Patent ductus arteriosus is a common congenital heart problem often diagnosed in young dogs. The ductus arteriosus, a blood vessel present in unborn animals, normally closes at the time of birth. During embryonic development, this blood vessel carries oxygen-rich blood from the mother to the fetus, bypassing the young animal's lungs. 

At birth, the young animal begins to breathe and oxygen is obtained by the lungs. The ductus arteriosus closes and normal circulation is established. The problem occurs when the ductus arteriosus does not close. 

PDA is commonly diagnosed in animals less than one year old. Small, young animals can often tolerate this congenital defect for long periods of time. Depending upon the severity of the problem, and the age and size of the dog, heart failure may develop suddenly or not at all. 

PDA is often diagnosed during routine puppy vaccinations. A heart murmur, combined with a strong arterial pulse, alerts the veterinarian to the possibility of the disease. 

If PDA is suspected, additional diagnostic tests are necessary. Electrocardiography (ECG), x-rays, and / or echocardiography (cardiac ultrasound) are indicated in order to obtain an accurate diagnosis. 

Surgical correction of PDA is possible. When the surgery is performed by a veterinary cardiac surgeon, the prognosis is usually excellent. Without surgery, 60% of affected puppies die within one year after diagnosis. 

If surgery is a consideration, it must be done at a very early age. Your veterinarian can recommend a surgeon (or a major referral hospital) who is qualified in cardiac surgery. 

Cutting Edge Technique Cures K-9 Heart Defect

Dogs may have a leg up when it comes to congenital heart problems, especially if they live near the University of Illinois College of Veterinary Medicine in Urbana. There, veterinary cardiologists have been trained to repair congenital heart defects in dogs using a newly developed procedure that is concurrently still being evaluated in clinical trials for human use.
"Right now, we are the only veterinary school and evaluating this new repair technique in dogs," says veterinary cardiologist Dr. David Sisson. 

The way the heart develops in human babies and puppies is amazingly similar, so it isn't too surprising that the same congenital heart defects occur in both species. Patent ductus arteriosus, or PDA, is the most common congenital heart defect among dogs. 

Before birth, a passageway called the ductus arteriosus allows the blood that is ejected by the heart to bypass the developing pup's non-functioning lungs. Shortly after birth the ductus arteriosus should close, thus separating the blood pumped to the lungs by the right side of the heart from the blood that is pumped to the rest of the body by the left side of the heart. 

"Patent" is a medical term that means open; and the presence of a patent ductus arteriosus after birth simply indicates that this blood vessel did not close as it should have. The result is a connecting vessel that allows blood to travel in a circular fashion from the left side of heart through the lungs and immediately back to the left side of the heart. The heart must work much harder to maintain a normal amount of blood flow to the rest of the body. This extra workload eventually causes the heart to fail. 

"Most dogs with PDA will go into congestive heart failure before they are two years old," says Dr. Sisson. The first signs an owner might notice include a cough, rapid breathing, or difficulty breathing, especially with exercise. This heart defect is inherited in most affected dogs, and some of the breeds prone to developing PDA include the Toy and Standard Poodle, Collie, Pomeranian, Maltese, Shetland Sheepdog, German Shepherd, Yorkshire Terrier, and English Springer Spaniel. 

Luckily, a PDA can now be fixed with a relatively simple procedure that physically blocks off the PDA using a device inserted through a catheter placed in a large vein. "For the past fifty years, open heart surgery has been the only reliable way to repair a PDA," says Dr. Sisson. "Nonsurgical repair is cheaper, less invasive, and has fewer overall complications than surgical repair, and it has a comparable success rate." 

One device used to repair a PDA is a small spring-like coil that blocks off blood flow through the PDA. "The biggest problem with coils is the potential for the coil to slip out of place. When this happens the coil must be retrieved and the PDA closed in some other way," says Dr. Sisson. 

The device Dr. Sisson is evaluating is called an Amplatzer duct occluder. It is a space-age looking mushroom-shaped plug designed to fit snugly in the PDA, reducing the chance of slippage. It is filled with fibers that induce a clot to form, effectively blocking blood flow through the PDA. Using this device, Dr. Sisson has had a very good success rate so far, and he is continuing to evaluate its long-term performance. 

Because it is a procedure designed for use in human infants with congenital heart problems, Dr. Sisson was trained to do the surgery on dogs by a pediatric cardiologist. Since then, clients have come to the University of Illinois Veterinary Teaching Hospital from around the country for this still experimental procedure. "One woman drove with her dog from Georgia after two failed attempts to repair his PDA. Fortunately, we were able to repair his heart in a 45 minute long procedure," says Dr. Sisson. 

"This is one area where veterinary medicine has kept pace with human medicine," says Dr. Sisson. Though it can be a life-threatening problem if not caught early, PDA can be repaired quickly and safely in most affected dogs. For more information on PDA, contact your local small animal veterinarian. 

By Carrie Gustavson
Information Specialist
University of Illinois
College of Veterinary Medicine


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