Persistent Right 4 th Aortic Arch
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Persistent Right 4th Aortic Arch
James Montgomery, DVMDecember 8, 2008
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Acc # 98847
• Barley– Referred for vascular
ring anomaly
• 3 months old
• Male
• Mixed breed
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Acc # 98847
• CT (acc # 98848) confirmed right-sided aortic arch
• Also has left retroesophageal subclavian artery
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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
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PRAA Signalment
• Puppies and kittens at time of weaning
• German shepherds, Labrador retrievers, and Irish setters appear predisposed
• Male and female fairly equally represented
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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
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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
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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
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Differentials
• Vascular ring anomalies should be differentiated from:
– Congenital idiopathic megaesophagus
– Esophageal foreign body
– Cricopharyngeal dysphagia
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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
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PRAA
Buchanan, JVIM 2004
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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
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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
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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.
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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.