Patent Ductus Arteriosis (PDa)
What is patent ductus arteriosus (PDA)?
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). The extent to which this affects the dog depends on the
degree of patency, or opening, of the ductus.
How is patent ductus arteriosus inherited?
Inheritance is complex.
What breeds are affected by patent ductus arteriosus?
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 this disorder are the Collie 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, cocker
spaniel, German shepherd, Irish setter and Chihuahua.
For many breeds and many disorders, the studies to determine the mode of
inheritance or the frequency in the breed have not been carried out, or are
inconclusive. We have only listed breeds for which there is a strong
consensus among practitioners that the condition is significant in this breed.
What does patent ductus arteriosus mean to your dog & you?
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 is likely.
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.
How is patent ductus arteriosus diagnosed?
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.
FOR THE VETERINARIAN:
MURMUR: continuous "machinery" murmur - (disappears with right-to-left
shunt).
ELECTROGARDIOGRAM: left atrial enlargement, left ventricular dilation and
hypertrophy, (right ventricular hypertrophy with right-to-left shunt).
RADIOGRAPHS: pulmonary over-circulation, left atrial and ventricular
enlargement, possibly dilation of the descending aorta and main pulmonary
artery (right ventricular hypertrophy with right-to-left shunt).
ECHOCARDIOGRAPHY: left sided cardiac enlargement and dilation of aorta
and pulmonary artery (right ventricular hypertrophy with right-to-left shunt).
OTHER: signs of pulmonary edema and left-sided heart failure. In a right-to-left
shunt, unoxygenated blood directly from the pulmonary artery mixes with
blood from the lungs in the descending aorta causing differential weakness
and cyanosis in the hind end. Desaturated arterial blood also goes to the
kidneys, causing hypoxemia, polycythemia, and hyperviscosity. The PCV
often exceeds 65 per cent.
How is patent ductus arteriosus treated?
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.
Breeding advice
Dogs in whom PDA has been diagnosed, with or without surgical correction,
should not be used for breeding. Their parents should not be bred either, and
siblings should only be used after careful screening. If any affected offspring
are born, breeding of the parents should be discontinued.
What is patent ductus arteriosus (PDA)?
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). The extent to which this affects the dog depends on the
degree of patency, or opening, of the ductus.
How is patent ductus arteriosus inherited?
Inheritance is complex.
What breeds are affected by patent ductus arteriosus?
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 this disorder are the Collie 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, cocker
spaniel, German shepherd, Irish setter and Chihuahua.
For many breeds and many disorders, the studies to determine the mode of
inheritance or the frequency in the breed have not been carried out, or are
inconclusive. We have only listed breeds for which there is a strong
consensus among practitioners that the condition is significant in this breed.
What does patent ductus arteriosus mean to your dog & you?
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 is likely.
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.
How is patent ductus arteriosus diagnosed?
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.
FOR THE VETERINARIAN:
MURMUR: continuous "machinery" murmur - (disappears with right-to-left
shunt).
ELECTROGARDIOGRAM: left atrial enlargement, left ventricular dilation and
hypertrophy, (right ventricular hypertrophy with right-to-left shunt).
RADIOGRAPHS: pulmonary over-circulation, left atrial and ventricular
enlargement, possibly dilation of the descending aorta and main pulmonary
artery (right ventricular hypertrophy with right-to-left shunt).
ECHOCARDIOGRAPHY: left sided cardiac enlargement and dilation of aorta
and pulmonary artery (right ventricular hypertrophy with right-to-left shunt).
OTHER: signs of pulmonary edema and left-sided heart failure. In a right-to-left
shunt, unoxygenated blood directly from the pulmonary artery mixes with
blood from the lungs in the descending aorta causing differential weakness
and cyanosis in the hind end. Desaturated arterial blood also goes to the
kidneys, causing hypoxemia, polycythemia, and hyperviscosity. The PCV
often exceeds 65 per cent.
How is patent ductus arteriosus treated?
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.
Breeding advice
Dogs in whom PDA has been diagnosed, with or without surgical correction,
should not be used for breeding. Their parents should not be bred either, and
siblings should only be used after careful screening. If any affected offspring
are born, breeding of the parents should be discontinued.
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