04 Apr Patent Ductus Arteriosus (PDA) in Dogs
Patent ductus arteriosus (PDA) is one of the most frequently diagnosed congenital heart defects in dogs—and one of the few that can be completely corrected with timely treatment. While this condition starts as a simple failure of a fetal blood vessel to close, its consequences can be life-threatening if left untreated.
Understanding how PDA develops, the signs to watch for, and the treatment options available can make all the difference for a dog’s health and longevity. In this article, we’ll break down what PDA heart defect in dogs is, how it affects the heart and lungs, and why early diagnosis is key to saving lives.
What is PDA?
Patent ductus arteriosus (PDA) is one of the three most common congenital heart defects in dogs. It occurs when the ductus arteriosus, a fetal blood vessel, fails to close after birth, leading to abnormal blood flow between the aorta and pulmonary artery.
The Role of the Ductus Arteriosus Before Birth
During fetal development, the lungs are fluid-filled and nonfunctional, so oxygen is supplied by the mother through the umbilical circulation. The ductus arteriosus is a specialized blood vessel that allows blood to bypass the lungs by shunting it from the pulmonary artery directly into the aorta, ensuring efficient oxygen delivery to the developing body.
At birth, when a puppy takes its first breath, several physiological changes occur:
- The lungs fill with air, reducing pulmonary vascular resistance.
- Blood naturally begins to flow into the lungs instead of bypassing them.
- Oxygen exposure triggers the ductus arteriosus to constrict and close, forming a ligamentous structure over the next 7 to 10 days.
What Happens in PDA?
In some puppies, the ductus arteriosus fails to close, leaving an open (patent) vessel between the aorta and pulmonary artery. This allows blood to flow backward, from the aorta (high pressure) into the pulmonary artery (low pressure). The result is excessive blood volume in the lungs and left heart, leading to:
- Increased lung congestion
- Heart enlargement (due to volume overload
- Risk of congestive heart failure
Why Does the Ductus Arteriosus Stay Open?
The failure of the ductus arteriosus to close in dogs is often due to abnormal smooth muscle development, preventing it from constricting properly.
Clinical Signs of PDA Heart Defect in Dogs
The severity of PDA varies depending on the size of the defect and the amount of blood shunting.
- Small PDA: No or mild symptoms; dogs may live normal lives if the defect is small enough.
- Moderate PDA: Mild exercise intolerance, occasional coughing, or increased breathing effort.
- Large PDA: Severe signs such as labored breathing, coughing, lethargy, heart failure, and even sudden death.
A Characteristic Murmur: The “Washing Machine” Sound
PDA produces a continuous, machine-like murmur heard best on the left side of the chest. This murmur results from constant turbulent blood flow through the open ductus.
However, murmurs are not always detected, especially in:
- Very young puppies, where subtle murmurs may be overlooked.
- Unfamiliar settings, where a nervous or squirming puppy may make auscultation difficult.
- Atypical presentations, where other heart conditions mask or alter the murmur.
Breeds at Higher Risk for PDA
Certain breeds have a genetic predisposition to PDA, including:
- Miniature Poodle
- Chihuahua
- Maltese
- Pomeranian
- Cocker Spaniel
- Bichon Frise
- Collie
- Shetland Sheepdog
- German Shepherd
Diagnosing PDA Heart Defect in Dogs
- Auscultation (Listening to the Heart): Identifies the continuous murmur but requires confirmation through imaging.
- Chest X-rays: Reveal heart enlargement and lung congestion.
- Echocardiography (Cardiac Ultrasound): The gold standard for diagnosis, confirming:
- The presence of PDA
- The direction of shunting (left-to-right vs. right-to-left)
- Any secondary heart changes
Why Early Diagnosis Matters
Early detection is critical because untreated PDA leads to heart failure. Delayed diagnosis can result in irreversible damage, reducing the success of intervention.
Treatment Options for PDA Heart Defect in Dogs
PDA is one of the few congenital heart defects in dogs that can be completely corrected if treated early. The two primary treatment options are:
- Surgical Ligation
- Procedure: The ductus arteriosus is tied off with sutures, preventing abnormal blood flow.
- Performed by: Specialist veterinary surgeons due to the delicate nature of the procedure.
- Success Rate: 95%+ with early intervention.
- Considerations: Requires open-chest surgery, making it more invasive than catheter-based options.
- Transcatheter (Endovascular) Occlusion
- Procedure: A small device (such as an Amplatzer Canine Ductal Occluder (ACDO) or an Amplatzer Vascular Plug) is placed via a catheter threaded through the femoral artery, sealing the PDA from inside.
- Advantages: Minimally invasive, faster recovery time, and lower risk of complications than surgery.
- Success Rate: 95%+ in left-to-right PDA cases.
- Limitations: Not feasible for very small puppies due to size constraints of catheter-based devices.
What Happens if PDA is Left Untreated?
Without treatment, moderate to large PDAs cause progressive heart failure. The left heart becomes overworked, leading to:
- Congestive heart failure (fluid buildup in lungs)
- Pulmonary hypertension (high lung pressure)
- Eisenmenger’s Syndrome (a severe, irreversible condition where shunting reverses from left-to-right to right-to-left, leading to chronic low oxygen levels and cyanosis)
Once PDA progresses to right-to-left shunting, surgical or catheter-based correction is no longer an option, and only palliative care is possible.
Prognosis After PDA Closure
- Early correction leads to a normal lifespan with no long-term complications.
- Dogs treated early have an excellent prognosis, often with no need for lifelong medication.
- If left untreated, survival beyond 1-2 years is unlikely in cases of significant shunting.
Key Takeaways
- PDA is a common congenital heart defect that can be cured with early treatment.
- Left-to-right PDA results in excessive blood flow to the lungs and volume overload of the heart.
- A continuous “washing machine” murmur is the hallmark of PDA.
- Echocardiography is required for definitive diagnosis.
- Surgical ligation and transcatheter occlusion both offer a >95% success rate.
- Without intervention, PDA leads to heart failure and premature death.
Final Thoughts
Patent ductus arteriosus may sound complex, but its management is a clear example of how early veterinary care can change the course of a dog’s life. With advanced diagnostic tools and highly successful surgical and catheter-based treatments, most dogs with PDA can go on to live normal, healthy lives.
Whether you’re a pet owner, breeder, or veterinary professional, being aware of the signs—especially the characteristic “washing machine” heart murmur—and acting quickly can make a critical difference. PDA is a reminder that congenital conditions, while serious, don’t have to be a life sentence when caught early and treated effectively. Contact us today at Animal Cardiology Specialists of Nevada to schedule an appointment.
Images used under creative commons license – commercial use (04/04/2025) Image by FROGGYTUFF from Pixabay