Patent Ductus Ateriosis (PDA)

One of the most common canine birth defects.  Normally in the fetus, the Ductus Arteriosis is a blood vessel which bypasses the lungs to circulate oxygen until birth when this vessel will naturally close and regress as the lungs take over the function of oxygenation.  When this vessel fails to close, blood will continue to be diverted, causing the heart to work much harder than normal.  If untreated, this can result in premature death due to heart failure.

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Symptoms: Heart murmur, particularly a continuous heart murmur in puppies or young dogs,, chronic coughing, breathing difficulties, weakness, exercise intolerance, congestive heart failure.  More often seen in females than males. 

Treatment Options: Surgery to close the vessel at the earliest time possible after diagnosis.  Dogs that have had corrective surgery for PDA have been able to lead relatively normal lives.

Known Mode of Inheritance:  Unknown in Cardigans.  Identified as a proven inherited, but complex issue in other breeds.

Age of onset: birth

Breeds affected

  • Cardigan: yes
  • Pembroke: yes
  • Other Breeds: yes, the GSD, Maltese, Cocker Spaniel, Poodle, Pomeranian, and Shetland Sheepdog have been identified at higher risk.

Incidence in Cardigans: Uncertain. Incidence may be relatively low, but it has been reported in the breed.


  • Cardigans: no
  • Other breeds: yes
  • Active?: yes, but currently only for Shetland Sheepdogs.

Registry: Not specifically for this disorder, but the OFA does have a Cardiac Database which is currently being improved.

DNA Tests Available: no

Research links:

Published papers and Articles:

Discussion Groups:



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