If You Hear a Heart Murmur in Your Puppy — Causes and Treatment Timing for Patent Ductus Arteriosus (PDA)

HeartDiseasesMeongsiljang Veterinary Advisory Board

Patent ductus arteriosus (PDA) in puppies is a congenital heart condition where a blood vessel that should close at birth remains open, placing extra strain on the heart. Early detection and surgery can lead to a complete cure, so it's important to be familiar with the symptoms and treatment options.

What Is Patent Ductus Arteriosus? A Congenital Heart Disease in Puppies

Patent ductus arteriosus (PDA) is a congenital heart defect in which the fetal blood vessel that bypasses the lungs, the ductus arteriosus, fails to close after birth, placing excessive strain on the heart. Early detection and prompt treatment are crucial. Closing the patent ductus arteriosus as early as possible allows the enlarged ventricles to shrink, enabling the heart to recover to near-normal function. If left untreated, the condition can progress to left-sided congestive heart failure, significantly shortening the pet’s lifespan. If you notice symptoms such as coughing, rapid breathing, or reluctance to exercise, please have your pet evaluated immediately at a veterinary clinic equipped for cardiac care.

Why Does It Occur? — Causes and Pathogenesis of Patent Ductus Arteriosus

Patent ductus arteriosus (PDA) is known to have a strong genetic predisposition. In the fetus, the ductus arteriosus remains open due to low oxygen pressure and the effects of prostaglandins, allowing blood to bypass the lungs. After birth, as oxygen levels rise, this vessel should naturally close. If this process is disrupted, the ductus remains open. This abnormal passage allows blood to circulate improperly, placing excessive strain on both the heart and lungs. PDA is approximately three times more common in female dogs than in males. While it frequently occurs in breeds such as Poodles, Maltese, Pomeranians, Collies, and Chihuahuas, it has also been reported at high rates in large breeds like Doberman Pinschers, German Shepherds, and Newfoundlands.

Suspect PDA If You See These Symptoms — Key Symptom Checklist

Coughing: When excessive blood flow to the lungs causes congestion, chronic coughing may recur.

Rapid breathing/panting (dyspnea): Inadequate oxygen supply leads to rapid breathing or abdominal heaving.

Exercise intolerance/fatigue: Reduced cardiac efficiency causes quick exhaustion with minimal activity, and occasionally fainting.

Growth and development impact: In young puppies, growth may lag behind peers depending on their condition.

Continuous heart murmur: Auscultation reveals a continuous, machine-like sound without interruption, which is a characteristic finding of left-to-right shunting PDA.

Cyanosis: In right-to-left (reverse) shunting PDA, differential cyanosis (bluish discoloration of the hindquarters, including the hind legs and tail mucous membranes) and hindlimb weakness may occur, serving as an emergency warning sign.

Dogs showing symptoms of exercise intolerance and panting

Go to the Emergency Room Immediately! Never Wait If You See These Symptoms

If your pet suddenly collapses or loses consciousness, experiences severe respiratory distress causing the entire body to tremble, or shows differential cyanosis (bluish discoloration of the rear body parts, including the hind legs and tail mucous membranes) due to a reversed patent ductus arteriosus (PDA), take them to a 24-hour emergency veterinary clinic immediately. Do not miss the critical window for treatment.

How Is It Diagnosed? — Overview of Diagnostic Tests

At the veterinary clinic, suspicion arises when a characteristic "continuous heart murmur" is detected with a stethoscope. For a definitive diagnosis, an echocardiogram (cardiac ultrasound) is the most critical test, as it allows precise evaluation of the patent ductus arteriosus's location, size, and blood flow direction. A chest X-ray is used to assess for cardiac enlargement and pulmonary congestion, while an electrocardiogram checks for arrhythmias. Blood tests are also performed to evaluate overall cardiac function.

How Is It Treated? — Catheter-Based Procedure vs. Surgical Repair

The key to treatment is closing the patent ductus arteriosus.

