Information on PDA

Article from: http://cvm.msu.edu/courses/AP/pda/treat.htm

What is Patent Ductus Arteriosus (PDA) ?

In the unborn puppy (fetus) blood does not pass through the lungs.
The mother dog does the breathing for the puppy and supplies all of the oxygen it needs.

The ductus arteriosus is a normal blood vessel in the fetus that connects the two main arteries of the body, the pulmonary artery and the aorta.. The pulmonary artery is the main blood vessel that carries blood from the body to the lungs. The aorta is the main blood vessel that carries blood from the heart to the rest of the body.

The ductus arteriosus allows blood to bypass the lungs. Since the lungs are not yet needed for breathing, the blood flows from the right side of the heart to the left through the ductus arteriosus.

When the puppy is born and begins to breathe on its own, the ductus arteriosus should close automatically. This usually occurs within one week after birth. This causes blood to flow into the lungs, where it picks up and distributes oxygen throughout the body.

In a dog with a patent (open) ductus arteriosus, the blood vessel doesn't close and blood ends up flowing in the wrong direction. Some blood is pumped back into the lungs instead of into the body. This can cause serious respiratory complications.

What Causes PDA

Patent ductus arteriosus (PDA) is the most common heart defect found in dogs.

It affects about 1 out of every 150 puppies.

The disorder is more common in female dogs than in males.

The disease is usually genetic, meaning it is passed on from one generation to the next. Affected dogs should not be bred because of the risk of passing the condition on to their puppies.

Some breeds that are at a higher risk include the Bichon Frise, Chihuahua, Cocker spaniel, Collie, English Springer spaniel, German shepherd, Irish setter, Keeshond, Kerry blue terrier, Maltese, miniature and toy Poodle, Pomeranian, Sheltie, and Yorkshire terrier

What are the effects of PDA

In dogs with a PDA, blood flows from the high-pressure aorta (left side) to the low-pressure pulmonary artery (right side).

This results in an increased volume of blood flowing to the lungs, which can lead to a build up of fluid in the lungs. This causes respiratory problems in the dog, such as decreased exercise ability and coughing. The heart has to work harder to pump blood, which may lead to heart failure.

How badly the dog is affected depends on how severe the defect is (how much blood is flowing through the PDA).

What Are The Clinical Signs?

In the beginning, the affected dog may show no clinical signs even if a murmur is heard.

If nothing is done, the dog will usually begin to show signs sometime within the first year of life.

As the dog grows older, the heart may become unable to keep up with the body's demands. The dog usually responds to this by limiting its activity, and therefore the amount of work done by the heart. Decreased activity is a common sign in dogs with a PDA.

Typical signs observed include difficulty breathing, coughing, inability to exercise for long periods of time, and sometimes even collapse while exercising. Affected dogs tend to be smaller than their littermates, usually play less and may grow at a slower rate

How is PDA Diagnosed?

Puppies that have a PDA are often diagnosed when they are brought to a veterinarian for their initial examination or for routine vaccinations.

The most common examination finding in a dog with a PDA is the presence of a characteristic continuous "machinery" heart murmur. A murmur is an abnormal heart sound that can be heard by the veterinarian using a stethoscope. A murmur is caused when blood flows in an abnormal pattern.

If a high volume of blood is flowing through the PDA, the murmur can be loud enough to hear without a stethoscope. The blood flow may even cause the dog's chest to vibrate, which is called a "thrill".

Additional tests are performed in patients suspected of having a PDA. These tests include radiographs (x-rays) of the chest, an electrocardiogram (ECG) and ultrasound of the heart.

How is PDA Treated?

The treatment of a patent ductus arteriosus (PDA) is surgery. The procedure involves making an incision into the chest, locating the ductus arteriosus and then tying it off with suture material. After the vessel is tied off, the blood begins to flow in the proper direction.

The surgery should be done as soon as possible after the diagnosis is made.

Surgery is highly recommended for qualified patients. Without immediate surgical intervention, more than half of the dogs diagnosed with a PDA will die in about one year.

If clinical signs such as difficulty breathing and coughing are already present, it may be necessary to hospitalize and stabilize the dog before going to surgery.

What is the Prognosis?

The prognosis for a dog with a patent ductus arteriosus (PDA) is very good if the surgery is performed early.

After a routine and successful surgery, the dog should be able to live a normal life.

Unless there are complications or other problems, it is usually not necessary for the dog to be on medication or have its activity restricted