Patent Ductus Arteriosus in Dogs

Patent Ductus Arteriosus in Dogs

By: PetPlace Veterinarians

Section: Veterinary Care In-depth

Veterinary care should include diagnostic tests and subsequent treatment recommendations.

Diagnosis In-depth

Diagnostic tests are needed to recognize PDA and exclude other diseases. A definitive diagnosis may require additional tests including chest X-rays, electrocardiogram and ultrasound examination of the heart (echocardiography or cardiac echo). It is important to exclude other congenital heart defects. Tests may include:

  • Examining the heart with a stethoscope and detecting a characteristic heart murmur

  • Chest X-rays (thoracic radiographs) can demonstrate the heart size and characteristic changes found in PDA. Heart failure can be diagnosed from this examination.

  • EKG is a supportive diagnostic test. It is less valuable than an echocardiogram, but is useful when an echo is not available.

  • Echocardiogram is an ultrasound test that can image the heart.
    Though difficult to see, experienced examiners can visualize the PDA. Furthermore, other heart birth defects can be excluded. Doppler studies are blood flow studies capable of definitely diagnosing the abnormal flow across the ductus. This is a referral examination done by a specialist in most cases.

  • Angiography (dye studies) is almost never done today.

  • Biochemistry may be tested with serum blood tests to determine general health and check for secondary conditions.

  • Routine blood tests may be performed prior to any anesthesia. In the rare case of right to left PDA, the complete blood count (CBC) may show an elevated packed cell volume (PCV).

    Treatment In-depth

    Treatments for PDA may include one or more of the following:

  • The conventional treatment is surgery done shortly after diagnosis. This involves general anesthesia and an incision in the chest (thoracic surgery). The PDA is isolated and closed with surgical suture. There is no benefit to delaying surgery. In fact, the chances of a dog developing heart failure or suffering irreversible damage to the heart muscle only increase with time. Operative success should be greater than 90 percent, even in the smallest dogs. Activity should be restricted until surgery is completed.

    One should NOT delay surgery waiting for symptoms to develop. This is a common mistake (thinking: "I'll have this fixed once we see some problems with our dog"). Anesthetic and surgical risks become greater as the heart fails and the heart muscle or lung arteries can become irreversibly damaged.

  • Medical treatment (furosemide, +/- digoxin) may be necessary before surgery if symptoms such as coughing or difficult breathing are present. These symptoms are typically caused by left-sided heart failure - the accumulation of fluid, or pulmonary edema, in the lungs.

  • Aspirin, indomethacin and other prostaglandin inhibitors sometimes used to close the PDA in premature human babies do NOT work in dogs and should not be given to close the ductus. The canine ductus lacks the smooth muscle capable of responding to these drug therapies. Furthermore, these are dangerous drugs in young pets, capable of causing kidney injury and stomach bleeding.

  • In some referral centers, the PDA may be closed using special catheterization techniques. Some of these procedures can be done without any incision at all (percutaneous PDA closure), but the techniques require special experience and equipment and are not widely available.

  • When surgery is not an option, and heart failure has occurred, drug therapy with furosemide, enalapril or benazepril and digoxin is often prescribed. A salt-restricted diet is enforced.

  • Dogs with polycythemia caused by right to left shunting PDA should be treated periodically by phlebotomy, which is removing blood to control the red blood count and viscosity of the blood. Surgery cannot be done in these pets.

     
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