Patent Ductus Arteriosus

At birth, mammals must adapt from living in a fluid environment (the amniotic fluid) and acquiring oxygen through the mother's blood, to breathing air and acquiring oxygen through their own lungs. The ductus arteriosus is very important in the adaptation process. This is a small communicating blood vessel between the pulmonary artery (which carries blood to the lungs), and the aorta (which carries blood to the rest of the body).  Before birth, most of the blood from the fetal heart bypasses the fetal lungs via the ductus arteriosus. The lungs gradually become functional fairly late in fetal development. At birth, the blood supply from the mother is of course cut off, the dog (or other mammal)  begins breathing on its own, and blood flow through the ductus arteriosus decreases dramatically. Within a few days, the ductus closes off completely.
Where the ductus does not close, the dog is left with a patent ductus arteriosus (PDA) condition.   The extent to which this affects the dog depends on the degree of patency, or opening, of the ductus.

Patent Ductus Arteriosus or PDA is the most commonly diagnosed congenital heart defect in dogs. It occurs in many breeds and is seen more often in females. The breeds at most risk for patent ductus arteriosus are the Maltese, Pomeranian, Shetland sheepdog, and Kerry blue terrier.   Other breeds with an increased risk of patent ductus arteriosus are the Keeshond, miniature and toy poodle, Bichon frise, Yorkshire terrier, English springer spaniel, collie, cocker spaniel, German shepherd, Irish setter and Chihuahua.  

The degree to which the dog is affected depends on the magnitude of the defect. Patent ductus arteriosus can range anywhere from a small blind pocket off the aorta which doesn't cause any problems, to varying degrees of abnormal blood flow through the ductus between the aorta and the pulmonary artery.  Without surgery, premature death is likely.

Usually patent ductus arteriosus is first suspected when the veterinarian hears the characteristic continuous "machinery" heart murmur when your dog is examined at the time of vaccination. There are radiographic and electrocardiographic signs to confirm the patent ductus arteriosus diagnosis. Your puppy will not likely show any clinical signs relating to the patent ductus arteriosus. 

To treat patent ductus arteriosus, surgery is recommended in all dogs less than 2 years of age in which a left-to-right shunting PDA has been diagnosed. Surgical treatment of patent ductus arteriosus consists of tying off the patent ductus and is quite successful. Surgery should be performed as soon as possible - as early as 8 to 16 weeks of age - before changes have occurred as the heart tries to compensate for the defect.