Persistent Right Aortic Arch


Key Points

PRAA is a congenital anomalie of the blood vessels of the heart that results in constriction of the esophagus

Surgery is the best treatment option

Treatment early is better for the patient

Prognosis is very good

 

Introduction

  • During development in the uterus, the fetus has a right and left aortic arch. Normally the left aortic arch forms the main artery that extends off the heart and travels to the abdominal region. If the right aortic arch develops into the aorta, the esophagus becomes trapped by a ligament that extends from the pulmonary artery (vessel that pumps blood to the lungs) and the aorta.
  • In 95% of the cases of a vascular ring anomalie, a constricting band prevents solid foods from passing to the stomach which prevents the puppy from thriving well. In the remaining 5% of cases a bizarre anomalie of the vessels is present (double aortic arch and aberrant subclavian artery), which may be difficult to correct and may not have a good prognosis.

 

Clinical signs

  • Breeds more commonly affected include the Great Dane, German Shepherd, and Irish setter. Although other breeds can also be affected.
  • Clinical signs commonly are present when the puppy is very young. Usually signs are not seen until solid food is fed, at the time of weaning off the mother’s milk.
  • Signs include regurgitation of food or fluid, unthriftiness, stunted growth, and signs related to pneumonia (lethargy, coughing, breathing difficulty). These puppies usually have hearty appetites, because they cannot get the nutrition that they need.

Diagnosis

  • The diagnosis of a PRAA is generally made from radiographs (x-rays) made after a barium swallow. The esophagus in front of the heart will appear dilated. In some cases the esophagus behind the heart will also be dilated. This is a warning sign that the puppy could have poor function of the esophagus even if surgery is performed.
  • Radiographs are also used to determine if the puppy has concurrent pneumonia.
  • Blood testing including a complete blood count, chemistry profile and urinalysis are recommended to make sure that the puppy has healthy internal organs prior to surgery and may show signs of low blood sugar or a high white blood cell count if infection is present.
  • An ultrasound may also be recommended to rule out other congenital heart defects that may require attention.

Treatment

  • Prior to surgery it is important to provide as much nutrition as possible to the puppy. This may include feeding a high calorie gruel. During and after feeding a meal, the puppy’s front end should be elevated so as to make sure that the food will pass into the stomach by means of gravity.
  • If pneumonia is present it must be treated with antibiotics, nebulization, and coupaging the chest to bring up phlegm.
  • On the day of surgery an intravenous catheter will be placed to provide intravenous fluid therapy. Young puppies are also very susceptible to developing low blood sugar, therefore a sugar solution is typically incorporated in the intravenous fluids.
  • An incision is made on the left side of the chest and the fourth and fifth ribs are spread to expose the band (ligamentum arteriosum) constricting the esophagus. The band is readily identified by running a finger or the tip of a surgical instrument along the esophagus. The phrenic, vagus and recurrent laryngeal nerves, located near the constricting band are identified and protected during the procedure.
  • The constricting band is isolated using a surgical instrument, tied twice with suture and cut. The constricting band must be tied off, as the ligamentum arteriosum frequently still is a patent vessel in very young animals. After the constricting band is cut, fibrous tissue that may be constricting the esophagus is dissected off the esophagus. A tube is placed down the mouth and through the area of the esophagus to make sure that there are no additional constrictions.
  • After surgery, medication is given to your puppy to ensure a pain-free recovery. Intravenous fluids are administered at least over night or longer if indicated. Once the puppy is eating and drinking well, intravenous fluids may be discontinued.
  • Your puppy may have a chest tube after surgery, which is used to remove fluid and air from the chest cavity. Typically, the tube can be removed after 12 to 24 hours. Some surgeons prefer to administer pain relieving medication (local anesthetic) through the tube to numb the incision.
  • Elevated feedings may be required for an additional month after surgery. If the puppy is no longer regurgitating, the elevated feedings can be discontinued. Once the puppy can swallow well and there is no regurgitation, solid foods can be gradually introduced.
  • Exercise must be restricted for 3 weeks after surgery so that the surgical site can heal properly

Complications

  • In spite of performing the corrective surgery, some puppies never regain normal motility of the esophagus and the puppy will remain unthrifty and likely will die.
  • Pneumonia is a possible problem due to aspiration of fluid that may pool in the esophagus.
  • Infection of the surgical site is possible, but an infrequent complication.
  • It has been shown that puppies less than 2 months of age have a much higher death rate due to anesthesia and surgery. Yet, the surgery should not be delayed too long, as permanent damage to the esophagus may occur.

Prognosis

  • Overall, about 90% of dogs having surgery to correct this condition will have resolution of the regurgitation and they thrive well. The remaining dogs may do poorly or may may be improved from the preoperative condition.

References

  1. Muldoon MM, Birchard SJ, Ellison GW. Long-term results of surgical correction of persistent right aortic arch in dogs: 25 cases (1980-1995). J Am Vet Med Assoc 1997;210(12):1761-3.
  2. Vianna ML, Krahwinkel DJ. Double aortic arch in a dog. J Am Vet Med Assoc 2004;225:1222-1224.
  3. Holt D, Heldmann E, Michel K and Buchanan JW. Esophageal obstruction caused by a left aortic arch and an anomalous right patent ductus arteriosus in two german shepherd littermates. Vet Surg 2000;29:264-270.
  4. Gunby JM, Hardie RJ, Bjorling DE. Investigation of the potential heritability of PRAA in Greyhounds. J Am Vet Med Assoc 2004;224: 1120- 1122.
  5. Koc Y, Turgut K, Alkan F, Birdane FM. Persistent right aortic arch and its surgical correction in a dog. Turk J Vet Anim Sc 2004;28:441-446.
  6. MacPhail CM, Monnet E, Twedt DC. Thorascopic correction of persistent right aortic arch in a dog. J Am Anim Hosp Assoc 2001; 37:577-581.
  7. Isakow K, Fowler JD, Walsh P. Video assisted thorascopic division of the ligamentum arteriosum in two dogs with PRAA. J Am Vet Med Assoc 2000;217: 1333-1336.

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