Low voltage areas.

35 years old female (patient 48) showing abnormal electrograms at ablation site despite apparent absence of structural heart disease. (A) Cardiac magnetic resonance steady-state free-procession (SSFP) cine imaging in the in-out view of the right ventricle in diastole (A1) and systole (A2) showing no abnormalities. (B) Electroanatomical voltage map in sinus rhythm. The black line indicates the pulmonary valve. The voltage map showing a wide area of low voltage below the pulmonary valve. The color map of voltage signals is explained in the methods. Purple indicates normal tissue while red indicates scar. Decapolar catheter in the coronary sinus and the His bundle catheter are displayed in white and red, respectively, at the bottom of the figure. The ablation catheter at the ablation site is indicated by the white arrow head. One RF ablation at this site caused the disappearance of the PVCs, indicated by the red dots. (C) The bipolar electrogram on the ablation catheter (MAPd) at successful ablation site exhibits very low voltage electrograms and dull diastolic potentials (black arrow heads) in sinus rhythm preceding the QRS by -20 ms during the PVC.