Figure 3 The activation maps of the left atrium (A ) and right atrium (B ). Electrical propagation is indicated by yellow arrows. An incomplete block line (white line) was observed at both sides of the interatrial septum, and a narrow isthmus was located at its annular end. The schema of the electrical activation in the atria before (C ) and after (D ) the ethanol infusion to the vein of Marshall (VOM). A gray area indicates a slow conduction area. AVN, atrioventricular node; BB, Bachman bundle; CS, coronary sinus; CTI, cavotricuspid isthmus; FO, fossa ovalis; IVC, inferior vena cava; LAA, left atrial appendage. LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; MA, mitral annulus; MI, mitral isthmus; RAA, right atrial appendage; RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein; SN, sinus node; SVC, superior vena cava; TA, tricuspid annulus.