Patent Ductus Arteriosus in Puppies and Kittens Explained

Hearing the word "murmur" at a first puppy or kitten checkup can be unsettling. One possible reason for a murmur in a young pet is patent ductus arteriosus, often shortened to PDA. It is one of the better-known congenital heart defects in dogs and is also seen, less often, in cats. The good news is that many pets with the most common form of PDA can go on to live full, active lives when the problem is found early and corrected by a veterinary team. This guide explains what PDA is, how it changes blood flow, which signs warrant a veterinary exam, and what diagnosis, correction, and recovery usually involve.

Important: This article shares general educational information for pet owners and is not a substitute for an in-person veterinary examination, diagnosis, or treatment. For any medical concern or emergency, contact your veterinarian promptly.

What Is the Ductus Arteriosus?

Before birth, a puppy or kitten gets oxygen from its mother through the placenta, not from its lungs. To route blood around the developing lungs, the fetus has a short blood vessel called the ductus arteriosus. It connects the pulmonary artery, which normally carries blood to the lungs, directly to the aorta, the main artery that carries blood to the rest of the body.

At birth, the lungs expand and blood begins flowing through them. Changes in oxygen levels signal the muscle in the wall of the ductus to tighten, and normally the vessel closes within the first days of life.

When closure does not happen, the vessel stays open, or "patent." In many affected dogs, the wall of the ductus is thought to lack enough of the muscle tissue needed to squeeze shut. PDA is therefore a congenital defect: the pet is born with it.

How PDA Affects the Heart and Lungs

After birth, pressure in the aorta is much higher than pressure in the pulmonary artery. If the ductus stays open, blood flows from the high-pressure aorta back into the pulmonary artery. Veterinarians call this a left-to-right shunt, and it is the most common form of PDA.

Extra work for the left side of the heart

Blood that slips through the ductus circulates through the lungs again and returns to the left side of the heart, which must pump it out once more. Over time, this extra volume makes the left heart chambers enlarge. If uncorrected, the strain can lead to congestive heart failure, with fluid building up in the lungs, and abnormal rhythms can develop.

Why the timing matters

Because these changes build gradually, a young pet with PDA may look normal at first, which is why routine puppy and kitten exams matter. For more background, see our guide to heart murmurs in dogs and cats.

Which Puppies and Kittens Are at Risk?

PDA can occur in any dog or cat, including mixed breeds. In dogs, it is recognized more often in certain breeds, and female dogs appear to be affected more often than males. Breeds frequently mentioned in veterinary references include:

• Toy and miniature Poodles
• Pomeranians
• Maltese
• Yorkshire Terriers
• Bichon Frise
• German Shepherds
• Collies

PDA is believed to have an inherited component in dogs, so responsible breeders generally avoid breeding affected dogs and their close relatives.

In cats, PDA is less common and not strongly tied to particular breeds, but a murmur in a kitten still deserves careful follow-up.

Signs That Warrant a Veterinary Exam

Many young pets with PDA show no obvious signs at home early on, and the defect is often first suspected when the veterinarian listens to the chest at a routine checkup.

What your veterinarian may notice

• A continuous murmur: PDA classically causes a murmur heard throughout the entire heartbeat, sometimes described as a "machinery" murmur. It is usually loudest high on the left side of the chest, near the armpit.
• Strong, bounding pulses: the pulse in the inner thigh may feel unusually forceful.
• A palpable vibration: with a loud murmur, the veterinarian may feel a buzzing sensation over the chest wall.

What you might see at home

• Tiring more quickly than littermates during play
• Slower growth or being smaller than littermates
• Fast or effortful breathing, especially at rest or during sleep
• Coughing
• Reluctance to exercise or frequent lying down
• Fainting or collapse

None of these signs alone means a pet has PDA; they are reasons to schedule a veterinary exam, and fainting, collapse, or labored breathing need your veterinarian or an emergency clinic right away.

How Veterinarians Diagnose PDA

Because the PDA murmur is distinctive, a veterinarian may strongly suspect it from the exam alone. Confirming the diagnosis usually involves additional tests.

• Echocardiography: an ultrasound of the heart is the key test. It shows the open ductus, measures its size and shape, reveals the direction of blood flow, and shows how much the heart chambers have enlarged.
• Chest X-rays: these help assess heart size, the major blood vessels, and whether there is fluid in the lungs.
• Electrocardiogram (ECG): this records the heart's electrical activity and can show rhythm changes or patterns that suggest chamber enlargement.
• Bloodwork: routine blood tests help evaluate overall health before anesthesia and, in some cases, red blood cell levels.

Your veterinarian may refer you to a board-certified veterinary cardiologist, who has specialized training and equipment for congenital heart defects.

Correction Options: Surgery and Catheter-Based Closure

For the common left-to-right form, veterinarians generally recommend closing the ductus while the pet is young, before significant heart changes develop. The best approach depends on the pet's size and the shape of the ductus.

