**7.1 Abnormal orifice**

The orifice is never circular with an ovoid or ellipsoidal shape. The area of the slit-like ostium is not necessary significantly reduced, like during selective coronary angiography. It is the fact that the longest diameter of the orifice may be as long as the diameter of the distal segment. Importantly, the IVUS shows a normal intima tunica without atherosclerotic plaque.
