Abstract A 76 y.o. patient referred to our attention for syncopal and presyncopal episodes. His ECG showed several premature ventricular contractions (PVC) with the morphology of a right bundle branch block (RBBB)– positive concordance in precordial leads and transtion in V3 lead– and an inferior axis. Echocardiographic finding was a moderate reduced ejection fraction. Furthermore coronarography did not identify critical stenosis, excluding an ischemic etiology. Cardiac MRI was performed, confirming the reduce ejection fraction and excluding LGE. Because of high burden of 25000 PVCs on 24 h ECG registration and progressive deterioration of ejection fraction, despite antiarrhythmic drugs, catheter ablation was considered. An high density multielectrode mapping catheter was used and an initial right ventricular mapping was perfomed, recording local electrograms but without identification of a clear earliest site of activation. Therefore a retrograde transaortic left ventricular mapping was performed. Earliest site of activation was not significant (about 15 milliseconds), as well as percentage of correlation during pace–mapping. Epicardial mapping through coronary sinus into the anterior interventricular vein (AIV) showed a significant earliest activation site (greater than 30 ms) and a negative unipolar signal (QS) was detected. Pacing in this region highlighted a significant percentage of correlation with native PVC (92%), then catheter ablation was attempted. A first short duration application of radiofrequency was erogated on the endocardial side in front of the projection of the catheter in the AIV, because of possible risks of procedure, obtaining a temporary PVC suppression. Subsequently, after execution of a coronary angiogram proving a distance of the ablator in AIV and IVA/Cx vessels greater than > 1 cm, an endovenous approach was attempted with application of radiofrequency into the AIV, obtaing complete PVC suppression. At a 6 months follow–up ejection fraction improved (FE 50%) and PVC were not detected. Discussion Epicardial approach throught coronary sinus is an effective strategy to map and ablate arrhythmias of left ventricular summit. In addiction this stretegy allows a less invasive epicardial approach than other procedures, requiring a cardiosurgery standby.