Congenital ostial atresia of right coronary artery: an exceedingly rare anomaly diagnosed on CT angiography

Volume-rendered CT angiography images (A and B) depict the course of the tortuous collateral, traversing anterior to the right ventricular outflow tract and reaching the right atrioventricular groove. Absence of an ostial stump and presence of only one or two full-calibre connecting collaterals (without evidence of any narrowing at the transition between the supplying and the receiving vessel) is suggestive of its congenital origin, in contrast to the rich network of collateral vessels seen in cases of acquired RCA occlusions.1 Also in acquired occlusions, CTA can visualise the wall of the occluded segment and thus help rule out coronary ostial atresia. The major collateral pathways at the conotruncal level providing circulation between the right and left coronary systems include the preconal Vieussens’ ring, retroconal anastomotic ring in the interarterial space or the retroaortic Kugel’s ring.2 ‘Vieussens' arterial ring, thought to be a remnant of the embryonic conotruncal circle that gives rise to the coronary ostia, is a crucial intercoronary collateral connection between the conal branches of RCA and LAD artery, providing flow to either arteries in presence of congenital atresia or event of acquired stenosis/occlusion.