Thirty six g.o. men suffered AVRT with concealed left-lateral AP, 3-5 episodes per year, 20-30 minutes duration without hemodynamic compromise. Six month ago patient underwent unsuccessful ablation of concealed left lateral AP. Moreover, tachycardia became malignant (high-frequent 150 beats-min, incessant (lasting up to 18 h/day), resistant to AAD (Amiodarone, Verapamil), and led to development of tachycardia-induced cardiomyopathy (EF was 16%, and 2 episodes of pulmonary oedema). We performed redo EPS which verified AVRT with left-lateral AP conduction and it corresponded to criteria of PJRT with left-AP localization (lasting up to 12 h., retrograde decremental conduction only, incessant arrhythmia time course). We used transseptal approach and 3D-electroanatomic mapping systems for AP ablation. Mapping verified separated spike of AP potential at the left-lateral area during AVRT. Following ablation at this site abolished arrhythmia. There was no recurrence of arrhythmia 3 months after procedure. TTE showed increasing of EF from 16 to 39%. We can assume that the first RFA might led to the elimination of concealed antegrade conduction via AP which was a protective mechanism that prevented incessant time course of AVRT.