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American Maltese Association

A National Breed and Member club of the American Kennel Club

Patent Ductus Arteriosus - PDA

Written by: 
Cheryl Filson
                                                                     Patent Ductus Arterious
PDA is one of the most commonly diagnosed congenital heart defect in dogs. It is often found in young dogs and is commonly diagnosed in animals less than one year old. Small, young animals can often tolerate this congenital defect for long periods of time and depending on the severity, the age, and size of the dog, heart failure may develop suddenly or not at all.
Before the puppy is born, a passageway called the ductus ateriosus 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. The presence of 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 the heart though 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.
The degree to which the dog is affected depends on the magnitude of the defect. This can range anywhere from a small blind pocket off the aorta which does not cause any problems, to varying degrees of abnormal blood flow through the ductus between the aorta and the pulmonary artery. The most common is a shunt from the left to the right side of the heart, with blood from the higher pressure aorta continuously shunted to the main pulmonary artery. This means an increased volume of blood to the lungs which results in fluid build-up and volume overload to the left heart. Symptoms you may see are coughing, reduced tolerance of exercise, loss of weight, and eventually, heart failure.
Surgical correction of PDA is possible. When the surgery is performed by a veterinary cardiac surgeon, the prognosis is usually excellent. Approximately 64% of dogs with left-to-right shunting PDA will die from complications within a year of diagnosis without surgical correction. Some dogs with modest shunts will survive to maturity, and a few may live 10 years or more.
Fortunately, PDA is usually diagnosed during routine puppy examinations. The vet will hear a distinctive "continuous"  heart murmur that is often described as a "machinery" murmur or "washing machine" murmur that 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.
Less commonly, there is a right-to-left shunt. This may be the case from birth or, it may develop because the PDA is so large that the pressure in the lungs, and the resultant resistance to this pressure, markedly increase. In effect, the circulation is the same as when the dog was a fetus. That is, some of the blood leaving the right side of the heart bypasses the lungs entirely. This results in circulation of poorly oxygenated blood. Symptoms are shortness of breath and weakness or collapse in the hind limbs. The problems associated with the less common right-to-left shunt are managed medically.
This disease is almost always inherited in affected dogs, and one of the breeds prone to having PDA does include the Maltese.
If a puppy is found to have PDA, surgery should be done sooner than later.  Now days, specialty clinics can do this surgery with catheterization.  Once done, the puppy can live a full and normal life.

Affected dogs should NOT be bred. Because PDA is genetically determined in almost every case, parents that produce a PDA puppy, should be withdrawn from their breeding program.

PDA is a prime example of why breeders should always have their puppies health checked by their veterinarian before placing them in pet homes OR keeping them for breeding.



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