Abstract: AIM:To investigate the results of radiofrequency catheter ablation of ventricular tachycardia (VT) guided by right ventriculography and CARTO electroanatomic mapping in patients after cardiac surgery for tetralogy of Fallot (TOF). METHODS: Included in the study were five patients (four males and one female, aged 6-38 years) who had palpitations and sustained VT for 2-16 years after cardiac surgery for TOF. Two patients had a history of syncope. All patients had been ineffectively treated with antiarrhythmic drugs. No ICD was implanted. Right ventricular angiography and CARTO electroanatomic mapping system were used for directing mapping and ablating VT. First, right ventriculography was conducted to show right ventricle anatomy and to locate the pulmonary valve. For mappable VT, the VT mapping techniques included activation, entrainment and voltage mapping using standard criteria, and radiofrequency energy was delivered to the sites. For unmappable VT, the site of origin was approximated by the site of pace mapping that generated QRS complexes similar to those of VT. Radiofrequency ablation was performed as linear lesions based on the location of the best pace map, the location of valvular anatomic boundaries and the substrate defined by the voltage mapping. The sites with late potential or fragmented potential were also ablated. Irrigated RF energy was delivered to all patients. RESULTS: Six morphologies of VT (five sustained and one nonsustained VT) were induced in five patients, including two morphologies of VT induced in one patient. Only one with nonsustained VT could be induced in one patient. The cycle lengths of VT were 230-310 msec. In three patients, mapping and ablation were performed during VT. In another two patients, mapping was performed during sinus rhythm because of unmappable VT. All 6 VT were caused by scar-related reentry and were eliminated successfully in five patients. During 12-30 months of follow-up, no VT recurred in the patients. CONCLUSION: Right ventricle and pulmonary artery valvular anatomy could well be demonstrated by right ventriculography. Surgical patch and scars could be located by CARTO system. Based on the matrix of arrhythmia, RF catheter ablation of VT in patients after cardiac surgery for TOF may have a high success rate and a low recurrence, especially of unmappable VT.