Figure 19a. Preoperative evaluation of a 53-year-man with chest pain. Coronary catheterization showed stenosis of the right coronary artery and findings consistent with an aberrant left coronary artery, which originated from the right coronary cusp. CT was requested to evaluate the anatomic course of the left coronary artery. (a) Axial curved MPR image shows the left coronary artery originating from the right coronary artery orifice (arrow), with passage of the left coronary artery between the pulmonary artery and aorta. (b) Sagittal volume-rendered image shows the relationship of the left coronary artery as it passes between the aortic root and pulmonary artery. Given this anomalous course, the cardiac surgeon used a LIMA graft to the distal left main coronary artery to bypass the anatomic site of narrowing.