Persistent Right 4th Aortic Arch

James Montgomery, DVMDecember 8, 2008

Acc # 98847

• Barley– Referred for vascular

ring anomaly

• 3 months old

• Male

• Mixed breed

Acc # 98847

• CT (acc # 98848) confirmed right-sided aortic arch

• Also has left retroesophageal subclavian artery

Persistent Right 4th Aortic Arch (PRAA)

• The best documented vascular ring anomaly in dogs and cats (approx. 95% of ring anomalies are PRAA)

• Considered to have a familial tendency• Other, less common vascular anomalies include:– Persistent right or left subclavian arteries– Double aortic arch– Persistent right dorsal aorta– Left aortic arch and right ligamentum arteriosum– Aberrant intercostal arteries

PRAA Signalment

• Puppies and kittens at time of weaning

• German shepherds, Labrador retrievers, and Irish setters appear predisposed

• Male and female fairly equally represented

PRAA Clinical Signs

• Regurgitation of solid foods at weaning

• Weight loss with failure to thrive despite a good appetite

• Moist cough, dyspnea, fever – aspiration pneumonia common

Diagnostics• Survey thoracic radiographs– Esophageal body dilation cranial to the heart base

• Barium esophagram– Confirm location of esophageal obstruction and

severity of esophageal distension• Angiography– Confirm type and location of vascular anomaly prior

to surgery• Esophagoscopy– Differentiate intraluminal stricture from extraluminal

compression

Radiographic Findings• VD or DV radiographs

– Trachea curving to the left rather than the right near the cranial border of the heart

• Lateral radiographs– Ventral curvature of the

trachea• Marked ventral curvature

should prompt a thorough search for additional abnormalities– Retroesophageal left

subclavian artery, double aortic arch

– Focal narrowing of the trachea cranial to the heart

Differentials

• Vascular ring anomalies should be differentiated from:

– Congenital idiopathic megaesophagus

– Esophageal foreign body

– Cricopharyngeal dysphagia

PRAA• Congenital defect in development of the aortic

arches• Right 4th aortic arch develops into the aorta

rather than the Left 4th aortic arch• Results in esophagus passing to the left of the

aorta instead of the right• Esophagus ringed by:– Aorta– Ligamentum arteriosum– Pulmonary trunk– Base of heart

PRAA

Buchanan, JVIM 2004

Embryology

• Two 3rd aortic arches give rise to the common carotid arteries

• Left 4th aortic arch becomes the aorta

• 6th aortic arch gives rise to the pulmonary trunk and pulmonary arteries

Associated Vascular Anomalies

• Buchanan, JVIM 2004– 52 dogs with PRAA• 17 (33%) also had retroesophageal left subclavian

artery• 6 had PDA• 6 had double aortic arches with atretic left arch• 6 had persistent left cranial vena cava• 3 had a left hemiazygos vein

– 2 had PRAA and generalized megaesophagus

Treatment

• Surgical ligation and transection of the ligamentum arteriosum– If atretic left aortic arch is present, must transect this

as well to relieve esophageal obstruction

• Treatment of aspiration pneumonia (if present)

• If not diagnosed early, progressive esophageal dilation causes irreversible myenteric nerve degeneration and esophageal hypomotility.

References

• Buchanan JW. Tracheal Signs and Associated Vascular Anomalies in Dogs with Persistent Right Aortic Arch. J Vet Intern Med 2004; 18:510-4.

• Jergens AE. Diseases of the Esophagus. In Ettinger SJ, Feldman EC, eds. Textbook of Veterinary Internal Medicine, 6th ed (St. Louis, MO: Elsevier Saunders, 2005) pp. 1306-7.

• Pasquini C, et al. Anatomy of Domestic Animals, 9th ed (Pilot Point, TX: Sudz Publishing, 1997) pp. 390-2.