Catheter-based procedure (minimally invasive): This approach involves closing the ductus arteriosus using specialized devices, such as coils, inserted through a blood vessel in the thigh. Because it requires no incisions, recovery is swift, making it the most commonly chosen option today.

Surgical ligation: This traditional surgery involves opening the chest to directly tie off the ductus arteriosus. It is typically selected when a catheter-based procedure is not feasible.

Both methods have high success rates, and the earlier the treatment is administered, the greater the likelihood that the heart will return to its normal size.

Procedure footage of catheter-based intervention for patent ductus arteriosus in dogs

How to Care for Your Pet at Home After Surgery

For the first 2 to 4 weeks after surgery, avoid strenuous exercise and ensure your pet gets plenty of rest. Regular follow-up cardiac ultrasounds are necessary to monitor whether the heart size is returning to normal. If heart failure has already developed, it is essential to consistently administer the heart medications prescribed by your veterinarian. A low-sodium diet is recommended, and you should avoid causing extreme excitement or engaging in high-intensity exercise. Contact your clinic immediately if you notice any abnormalities, such as changes in appetite, coughing, or breathing.

A puppy recovering at home after surgery

If Your Dog Is One of These Breeds, Request Cardiac Auscultation at the First Postnatal Checkup

Poodles, Maltese, Pomeranians, Collies, Chihuahuas, German Shepherds, Cocker Spaniels, and Welsh Corgis are reported to have a relatively higher risk of patent ductus arteriosus. It is especially more common in females. Be sure to request a cardiac auscultation during your puppy’s first vaccination visit at two months of age. If a continuous heart murmur is detected during auscultation, it is advisable to promptly undergo an echocardiogram.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

What happens if a patent ductus arteriosus is left untreated surgically?

If left untreated, the heart gradually enlarges and progresses to left-sided congestive heart failure. Initially, there may be no symptoms, but it can lead to pulmonary congestion and arrhythmias. Without treatment, life expectancy can be significantly shortened.

At what age is it best to have surgery?

It’s best to undergo treatment as soon as a diagnosis is made. The earlier the arterial blockage is addressed, the more likely the enlarged heart will shrink and return to near-normal function. Older dogs often have accumulated heart damage, so a thorough pre-surgical evaluation is essential.

Which is better, catheter placement or thoracotomy?

The most suitable approach depends on the size and location of the ductus arteriosus, as well as any concurrent conditions. Catheter-based procedures (minimally invasive) offer the advantage of faster recovery since they don't require surgical incisions, but in some cases, surgical ligation via thoracotomy may be more appropriate. Please discuss thoroughly with your veterinarian to determine the best option for your pet.

Should my pet continue taking heart medication after surgery?

If surgery is performed early and the heart size recovers well, medication may not be necessary. However, if heart failure has already progressed, consistent medication prescribed by a veterinarian will be required even after surgery.

Is patent ductus arteriosus hereditary? Can it occur in sibling dogs as well?

This condition is known to have a genetic predisposition. Siblings born to the same parents may also be at risk. If your dog has littermates, it’s a good idea to have them all undergo a cardiac auscultation during their first veterinary checkup.

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References

[1] Chetboul V, et al. Textbook of Cardiovascular Medicine in Dogs and Cats. Éditions du Point Vétérinaire, 2016.

[2] Schaer M (ed.). Clinical Medicine of the Dog and Cat, 4th Ed. CRC Press, 2022.

[3] Bussadori C, Carminati M, Domenech O. Transcatheter closure of a perimembranous ventricular septal defect in a dog. J Vet Intern Med, 2007, 21:1396–1400.

[4] Bussadori C, Domenech O, Longo A, et al. Percutaneous catheter-based treatment of pulmonic stenosis and patent ductus arteriosus in a dog. J Vet Cardiol, 2002, 4:29–34.