Variations in Sites of Origin of the Coronary Arteries

The ascending Ao may be divided into two parts, the sinus, or proximal, portion, and the tubular, or distal, portion. The junction between these two parts lies at about the level of the free edge of the aortic cusps. Deviation of a few millimeters in the level of origin of the coronary arteries with respect to the junction is common. When the origin is as much as 1 cm above the junction, a condition of congenital high takeoff or ectopic origin should be considered. Instances of congenital high takeoff of a coronary artery usually involve the RC. Variations within the normal range are shown in Figure 124, after which cases exhibiting high takeoff will be illustrated.