The Origin of the Coronary Arteries

Abstract

When a student examines the origin of the coronary arteries, three important features emerge: I. The left main branch has wide variations in its spatial disposition: In a horizontal plane, the axis may be anterior, transverse, or posterior: In a frontal plane, the axis may be superior, horizontal, or inferior. In any anatomic study, be it in a laboratory or a clinical setting, it is essential that both axes be defined. What is the clinical relevance of these axes? First, and most evident, they dictate the radiographic plane for the optimal examination of this vessel in which severe occlusive disease is not only common but life endangering—emergency bypass surgery is carried out in many centers. The second and conceivably more fundamental effect of these axes relates to the design of the coronary artery orifice—the axes are the major determinant of this design. II. The right coronary artery displays a characteristic proximal segment—it is 1.5 cm in length—which extends in a perpendicular manner from the right aortic sinus—a smooth orifice results. The left main branch, conversely, as a resultant of extremes in either of the two axes—and these extremes are not uncommon—may display a knife-like incisura at the inferior or one of its lateral margins.