PDA, or patent ductus arteriosus, is the most common congenital heart defect in dogs. It occurs when a small blood vessel that normally closes within the first few days of life stays open after birth, forcing the heart to work much harder than it should. Without treatment, PDA can lead to heart failure, but the good news is that closure procedures are highly successful and often curative when performed early.
How the Ductus Arteriosus Works
Before a puppy is born, its lungs aren’t being used. A developing fetus gets oxygen through the placenta, so blood doesn’t need to pass through the lungs at all. To bypass them, fetuses have a small vessel called the ductus arteriosus that connects the pulmonary artery (which goes to the lungs) directly to the aorta (which sends blood to the rest of the body). This shortcut makes perfect sense in the womb.
The moment a puppy takes its first breath, everything changes. The lungs inflate, blood begins flowing through them to pick up oxygen, and the pressure in the lung circulation drops dramatically. Oxygen and hormones signal the ductus arteriosus to close, and it typically seals within the first three days of life, becoming a small piece of scar tissue. In some puppies, that closure never happens. The vessel stays open, or “patent,” and the result is a PDA.
What Goes Wrong When It Stays Open
Once a puppy is breathing on its own, blood pressure in the aorta is much higher than in the pulmonary artery. With the ductus still open, blood is continuously pushed backward from the aorta into the pulmonary artery and re-routed to the lungs. This is called a left-to-right shunt, and it means the lungs receive far more blood than they should while the heart has to pump that extra volume over and over again.
Over time, this constant overload stretches and enlarges the left side of the heart. The left atrium swells to accommodate the excess returning blood, and the left ventricle thickens and dilates as it struggles to keep up. If the PDA isn’t corrected, this progressive remodeling leads to congestive heart failure. In a large study of 520 dogs with PDA, not having a closure procedure increased the risk of death by nearly 17 times compared to dogs that were treated.
In rare cases, the pressure dynamics can reverse. When lung pressure rises high enough from chronic overload, blood begins flowing from right to left through the ductus, sending oxygen-poor blood into the body. This reversed PDA is a more serious and complex situation with fewer treatment options.
Breeds and Risk Factors
PDA tends to run in certain breeds. Standard Poodles are particularly well represented, along with their crossbreeds like Goldendoodles, Labradoodles, and Bernedoodles. Other commonly affected breeds include Maltese, Pomeranians, Shetland Sheepdogs, Chihuahuas, and German Shepherds. The condition has a genetic component, so dogs diagnosed with PDA generally should not be bred.
Female dogs are more likely to be affected than males. In most breeds, roughly 73 to 78% of PDA cases occur in females, though the ratio is closer to even in some breeds like German Shepherds.
Signs Your Vet Might Notice First
Many puppies with PDA seem perfectly healthy at first, and the condition is often discovered during a routine veterinary exam. The hallmark sign is a distinctive heart murmur that sounds like a washing machine. Unlike most heart murmurs that occur only during certain phases of the heartbeat, this one is continuous because blood flows through the open ductus nonstop. Vets can hear it best by placing a stethoscope high on the left side of the chest, up near the armpit, rather than in the usual spot.
As the condition progresses, you might notice your puppy tiring easily during play, breathing faster than normal, coughing, or growing more slowly than littermates. Some dogs develop a noticeably strong or “bounding” pulse that you can feel in the femoral artery on the inner thigh. One important caveat: the reversed form of PDA (right-to-left shunting) produces no murmur at all, making it much harder to detect on a standard exam. Dogs with reversed PDA may show weakness in the hind legs or bluish discoloration of the gums and tongue.
How PDA Is Diagnosed
A veterinarian who hears the characteristic continuous murmur will strongly suspect PDA, but an echocardiogram (heart ultrasound) confirms the diagnosis. The ultrasound shows the open vessel directly and uses Doppler flow imaging to visualize blood moving through it. It also measures how much the heart has already enlarged, which helps determine how urgently closure is needed. Chest X-rays often show an enlarged heart silhouette and signs of increased blood flow to the lungs.
Treatment: Closing the Ductus
Correcting a PDA means closing the open vessel, and there are two main approaches. Both are highly effective.
Surgical ligation is the traditional method. A surgeon opens the left side of the chest, identifies the ductus, and ties it off with suture material. It’s a well-established procedure that has been performed for decades.
Catheter-based closure is the minimally invasive alternative. A catheter is threaded through a blood vessel, typically in the leg, and a device is deployed inside the ductus to block it. The most successful device is the Amplatz Canine Ductal Occluder, or ACDO, which has reported success rates of 98 to 100%. Coil embolization is another catheter option, with slightly lower success rates around 86%.
In a study of over 450 closure procedures, the mortality rate was low for both approaches: 1.8% for catheter-based procedures and 2.8% for surgical ligation. The difference between the two was not statistically significant, meaning both are considered safe. The choice between surgery and a catheter procedure often depends on the size of the dog, the shape of the ductus, available equipment, and the expertise of the veterinary team.
Timing matters. Early intervention, ideally before six months of age, is linked to better outcomes and less permanent heart damage. The longer a PDA goes uncorrected, the more the heart remodels, and some of that damage may not fully reverse.
Recovery After Closure
Most dogs recover quickly. The incision site needs to be kept clean and dry, and an Elizabethan collar (cone) prevents licking or chewing at the wound. Activity should be restricted for about 10 to 14 days while the incision heals, meaning no rough play, running, or jumping during that window.
A follow-up echocardiogram is typically scheduled one to three months after the procedure to check whether the heart is returning to a normal size and the closure is holding. In most dogs, the heart does reverse its enlargement over time. One- and two-year survival rates after surgical ligation are approximately 92% and 87%, and PDA closure overall provides significant long-term survival benefits.
Dogs that had their PDA closed before developing heart failure often go on to live completely normal lives with no ongoing cardiac medications. Dogs that already had significant heart changes at the time of closure may need monitoring or medication for residual issues like mitral valve leakage, which was identified as a factor that can affect long-term outcomes even after successful closure.