Figure 2 A:Surface electrocardiogram (ECG) after the ethanol infusion to the vein of Marshall (VOM). B: Intracardiac ECG after the ethanol infusion to VOM. Arrows indicate P waves. Note that P waves preceded atrial potentials in the LAA, and ventricular potentials preceded atrial potentials in the CS. C: Intracardiac ECG after the restoration of atrioventricular conduction. CS, coronary sinus; LAA, left atrial appendage.