Patent ductus arteriosus (PDA) is a congenital heart defect in dogs, which means that the problem develops in the womb and is present at birth. To appreciate the effects that a PDA has on a dog’s body it’s essential to understand puppy development and some basic anatomy.
Dog Heart Anatomy and Development
In healthy dogs, deoxygenated blood returns from the body to the right side of the heart. Next, this blood goes to the lungs through the pulmonary artery to be reoxygenated, and then it travels back to the left side of the heart. The aorta is the main artery that feeds this oxygenated blood from the left side of the heart to the rest of the body.
In the womb, the fetal aorta is connected to the pulmonary artery by a special blood vessel called the ductus arteriosus. This vessel allows blood to flow directly from the right side of the heart to the aorta, bypassing the lungs. This works in the womb because the fetus gets its oxygen from the mother's bloodstream through the placenta, not through its own lungs.
Normally at birth, this connection is no longer patent (open). Once a newborn has begun to breathe on its own, the ductus arteriosus closes and the pulmonary artery opens so blood can flow from the right side of the heart into the lungs to be oxygenated. But with a patent ductus arteriosis, the connection remains open. Consequently, blood moves in abnormal ways through the heart and lungs. A PDA allows blood to flow directly from the aorta into the pulmonary artery, and then to the lungs. This is called a shunt.
If the shunt is moderate to large, it can cause left-sided congestive heart failure from blood volume overload on the left side of the heart. Less frequently, a large PDA will cause injury to the blood vessels in the lungs because an excessive amount of blood is flowing through them. High blood pressure in the lungs can cause a reversal of the shunt so the blood goes from right to left (pulmonary artery to the aorta).
This atypical right-to-left shunting of a PDA can cause the aorta to carry blood that is low in oxygen to the rest of the body, causing problems including the production of extra red blood cells (since they carry oxygen), making the blood too thick.
Symptoms and Types
The symptoms associated with patent ductus arteriosus in dogs depend on the severity of the abnormality and how long it has been present. In general, some combination of the following is noticeable early in an affected dog’s life:
- Heart murmur
- Exercise intolerance
- Poor growth
Left-to-right shunting PDA:
- Rapid breathing
- Difficulty breathing
Right-to-left shunting PDA:
- Hind legs are weak
- Blue-tinged gums and skin
Causes of Patent Ductus Arteriosus in Dogs
Genetics is the primary risk factor for PDA in dogs. Purebred, female dogs are at increased risk. Popular breeds that are predisposed to PDA include:
- American cocker spaniel
- Bichon frise
- English springer spaniel
- German shepherd dog
- Irish setter
- Kerry blue terrier
- Labrador retriever
- Shetland sheepdog
- Yorkshire terrier
Diagnosis of Patent Ductus Arteriosus in Dogs
Your veterinarian will perform a thorough physical exam on your dog, likely followed by a chemical blood profile, a complete blood count, and a urinalysis to provide general health information. You will need to give a thorough history of your pet's health leading up to the onset of symptoms.
Visualization of the heart, using radiographs (x-rays) and ultrasound, is necessary for an accurate diagnosis of PDA and to plan appropriate treatment.
Treatment of Patent Ductus Arteriosus in Dogs
With left to right PDAs, surgery will be needed to place a device that will gradually close the abnormal connection between the aorta and pulmonary artery. Before surgery, a dog’s condition may need to be stabilized using oxygen therapy and medications. It is safe to perform this operation on puppies as young as seven to eight weeks of age. Surgery is not without risks, but many dogs respond beautifully.
Pets with a right to left shunting PDA cannot have a surgical correction. Their condition will sometimes respond to medical management for a period of time, but most eventually die as a result of their PDA.
Living with Patent Ductus Arteriosus
Dogs with a mild to moderate, left to right PDA can be treated normally after they have been allowed several weeks to recover from their surgical correction. Your dog’s surgeon will provide you with individualized recommendations for postoperative care and monitoring.
Preventing Patent Ductus Arteriosus
Because this trait is genetically transmitted, dogs that have had a PDA should not be bred.
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