Issue Description 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.
the ductus does not close, the dog is left with a patent ductus
The extent to which this affects the dog depends on the degree of
patency, or opening, of the ductus. Other Names PDA
Symptoms The degree to which your dog is affected
depends on the magnitude of the defect. This 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. Most commonly there 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 (pulmonary edema) and volume overload to the left heart. You
may see coughing, reduced tolerance of exercise, loss of weight, and
eventually, congestive heart failure. Without surgery, premature death
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 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. Your dog may have shortness
of breath and weakness or collapse in the hind limbs.
Diagnosis Usually a PDA 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 diagnosis.
At this point your puppy will not likely show any clinical signs
relating to the PDA.
Treatment 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 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. The prognosis for a normal
life with early surgery is usually very good. Where there are signs of
heart disease, there are increased risks associated with surgery and
your veterinarian will recommend medical stabilization before surgery.
The problems associated with the less common right-to-left shunt are
managed medically rather than surgically. Treatment includes rest,
exercise restriction, and avoidance of stress. Your veterinarian will
monitor and work with you to manage the changes which occur due to the
circulation of poorly oxygenated blood.
Breeds Most Affected PDA is the most commonly diagnosed congenital
heart defect in dogs. It occurs in many breeds and is seen more often
The breeds at most risk for this disorder are
the Maltese, Pomeranian, Shetland Sheepdog, and Kerry Blue Terrier.
Other breeds with an increased risk are the Keeshond, Miniature and
Toy Poodle, Bichon Frise, Yorkshire Terrier, English Springer Spaniel,
Collie, Cocker Spaniel, German Shepherd, Irish Setter and Chihuahua.