Patent Ductus Arteriosus (PDA) in Dogs


Overview of Patent Ductus Arteriosus (PDA) in Dogs

The ductus arteriosus is a blood vessel that connects the two main arteries of the body – the aorta and the pulmonary artery. This blood vessel is normal in the fetus, but shortly after birth, it should close. When the ductus arteriosus remains open or patent after birth, this abnormal communication between the aorta and pulmonary artery passes extra volumes of blood into the lungs.

Patent ductus arteriosis (PDA) is a birth defect representing the second most common congenital heart defect of dogs. Approximately seven out of 1000 live birth puppies are affected.

Generally, there are no serious symptoms of PDA unless congestive heart failure has caused fluid buildup in the lungs. The condition is typically identified in puppies during a routine veterinary visit for vaccinations. Continual blood flow through the PDA into the lungs produces a continuous (machinery) heart murmur.

Even when the veterinarian identifies a PDA, most people believe their dog is normal. In some cases, the dog can be smaller than littermates or play less vigorously. However, the situation can be very misleading as symptoms usually occur within a year of diagnosis. If untreated, about 60 percent of affected dogs die within a year of diagnosis.

When caught early, and following treatment with successful closure of the PDA, most dogs live a normal life. Unless there are complications from other heart defects or heart failure has already developed, there is rarely any future need for medication. While special circumstances can influence the prognosis, most cases are straightforward.

PDA is genetically determined in almost every case, and this fact impacts the value of purebred dogs used for breeding. PDA is common in the miniature poodle, collie, Maltese, Shetland sheepdog, German shepherd dog, cocker spaniel, Pomeranian, and Labrador retriever. Female dogs are predisposed.

What to Watch For

  • Breathing difficulties
  • Coughing
  • Exercise intolerance
  • Lethargy
  • Diagnosis of Canine Patent Ductus Arteriosus 

    Various diagnostic tests are needed to recognize PDA, and exclude other diseases. Some of the necessary tests may include:

  • Complete medical history and physical examination including auscultation (stethoscope examination) of the heart and lungs. The heart murmur of PDA is characteristic and most experienced veterinarians learn to make the diagnosis simply by listening. Since other birth defects can also cause heart murmurs, a veterinary cardiologist may be consulted if the diagnosis is in doubt.
  • A chest X-ray (radiograph) can help determine the severity of the problem.
  • An electrocardiogram (EKG) can assist with the diagnosis.
  • An echocardiogram with Doppler (cardiac ultrasound) is the definitive diagnostic test. This may require referral.
  • Routine blood tests may be performed prior to any anesthesia.
  • Treatment of Canine Patent Ductus Arteriosus (PDA)

  • The conventional treatment is an operation done shortly after diagnosis. The PDA is closed with surgical suture.
  • Aspirin, indomethacin and other prostaglandin inhibitors do NOT work in dogs and should not be given to close the ductus – these are dangerous drugs in young pets.
  • Surgery should not be delayed by waiting for symptoms to develop.
  • Medical treatment may be necessary before surgery if symptoms (coughing, difficult breathing) are present.
  • In some referral centers, the PDA may be closed using special catheterization techniques.
  • Home Care and Prevention

    Before any surgery, provide only the exercise your dog can tolerate. Do not allow your dog to become short of breath with activity.

    Follow up with your veterinarian after surgery or surgical closure. In most cases, only a suture removal is needed and further follow-up is unnecessary.

    There is no way to prevent PDA but dogs diagnosed should not be bred, even if the defect has been corrected.

    In-depth Information on Patent Ductus Arteriosus (PDA) in Dogs

    Patent ductus arteriosus (PDA) is a common birth defect. The pressure in the aorta is higher than the pressure in the pulmonary artery, therefore, blood crosses the ductus from left (aorta) to right (pulmonary artery). Very infrequently, the increased blood flowing into the lungs injures the pulmonary blood vessels. This can reverse the path of blood flow from right to left. In this case, unoxygenated blood flows into the aorta to the rear limbs, causing weakness and complications such as an elevated red blood cell count (polycythemia), which makes the blood thick. Symptoms are usually precipitated by exercise and include weakness and even seizures.

    There are a number of reasons for heart murmurs in puppies. These conditions require different management and include:

  • Anemia and fever can lead to soft to moderate intensity murmurs.
  • Ventricular septal defect, a “hole in the heart” between the two ventricles, is common.
  • Aortic stenosis (or subaortic stenosis) is the most common heart defect in dogs today. This is a narrowing of the outlet from the left ventricle and obstructs blood flowing into the aorta.
  • Pulmonic stenosis is similar to aortic stenosis but affects the other side of the heart.
  • Innocent murmurs (not pathologic) are common in growing puppies. These sound different from PDA to the experienced examiner. Furthermore, these murmurs become softer and most always go away by the time of the rabies vaccine, which is usually given between four and 6 months of age.

    There are also many causes of stunted growth and of shortness of breath. Your veterinarian should investigate these symptoms.

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