© Kirrawee Veterinary Hospital FELINE DISEASES
Patent Ductus Arteriosis
The ductus arteriosus is a blood vessel present in unborn animals
which runs from the pulmonary artery to the aorta allowing blood
to bypass the lungs. At birth muscles in the ductus are stimulated
to contract, decreasing the size of the bypass, and directing
blood to the newly inflated lungs. Over the first week of life
the ductus normally closes completely. In some puppies the ductus arteriosis fails to close (patent ductus
arteriosis- PDA). This is an inherited condition (polygenic transmission)
whereby the muscles which should contract to close the ductus
are abnormal. Some of the blood returning from the body to the
heart fails to pass through the lungs before returning to the
circulation. Not only is this oxygen level in the blood reduced
but the bypass causes increased pressure in the left side of the
heart leading to dilation and eventually left sided heart failure. PDA puppies may only show poor growth and poor tolerance to exercise
in the early stages. As left sided heart failure develops coughing
and panting may become more pronounced. The most prominent clinical finding is a heart murmur (shhh sound)
and possibly a vibration (thrill) which can be felt on the lower
left chest wall. These due to the turbulence created by the blood
rushing through the PDA. Xray and ultasound are used to confirm
the diagnosis. Recommended treatment is surgical closure of the PDA. This is
generally carried out between 2 and 4 months of age. Although
there is a small risk of death associated with the surgery treated
dogs have a good long term outlook compared with untreated dogs.
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