11-month-old female intact Labrador Retriever

• An 11–month–old female intact Labrador Retriever was referred for abnormal cardiovascular blood flow.
• The patient had a history of megaesophagus secondary to a persistent right aortic arch (PRAA) that was surgically corrected at approximately 3 months of age. At the time of surgery, a persistent left cranial vena cava was noted.
• Five months after surgery, an echocardiogram was performed due to a heart murmur and showed abnormal flow in the main pulmonary artery raising concern for a Patent Ductus Arteriosus (PDA), despite the previous surgical correction for PRAA with presumed transection of the ligamentum arteriosum. The dog was referred to our cardiology section for further assessment.
• On presentation, a grade I-II/VI left-sided systolic heart murmur was appreciated, without arrhythmias or pulse deficits. The remainder of the physical exam was within normal limits. An echocardiogram showed left atrial and ventricular enlargement, and an area of abnormal continuous left-to-right blood flow in the distal pulmonary artery. The location was considered atypical for a PDA, especially given the history of reported ligation of the ligamentum arteriosum.
• The flow was therefore concerning for another type of anomalous systemic-to-pulmonary arterial shunt, and CT angiography of the thorax was scheduled.

• Enlarged left bronchoesophageal artery (LBEA1) arising from the aorta (abnormally right sided) at the level of T6 and enters the large group of anomalous vessels along the right of the esophagus.
•  Cranial to this enlarged bronchoesophageal artery, there is a large artery arising from the aorta at the level of T4-5 which travels cranially and to the left blending into another group of vessels left of the esophagus. This could represent a second left bronchoesophageal artery (LBEA2).
•  The right bronchoesophageal artery (RBEA) is enlarged and abnormally begins from the left side of the brachiocephalic trunk immediately after its origin from the aortic arch. It then continues caudally in a tortuous manner ventral to the trachea, and eventually feeds into a small cluster of vessels to the right of the trachea, in the area of the bifurcation of the main pulmonary artery.
•  The left pulmonary artery is larger than the right, indicative of abnormal systemic to pulmonary shunting into that artery.
•  The abnormal esophageal vasculature connects to the left pulmonary artery caudal to its origin, along the left ventral aspect of the esophagus.
•  Other vascular anomalies include:
  •  Persistent right aortic arch
  • Aberrant left subclavian artery, originating from the dorsal margin of the cranial most aspect of the descending aorta
  •  Persistent left cranial vena cava (in addition to a normal right cranial vena cava);
  • A left sided azygous vein emptying into the left cranial vena cava.
•  Esophageal dilation is present cranial to the heart base at the level of T2. It is narrower at the level of the origin of the left subclavian artery.
•  The lungs and pleural space are normal.

● Bronchoesophageal hypertrophy with arterial systemic-to-pulmonary fistula. This is most likely congenital (see discussion below). There are potentially two bronchoesophageal arteries with the smaller of the two more consistent with the typical origin of the left bronchoesophageal artery. The right bronchoesophageal artery also has an abnormal origin. These abnormalities explain the enlarged left pulmonary artery and left-to-right shunt diagnosed on echocardiogram.

● Multiple other vascular anomalies: persistent right aortic arch, aberrant left subclavian artery, left cranial vena cava, and left sided azygous vein.

● It cannot be determined which artery is the original anomalous connection due to the numerous small tortuous mediastinal vessels. Outcome: Multiple interventions were discussed and ultimately not recommended due to low probability of successful treatment. The patient continues to be actively monitored in the months following the CT scan.

Esophageal vascular varices are uncommon among the canine population and rarely directly cause presenting clinical signs, unlike humans1. Patients commonly have a left sided heart murmur of variable intensity, but are otherwise asymptomatic for systemic to pulmonary fistulas2. In a case series of 25 dogs with esophageal varices, 11 dogs’ anomalies occurred within the thorax, including 6 which involved bronchoesophageal vasculature1. Aberrant branches of the bronchoesophageal artery can resemble the flow pattern observed on echocardiography of a dog with a PDA, suggesting further imaging is necessary to distinguish these abnormalities3.

About half (6/11) of dogs with diagnosed bronchoesophageal artery hypertrophy and systemic to pulmonary fistulas had echocardiographic changes consistent with a PDA4. Dogs with this diagnosis have been split into two categories, congenital and acquired, based on distinct patterns found on Computed Tomography (CT) scans4.

Of the dogs with esophageal varices, the median survival time was 866 days for dogs who did not have underlying neoplasia and no animal was euthanized or died for complications secondary to their vascular anomaly1. The patient in this study was referred for advanced imaging due to previous congenital anomalies and suspicion for a Patent Ductus Arteriosus. She had a previous surgery to address a Persistent Right Aortic Arch (PRAA), during which a persistent left cranial vena cava and anomalous vessels of unknown origin were identified.

Ultimately, this dog was diagnosed with bronchoesophageal arterial hypertrophy with a systemic-to-pulmonary fistula consistent with the criteria for a congenital origin, along with multiple other congenital vascular abnormalities2. Advanced imaging such as CT Angiography was instrumental for a full understanding of the complex vascular anomalies at hand in this patient.

1. Slead TS, Gremillion CL, Cohen EB, Tolbert MK. Esophageal varices in dogs: A retrospective case series. J Vet Intern Med. 2022;36(2):493–499.

2. Ledda G, Caldin M, Mezzalira G, Bertolini G. Multidetector-row computed tomography patterns of bronchoesophageal artery hypertrophy and systemic-to-pulmonary fistula in dogs. Vet Radiol Ultrasound. 2015;56:347-358.

3. Yamane T, Awazu T, Fujii Y, Watanabe T, Muto M, Okutsu M, Wakao Y. Aberrant branch of the bronchoesophageal artery resembling patent ductus arteriosus in a dog. J Vet Med Sci. 2001;63:819-822.

4. Claretti M, Pradelli D, Borgonovo S, Boz E, Bussadori CM. Clinical, echocardiographic and advanced imaging characteristics of 13 dogs with systemic-to-pulmonary arteriovenous fistulas. J Vet Cardiol. 2018;20(6):415- 424.