Fig. 1

Classification scheme for aortic arch anomalies leading to a vascular ring. All types can potentially cause esophageal compression. Esophageal compression is less likely in Type 2 and 6. Legend: (0) normal anatomy of the aortic arch; (1) Type 1, persistent right aortic arch with left ligamentum arteriosum; (2) Type 2, persistent right aortic arch with  persistent left subclavian artery; (3) Type 3, persistent right aortic arch with left ligamentum arteriosum and left subclavian artery; (4) Type 4, double aortic arch; (5) Type 5, normal left aortic arch with right ligamentum arteriosum; (6) Type 6 normal left aortic arch with persistent right subclavian artery; (7) Type 7, normal left aortic arch with persistent right ligamentum arteriosum and right subclavian artery; (8) Type 8, right aortic arch with left subclavian branching from the PDA; (9) Type 9, right sided aortic arch with left-sided brachiocephalic trunk including both carotid arteries and the left subclavian artery referred to as “mirror” image. The blue region represents the pulmonary arteries and the black region the ligamentum arteriosum. Type 1 to 7 previously described by Ellison G. Vascular Ring Anomalies in the dog and cat. Compendium on Continuing Education for the Practicing Veterinarian -North American Edition-. 1980;2:693–705