Persistent right aortic arch is a congenital vascular abnormality which can cause regurgitation in young dogs. It occurs more frequently in German Shepherds than in other breeds.

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Normal thoracic anatomy

This postmortem specimen shows normal thoracic anatomy. The left- sided aorta, pulmonary artery, and ligamentum arteriosum are visible as are the right-sided trachea and esophagus below them.

praa2 Normal thoracic vascular anatomy. The aorta lies to the left of the esophagus and trachea (identified with ligatures).	praa2a The aortic arch and descending aorta highlighted in red.
praa2b-n The main pulmonary artery, highlighted in purple.	praa2c-n The ligamentum arteriosum, highlighted in green.
praa2d-n The trachea, highlighted in yellow	praa2e-n The esophagus, highlighted in white.

Anatomy of a persistent right aortic arch

This diagram shows the aorta coursing to the right of the esophagus and trachea, and the ligamentum arteriosum connecting the aorta to the pulmonary artery. A retroesophageal left subclavian artery is also shown crossing the dilated esophagus. The esophagus is dilated cranial to the heart and the main constriction is at the level of the ligamentum arteriosum.

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This post mortem specimen is from a dog with persistent right aortic arch and retroesophageal left subclavian artery (RLSA). Note the dilated esophagus cranial to the heart, and the ligamentum arteriosum connecting the aorta on the right side of the esophagus to the pulmonary artery on the left side. Corrective surgery will involve isolation of the ligamentum and division between ligatures to relieve the constriction on the esophagus. The RLSA also is divided between ligatures close to the aorta. Collateral circulation to the foreleg is supplied by retrograde flow through the vertebral artery.

praa4b-n Post-mortem view of a dog with a persistent right aortic arch and a retroesophageal left subclavian artery.	praa4a-n Retroesophageal left subclavian artery, higlihgted in orange.
praa4c-n Ligamentum arteriosum, highlighted in green.	praa4d-n Descending aorta, highlighted in red, lying to the right of the esophagus.
praa4e-n Main pulmonary artery and left caudal lobar artery, highlighted in purple.