The Ductus Arteriosus
Between the aorta and the pulmonary artery (the two main blood vessels from the heart) is an arterial shunt called the ductus arteriosus. It usually develops along with the fetus, and it serves the purpose of allowing most of the circulating blood to bypass the lungs and supply the body with oxygen from the placenta. This means that while the fetus is still in the mother's uterus, the ductus arteriosus is usually open (patent).
When a puppy is born and takes their first breath, this stimulates the ductus arteriosus to close, ensuring the blood circulates normally through the now-inflated lungs and becomes oxygenated.
Symptoms Of PDAs In Dogs
If a dog has a small PDA defect, there may not be obvious signs of the condition at first. As the PDA increases in size, there is more and more blood shunting through it, leading to more obvious symptoms. These signs can include:
- Difficulty breathing
- Loud heart murmur
- Abnormal pulses
- Intolerance for exercise
- A puppy with a PDA may sleep more than usual, be thinner or smaller in growth than average, or appear stunted in growth.
- Accumulation of fluid in lungs/abdomen (more advanced cases)
It is important to keep in mind that other complex heart conditions besides PDA can cause heart murmur. To distinguish between PDA and other potential issues, it's recommended to have your pet examined and tested with an ECG.
If left untreated, blood will continuously shunt through the PDA, leading to irreversible changes to the heart muscle and potentially causing congestive heart failure. If the PDA is this advanced, additional symptoms could also include heart arrhythmia and noisy breathing when listened to with a stethoscope.
If the shunt is quite large, the pulmonary circulation pressure could increase until it is more than the pressure in the aorta. If this occurs, the shunt might reverse – this means that blood returning from the body takes a shortcut through the aorta before continuing to the lungs for oxygenation. This 'reverse PDA' causes the symptoms of heart murmurs to disappear, but others to become significantly more severe. Advanced cases and/or 'reverse PDA' can cause the following symptoms:
- Abnormal heartbeats
- Cyanosis (blueness) footpads on
- Hind leg collapse during exercise
- Weakness or lethargy
How is PDA diagnosed?
When your vet listens to your puppy's chest during a routine physical check, they may hear a 'continuous' heart murmur (present during the entirety of the heart cycle, also called a 'washing machine murmur' due to its sound). There are two scales of grading heart murmurs in dogs: one is graded between 1–4 and 1–6. Using this scale, your veterinarian can have an idea of the severity of your dog's condition.
Your dog's chest will be X-rayed to see the heart and lungs more clearly, and an electrocardiogram (ECG) will be carried out to observe the heart rhythm. Blood tests may also be taken to ascertain whether other internal organs are being negatively affected by abnormal blood flow or unusual red blood cell values.
Other tests, such as echocardiography (cardiac ultrasound), are needed to diagnose a PDA accurately. The technician can assess a moving image of the heart to observe the structure and functionality of the affected heart walls.
What is the treatment for a PDA dog?
The main focus of treating a PDA in a dog is stopping the blood from flowing through the shunt. Your primary vet will refer you to a veterinary cardiovascular surgeon, who can help you choose the best treatment for your dog's unique case. Whether the condition can be treated via heart surgery to tie off the ductus or a less invasive procedure to block off (occlude) the ductus with a special device, a vet specialist should perform a repair as soon as possible. If surgical treatment is delayed, it becomes more likely that there will be irreversible damage to the dog's heart.
Unfortunately, there is no surgical treatment for a reverse PDA. The symptoms can be managed with medical treatment, but the condition is not curable.
Life Expectations of a Dog with PDA
PDA can affect the normal lifespan of a dog unless it's fixed with surgery or if the issue is very small. It's best to find and treat PDA in dogs before they show any symptoms, especially when they're young (less than 6 months old). This way, surgery can be done to fix the problem and give them a good chance at a normal life.
A dog that has surgery for PDA when they're young usually recovers well and has a regular life span. If the condition isn't fixed early, even surgery later might not fully fix the heart. Still, it's recommended to do the surgery as it helps prevent more damage to the heart.
The sooner PDA is treated in a pet's life, the lower the chances of problems in the future and the better their overall life expectancy.
If the surgery isn't chosen, you can talk to your vet about medicines to keep your dog comfortable. Without surgery, the outlook is about 2-3 years, except in rare cases for life expectancy.
Advanced Care for Dogs
It is important to provide route care for new puppies to diagnose heart conditions early for proper treatment. Whether your dog requires surgical intervention or medical support, our Englewood team is committed to working with you to ensure your pet's health, comfort, and quality of life.
Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.