+ 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
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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. With the normal arrangement of the major arteries of the heart (aorta and pulmonary artery), the aorta is to the left of the esophagus and the trachea is just beneath the esophagus at the level of the base of the heart. The pulmonary artery is also on the left and just below the aorta. The ligament (ligamentous arteriosum) that is the remnant of the patent ductus arteriosus, a vessel that connects the aorta to the pulmonary artery in the fetus. As a result, the ligamentum arteriosum does not contstrict the esophagus (see cross-sectional CT image, Normal).
In the patient with a PRAA, the right aortic arch develops into the aorta (called a dexter aorta). Over the base of the heart, the esophagus is entrapped by the trachea on the right (T), aorta on top and right, pulmonary artery on the left and a the ligamentous arteriosum that extends from the pulmonary artery (vessel that pumps blood to the lungs) and the aorta (see cross-sectional CT image, PRAA; take note that the right side of the patient is on the left side in the image).
In 95% of the cases of a vascular ring anomaly, a persistent right aortic arch is present. However, other vascular anomalies such as an aberrant subclavian artery or a double aortic arch may be the cause of the esophageal constriction.
Regardless of the type of vascular anomaly, the constriction prevents solid foods from passing to the stomach and prevents the puppy from thriving well.
Breeds commonly affected include the Great Danes, German Shepherds and Irish setters. Clinical signs are seen when solid food is introduced and 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 are deprived of nutrition.
A presumptive diagnosis of a PRAA is made from radiographs (x-rays) made after a barium swallow. The esophagus in front of the heart will appear dilated (see radiograph right). 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 due to poor intake of food 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. CT scan is an excellent diagnostic modality to evaluate a patient suspected to have PRAA. About 50% of the dogs sent to us with a presumptive diagnosis of PRAA, do not have this condition, rather have generalized megaesophagus. CT scan is more definitive diagnostic modality to evaluate the lungs for pneumonia. During the CT scan, the esophagus is inflated with air and intravenous contrast is administered to the patient to outline the vascular structures. The scan will define the specific type of vascular ring anomaly, which will help the surgeon make a surgical plan to treat the constriction of the esophagus.
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 to ensure that the food will pass into the stomach by means of gravity. A baby Bijourn can be used to keep the puppy upright to encourage the food to pass into the stomach or the puppy may be held upright. Another creative method of feeding the puppy is to put a "onesie” on the puppy and then suspend the puppy as shown below. Careful monitoring of the puppy is essential with this method, as a "set it and forget it" approach could potentially be dangerous. In order to encourage the puppy to remain in an upright position, a teaser food that the puppy can lick (see puppy licking peanut butter off the orange rope below). Finally a Bailey's chair may be used to keep the puppy upright. This is generally safe and requires less supervision.
If pneumonia is present it must be treated before the surgery 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. Watch videos below for surgical anatomy.
The constricting band is isolated using a surgical instrument (see photo right), tied with suture and cut. The constricting band must be tied off, as the ligamentum arteriosum may be a patent blood vessel in very young animals. After the constricting band is cut, additional fibrous tissue that may be constricting the esophagus is dissected off the esophagus. A tube is placed down the mouth and through the esophagus to ensure that there are no additional constrictions.
After surgery, medication is given to your puppy to ensure a relatively 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.
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.
Overall, about 80% 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.
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