular tachycardia (ILVT); 4) CARTO system: We used CARTO system to map and ablate three cases with AT(focal and reentrant)and one case with AF and one case with ILVT. Results: All forty cases were successfully ablated with 5.0±3.8RF pulses, The fluoroscopic time was 25±12.4 min. Conclusion: They could significantly reduced RF pulses and fluoroscopic time when we mapped and ablated tachyarrhythmia in children. to use improved mapping method and new technique; especially CARTO system can overcome difficult cases before. 1874