Single coronary ostium - a right coronary artery arising from the left main coronary artery.

Single coronary ostium is a very rare congenital anomaly with an incidence of 0.024% in angiographic series. This is the third case of Shirani-Roberts subtype IB4: solitary ostium in the left coronary sinus associated with a retroaortic-coursing right coronary artery that arises from the left main coronary artery. The patient is a 45-year-old male with no past medical history, and who was seen in the clinic for evaluation of a murmur. Echocardiography showed rheumatic heart disease with mild mitral regurgitation and moderate aortic regurgitation; no shunts were present. Coronary and aortic root angiography did not show a vessel originating from the right coronary cusp. The right coronary artery originated from the left main coronary artery and had an aberrant course which was dorsal to the ascending aorta. No associated congenital heart disease was present.