Surgical ligation

A veterinary surgeon opens the chest on the left side and ties off the ductus with suture. This long-established approach suits even very small patients, and recovery includes pain management and restricted activity while the incision mends.

Minimally invasive catheter-based closure

Many cardiology centers can instead thread a thin catheter through a blood vessel, often in the hind leg, to the heart and place an occlusion device or coil that closes the ductus. Recovery is often quicker without a chest incision, though very small patients may not be suitable.

Anesthesia and medical support

Both approaches require general anesthesia. A pet with signs of heart failure may first receive heart medications, such as diuretics, as prescribed by your veterinarian. Our article on anesthesia safety for pets explains how teams monitor patients.

Reverse PDA: A Different Situation

In a smaller number of pets, pressure in the lungs' blood vessels rises above pressure in the aorta, and blood flows the opposite way, from right to left. This is called a reverse PDA.

Oxygen-poor blood then travels toward the back half of the body, so the gums may look pink while rear mucous membranes look bluish. Affected pets may have hind leg weakness during exercise, and a loud murmur is usually absent.

Closing a reverse PDA is generally not recommended, because the ductus acts as a pressure release for the strained right heart. Veterinarians focus on long-term management, which may include medications as prescribed by your veterinarian, periodic removal of blood if too many red blood cells are made, and limited exercise.

Caring for Your Pet Before and After the Procedure

While waiting for closure

• Keep play calm and avoid strenuous exercise unless your veterinarian says otherwise
• Watch breathing at rest and note any changes
• Give any prescribed medications exactly as directed
• Keep up good nutrition and routine puppy or kitten care your veterinarian recommends

After going home

Follow discharge instructions carefully. Short leash walks for bathroom breaks, a crate or small room for rest, and quiet enrichment such as food puzzles help an energetic youngster stay calm. Check any incision daily for redness, swelling, or discharge, and use a cone if advised.

Give any pain medication on schedule. Recheck visits, often with a follow-up echocardiogram, confirm the ductus is closed. Our guide to post-surgery recovery care at home offers more tips.

Many pets whose left-to-right PDA is closed before major heart damage go on to enjoy normal activity. Your veterinarian can discuss the outlook for your individual pet.

When to Call Your Veterinarian

Contact your veterinarian promptly to schedule an exam if your puppy or kitten:

• Was told it has a heart murmur and has not yet had follow-up testing
• Tires noticeably faster than other young pets during play
• Is not growing or gaining weight as expected
• Has a new or occasional cough
• Seems to breathe faster than usual at rest

Contact your veterinarian or an emergency clinic right away if

• Your pet is struggling to breathe, breathing with an open mouth, or breathing with a lot of belly effort
• The gums or tongue look blue, gray, or very pale
• Your pet faints, collapses, or cannot stand
• Your pet suddenly becomes very weak, or is restless and unable to settle at night
• After a procedure, the incision is bleeding, gaping, or very swollen, or your pet seems to be in severe pain

These are emergencies; call ahead so the clinic can be ready.

Myths vs. Facts

Myth: A puppy or kitten murmur will always go away on its own.

Fact: Some soft "innocent" murmurs fade with growth, but the continuous murmur typical of PDA does not. Any murmur deserves follow-up.

Myth: If my pet seems healthy, there is no rush.

Fact: PDA often causes no obvious signs while the heart is quietly enlarging.

Myth: Every PDA should be closed.

Fact: Closure is generally recommended for the common left-to-right form, but closing a reverse PDA is usually not advised. Testing tells the team which type is present.

Myth: Only purebred dogs get PDA.

Fact: Certain breeds are overrepresented, but mixed-breed dogs and cats can also be born with PDA.

Frequently Asked Questions

Is PDA painful for my pet?

The defect itself is not thought to be painful, though complications and surgery can cause discomfort that your veterinarian manages carefully.

How young can a pet have the procedure?

Closure is often performed in young puppies and kittens once they are large enough and stable enough for anesthesia. Your cardiologist will advise on timing for your individual pet.

Can my pet live a normal life after PDA closure?

Many pets do, especially when the ductus is closed before major heart changes develop. Follow-up visits help confirm how well the heart has recovered.

Should I breed a dog that had PDA?

Because PDA is believed to be inherited in dogs, veterinarians generally advise against breeding affected dogs. Spaying or neutering can be discussed with your veterinarian.

Will my pet need lifelong medication?

After successful closure of a left-to-right PDA, many pets do not need ongoing heart medication. Pets with reverse PDA or lasting heart changes may need long-term management as prescribed by your veterinarian.

Key Takeaways

PDA occurs when a vessel essential before birth fails to close afterward. In the common left-to-right form, the left heart works harder and can enlarge or fail if uncorrected. A continuous murmur at a routine exam is often the first clue, and echocardiography confirms the type. Surgical or catheter-based closure is generally recommended for left-to-right PDA, while reverse PDA is managed medically. Seek emergency care right away for breathing trouble, blue or pale gums, or collapse. With early detection, many pets do very well.