Guide: heart murmur in puppies
Heart Murmur in Puppies: Innocent Murmurs and When to Worry
A heart murmur in puppies is an extra whooshing sound that a vet hears through a stethoscope. Many are soft, harmless “innocent” murmurs that fade by about six months of age. A loud murmur, or one that lasts, needs a heart ultrasound to find the cause.
What a heart murmur is
A normal heartbeat makes two clear sounds. A murmur adds a whooshing noise between them. VCA Animal Hospitals explains that the sound comes from turbulent blood flow inside the heart (VCA).
A murmur is a finding, and it is not a diagnosis. It tells the vet to look closer. Some murmurs mean nothing, while others point to a defect in the heart.
Innocent heart murmur in puppies
Most murmurs in young puppies turn out to be harmless. Cornell University’s canine health center calls these soft, quiet sounds “innocent” or “physiologic” murmurs (Cornell). The Merck Veterinary Manual explains that many puppies have a low-grade murmur caused by mild turbulence in the blood, with no heart defect behind it.
| Source | When an innocent murmur goes away |
|---|---|
| VCA | May first appear at 6 to 8 weeks, and is usually outgrown by about 4 to 5 months |
| Cornell | Most are outgrown by 6 months of age |
| Merck | Usually disappears by 6 months of age |
An innocent murmur causes no symptoms, and the puppy grows and plays normally.
How vets grade a heart murmur in puppies
Vets grade a murmur by how loud it is. VCA describes a scale from I to VI.
| Grade | What the vet hears |
|---|---|
| I | Very soft, heard only now and then, in one spot on the chest |
| II | Soft, but heard every time |
| III | Moderately loud and easy to hear |
| IV | Loud, and heard over a wide area |
| V to VI | Very loud. At the top of the scale, it can be felt through the chest wall. |
VCA defines the two ends of the scale, and the middle grades fall in between. Innocent puppy murmurs sit at the low end. However, loudness alone does not settle the matter, so vets also note where and when in the heartbeat the sound occurs.
When a murmur points to a heart defect
A murmur present from birth can come from a structural problem. Merck lists the most common congenital heart defects in dogs:
- Patent ductus arteriosus (PDA)
- Pulmonic stenosis
- Aortic stenosis
- Persistent right aortic arch
- Ventricular septal defect
VCA notes that some of these, including subaortic stenosis, pulmonic stenosis and PDA, are hereditary. Therefore, a careful breeder has the parents’ hearts checked. See our guide to dog health testing before breeding.
A murmur is more worrying when it is loud, when it is still present after six months, or when the puppy has symptoms. Watch for tiring quickly, fast or labored breathing, coughing, fainting or slow growth.
Tests your vet may suggest
- Echocardiogram. This ultrasound of the heart is the key test. Cornell describes it as non-invasive and usually done without anesthesia or sedation.
- Chest X-rays, to see the size and shape of the heart and the lungs.
- Electrocardiogram, to record the heart’s rhythm.
- A recheck in a few weeks, which is often the first step for a soft murmur in a young, healthy puppy.
Treatment and outlook
The outlook depends entirely on the cause. VCA says it ranges from excellent to grave. An innocent murmur needs no treatment at all.
For a true defect, Merck notes that mildly affected dogs may show no ill effects and live a normal life span. More serious defects may be managed with medicine or corrected with a procedure. A veterinary cardiologist can tell you which applies.
What to ask a breeder about a heart murmur in puppies
Every puppy should have a vet exam before it goes home, and the vet listens to the heart at that visit. So ask:
- Did the vet hear a murmur? If so, what grade?
- Is it written in the health record?
- What happens if the murmur is still there at six months? Check the health guarantee in the puppy contract.
- Have the parents had their hearts checked?
A low-grade murmur at eight weeks is common, and it is not a reason to panic. Still, have your own vet listen at the first vet visit and again at each vaccine appointment. If you insure your puppy, read how pet insurance for puppies treats conditions noted before the policy starts.
Related guides
- Puppy Vaccine Schedule and Deworming: What Is Done Before Go-Home and What Comes Next
- Umbilical Hernia in Puppies: Is It Serious and Does It Need Surgery?
- Progressive Retinal Atrophy in Dogs: Signs, DNA Tests and Breeding
- Coccidia in Puppies: Signs, Treatment and Cleaning Up
- Heatstroke in Dogs: Warning Signs, First Aid and Prevention
See all our puppy guides, read about our health testing, or meet our Havapoo puppies for sale and Goldendoodle puppies for sale.
Sources
- VCA Animal Hospitals. Heart Murmurs in Dogs. vcahospitals.com
- Cornell University College of Veterinary Medicine. Get a jump on heart murmurs. vet.cornell.edu
- Merck Veterinary Manual. Congenital and Inherited Disorders of the Cardiovascular System in Dogs. merckvetmanual.com
Sources were checked on October 7, 2026. This article is general information and does not replace advice from your veterinarian.
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