Schematic showing anatomic locations of accessory pathways as they cross the AV junction

The atrioventricular (AV) valve plane of the heart is viewed from the cardiac apex. The tricuspid valve is on the left in this figure and the mitral valve on the right; the coronary sinus, which provides the venous drainage of the heart, passes posterior to the mitral valve and empties into the right atrium above the tricuspid valve. All AV bypass tracts cross the AV valve plane; their locations are named with respect to this orientation (eg, an anteroseptal bypass tract crosses the AV valve plane from atrium to ventricle in the region marked "anteroseptal" in the figure, at approximately 10 to 11 o'clock with respect to the mitral valve ring).