🫀 Patent Ductus Arteriosus (PDA) in Dogs and Cats: A Vet’s 2025 Guide to Diagnosis & Treatment 🐶🐱

By Dr Duncan Houston, BVSc

Patent ductus arteriosus (PDA) is one of the most common congenital heart defects in dogs — and can occur in cats too. While serious, it's one of the few heart conditions that can be cured with surgery or catheter-based closure. In this comprehensive 2025 guide, I’ll explain everything you need to know about PDA — from embryology to diagnosis, and your pet’s treatment options. 🩺🐾

🧬 What Is PDA and How Does It Develop?

In the womb, puppies and kittens don't breathe air, so they don’t need blood to flow to their lungs. Instead, they rely on a blood vessel called the ductus arteriosus that acts like a shortcut, allowing blood to bypass the lungs and go straight from the pulmonary artery to the aorta. 🔄

At birth, when the baby takes its first breath, the lungs expand and the ductus should close within the first few days, becoming a ligament (the ligamentum arteriosum). But if it fails to close, the vessel stays open — or "patent" — and becomes a patent ductus arteriosus. 🛑

🐶 Which Breeds Are Affected?

PDA is more common in female dogs and certain breeds:

• 🐾 Maltese
• 🐾 Pomeranian
• 🐾 Shetland Sheepdog
• 🐾 Springer Spaniel
• 🐾 Cocker Spaniel
• 🐾 Bichon Frise
• 🐾 Chihuahua
• 🐾 Miniature Poodle
• 🐾 Labrador Retriever
• 🐾 Yorkshire Terrier

💔 How Does PDA Affect the Heart?

Left-to-Right Shunting (Most Common)

When the ductus remains open, high-pressure blood from the aorta gets shunted into the low-pressure pulmonary artery — a reversal of what happened in the womb. This extra blood volume returns to the heart unnecessarily, making the left side of the heart work harder. 💦

Over time, the heart enlarges and may eventually fail, resulting in left-sided congestive heart failure (CHF). Fluid can also leak into the lungs (pulmonary edema), causing symptoms like:

• 😮‍💨 Rapid or labored breathing
• 🐕 Exercise intolerance
• 🛌 Failure to thrive
• ⚠️ Collapse with exertion

Right-to-Left Shunting (Rare & Severe)

In rare cases, pulmonary blood pressure gets so high that flow reverses — blood travels from the pulmonary artery into the aorta. This means deoxygenated blood is sent to the body, especially to the hind limbs, leading to symptoms like:

• 💢 Exercise-induced weakness
• 🦵 Hindlimb cramps
• 😵 Seizures (from high red blood cell counts)

🔍 How Is PDA Diagnosed?

Most left-to-right PDAs are discovered during routine exams when your vet hears a distinctive continuous murmur — often compared to a “washing machine.” 🎧

🩺 Diagnostic Tools:

• 📻 Stethoscope: Murmur best heard in the left armpit
• 🖼️ X-rays: Check for heart enlargement or fluid in the lungs
• 🫀 Echocardiogram: Visualizes the PDA and measures chamber sizes
• 💉 Bubble study: For detecting rare right-to-left PDA

💡 Treatment Options for PDA

🎯 Left-to-Right PDA

If the PDA is small, no treatment may be needed. But larger PDAs usually require surgical closure or a minimally invasive device to avoid heart failure. 🛠️

🔧 Surgical Ligation

The chest is opened and the PDA tied off with suture. This is most often used for:

• 🐱 Cats
• 🐶 Very small dogs (<5 lbs)

✅ Success rate: ~95%
⚠️ Complications: < 5%, usually with fragile vessels

🩹 Endovascular Occlusion

This is now the preferred method for most dogs. Through a small catheter, a device like the Amplatzer Canine Ductal Occluder (ACDO) is inserted and placed inside the PDA to plug it. No open surgery is required! 🚫🔪

• 🔄 Immediate closure in most cases
• 🔓 Sometimes coils are used instead
• ⚠️ Not feasible for very small puppies

❌ Right-to-Left PDA Treatment

This type cannot be closed surgically. Instead, the goal is managing complications:

• 🩸 Phlebotomy (blood letting): Decreases red blood cells
• 💊 Hydroxyurea or other meds: Suppress red cell production

Sadly, pets with this form usually have reduced life expectancy (~5–6 years). 😢

⏳ When Should PDA Be Treated?

The sooner the better. Most cardiologists recommend correction by 6–12 months of age. Waiting increases surgical risk because the PDA becomes fragile and more likely to tear. 🧠

📈 Prognosis After PDA Correction

✅ With successful PDA closure (especially early), pets can live completely normal lives!

• 🐶 Dogs treated before heart damage can thrive for many years
• 🧓 Older pets may need lifetime medication if treated late

This is one of the few curable congenital heart defects in pets. 🎉

📱 Get Support with Ask A Vet

If your pet has a heart murmur or has been diagnosed with PDA, download the Ask A Vet App for 24/7 veterinary support, procedure advice, and help monitoring symptoms. 🐾❤️

• 💬 Chat with licensed vets anytime
• 📋 Get care plans tailored to PDA
• 📈 Track respiratory rate and heart meds

Visit AskAVet.com for trusted support and resources. 🐶📲

🧠 Final Thoughts from Dr Duncan Houston

PDA is serious, but highly treatable. With timely diagnosis and proper intervention, your dog or cat can live a long, healthy life — often completely symptom-free. If your pet has a murmur, don’t delay. ❤️🩺

Whether you need help with a diagnosis or are seeking the right treatment path, Ask A Vet is always here to guide you. 🐾🫀