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Is a Grade 1 heart murmur common in puppies? Will they outgrow it?

Updated on September 23rd, 2025

Pet's info: Dog | Norwich Terrier | Male | neutered

We are about to adopt a puppy (small breed), who we found out has a Grade 1 heart murmur. We are told that the puppy may grow out of it entirely, it may stay stable, or it may progress. How common is this situation? What research or statistics are available for us what could happen?

2 Answers

Most Helpful Answer

Answered By Dr. Davis

Veterinarian

Published on August 8th, 2017

This is common and generally they do grow out of it. Norwich Terriers are not at high risk for heat disease. I don't know of any statistics on this. If the murmur persists a grade 1/6 is very mild and would not require treatment. Generally a grade 3 or higher may need medication to improve the heart function and reduce fluid in the lungs. Most dogs with heart murmurs live long lives with minimal issues. Personally I would adopt the puppy anyway as I would not expect it to progress or effect the dogs quality of life. To be safe you may want another veterinarian to examine the pup and listen also. It's always a good idea to get a second opinion. Thanks for using Petco Pet Education Center, formerly Petcoach to help you get answers to your veterinary questions.

1Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Dr. Macartney, BVet Med, MRCVS
Veterinarian
It is very common for young puppies, especially large breed puppies, to develop an innocent heart murmur while they are growing rapidly. The murmur may first appear at 6-8 weeks of age, and a puppy with an innocent heart murmur will usually outgrow it by about 4-5 months of age. This type of murmur is benign.

If the puppy is over 4/5 months of age and the murmur is still present then it is most likely not an innocent murmur.

I would start with a blood test in the puppy. With young puppies, anemia and/or hypoproteinemia can be caused by a heavy infestation of parasites such as intestinal worms, blood parasites, fleas or ticks. These can lead to murmurs.

The next step would be an echocardiogram, or an ultrasound of the heart to monitor how it is functioning and its structure.

There are several congenital heart defects in puppies. They would be identified using this diagnostic tool. The three most common types of defects are;

PATENT DUCTUS ARTERIOSUS
PULMONIC STENOSIS
SUBAORTUC STENOSIS

Each has its own treatment option and prognosis. Each would be identified after the puppy is over 5 months using a echocardiogram.
0Pet Parents found this answer helpful

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