Overview

The ductus arteriosus carries blood around the fetal lungs into the aorta. It normally closes within days after birth, separating pulmonary and systemic circulation. PDA occurs when it remains open.

Blood continuously flows from the higher-pressure aorta into the lower-pressure pulmonary artery, increasing both pulmonary blood flow and blood returning to the left atrium and ventricle. These chambers enlarge under the added load. Advanced disease can lead to left-sided heart failure and pulmonary edema.

Rarely, flow reverses from a left-to-right to a right-to-left shunt. A murmur alone cannot determine the next step; imaging must establish shunt direction and size.

Predisposed breeds

PDA can occur in any breed but is reported more frequently in the following breeds and is generally more common in females.

Maltese, Toy and Miniature Poodles, Pomeranians, Yorkshire Terriers and Shih Tzus
Bichon Frises, Chihuahuas and Miniature Schnauzers
Cocker Spaniels, Shetland Sheepdogs and Collies
Any breed with a murmur detected in puppyhood

Even outside these breeds, a murmur during a puppy examination warrants assessment for congenital disease, including PDA.

What signs should I watch for?

Small PDAs often cause no obvious change in energy and are found only on auscultation. A large shunt or rapid progression may cause:

A continuous, machinery-like murmur over the left chest, often first found at a veterinary examination
Slower growth or smaller size than other puppies of the same age
Prolonged panting or slow recovery after mild activity
Repeated increases above the usual sleeping respiratory rate
Brief loss of consciousness or unsteadiness when excited (syncope)
Paler or bluish mucous membranes, with cyanosis sometimes more apparent in the hindquarters

Often detected as a murmur before symptoms appear

PDA is often found incidentally during a first vaccination or pre-neutering examination in an apparently healthy puppy. After a primary clinic detects a murmur, detailed imaging to determine shunt direction and size is the next step.

Diagnostic steps

Diagnosis gathers information in stages about shunt direction, size and cardiac load rather than relying on a single test.

Auscultation

Identify the characteristic continuous murmur over the upper left chest, the most common first finding in puppy examinations.
Chest X-rays

Assess left atrial and ventricular enlargement, increased pulmonary vascular markings and, in advanced disease, pulmonary edema.
Echocardiography

Identify duct location and size, using Doppler to assess left-to-right or right-to-left flow and the pressure gradient. This is central to deciding whether to refer for intervention.
ECG

Assess left ventricular enlargement patterns and concurrent arrhythmias; also useful before anesthesia.
Blood tests + NT-proBNP

Assess kidney and liver function, electrolytes and hematocrit. For suspected right-to-left shunting, check for erythrocytosis. NT-proBNP can support heart failure risk assessment.

Stages of progression

PDA progression depends on shunt size and direction and the degree of left-heart load. The broad stages below guide management.

Stage	Condition	Management approach
Asymptomatic	Murmur present, but activity resembles that of peers; little or no left-heart enlargement on imaging	Assess shunt direction and size, then consider referral for closure when indicated
Clinical progression	Slower growth or recovery after exercise, with clear left atrial and ventricular enlargement	Begin medication to reduce left-heart load and assess intervention eligibility promptly
Congestive heart failure	Current or previous left-sided heart failure signs, including pulmonary edema and breathing difficulty	Combination medication for stabilization, followed by reassessment for intervention

These stages illustrate a general course for owners. The veterinarian applies them according to echocardiography, age and concurrent conditions.

Treatment and care by stage

PDA care has two main aims: close the shunt as early and safely as appropriate, and reduce current left-heart load through medication and daily care. Our approach follows these steps.

Shunt closure — Referral

When closure is indicated for a left-to-right shunt, it has a major effect on long-term prognosis. We assess direction and size with ultrasound and refer suitable patients to a cooperating center. We provide imaging follow-up, medication management and pre-anesthetic assessment around the procedure.

Medication combinations by stage

For progressive left-heart enlargement or pulmonary edema, combinations may include diuretics, inotropes, vasodilators and ACE inhibitors. Doses are adjusted while monitoring kidney function, electrolytes and blood pressure.

Home monitoring — Resting respiratory rate (SRR)

Count breaths for one minute while your pet sleeps and compare with the usual rate. Contact the veterinarian if faster breathing recurs and agree on individual contact thresholds. For labored or open-mouth breathing, go straight to the nearest 24-hour emergency veterinary hospital regardless of the count.

Daily care and regular follow-up

Avoid strenuous exercise as appropriate to the stage, while ordinary walks are generally maintained. Adjust walks in hot or humid weather. Imaging follow-up commonly starts at intervals of three to six months and changes with disease stage.

Frequently asked questions

Is detailed testing necessary if there is only a murmur?

Assessment is recommended. Direction and size affect management even in an apparently healthy dog. Ultrasound assesses the shunt and heart size, while symptoms and pulmonary hypertension inform intervention and follow-up decisions.

Do you perform the procedure at your clinic?

We provide outpatient care and daytime hospitalization. Procedures are performed at cooperating centers. We provide imaging, ECG, blood testing and pre-anesthetic assessment, followed by medication management and imaging after the procedure.

Can my puppy be neutered first?

With suspected or confirmed PDA, shunt status and left-heart load should generally be assessed before other surgery requiring anesthesia. Findings may call for postponement or closing the shunt before neutering.

Can PDA be managed with medication alone?

Medication and daily care can limit progression when the shunt is small, closure is not indicated or intervention is not feasible. However, closure generally offers a better long-term outlook for suitable left-to-right shunts, so an eligibility assessment is worthwhile when possible.

Will medication be lifelong after closure?

Medication needs often decrease when closure is successful and left-heart enlargement resolves. If enlargement was already advanced or arrhythmias are present, medication and imaging follow-up commonly continue for a period.

What if symptoms suddenly worsen?

For difficult breathing, blue gums or loss of consciousness, go straight to the nearest 24-hour emergency veterinary hospital without waiting for our outpatient appointment. Pulmonary edema needs prompt stabilization.

References

These external resources provide more detail on PDA diagnosis and treatment and puppy murmurs. They do not define our services or an individual prescription.

Patent ductus arteriosus (PDA)