Abnormal coronary artery origin Coronary ostial atresia 2017-12-16T16:26:05Z Absence of the normal opening of a coronary ostium. There are normally two coronary ostia, which are site of origin of the main left or right main coronary artery and are located in the ascending aorta just above the aortic valve. Atresia of coronary ostium Coronary ostial atresia is usually associated with ischemic manifestations