What to Do if Your New Puppy Has a Heart Murmur

No one wants to hear that their cute little new puppy has a heart issue. But with some proactive pet-parenting, this often will not impact their life span. While many puppy heart murmurs will likely resolve on their own as a dog grows, others can indicate underlying heart problems. These heart problems may require additional testing, careful monitoring, and perhaps even medications or lifestyle adaptations to manage or treat them. Consistently visiting a veterinarian who can detect changes in, or spot concerns with, your puppy’s heart can greatly help put your new puppy on a track a good health.

What is a canine heart murmur? 

When you listen to a normal heartbeat using a stethoscope, you will hear the classic “lub-dub” sounds of the heart valves closing. If a dog has a heart murmur though, you will also hear a “whoosh” or “swish” sound in addition to the “lub-dub.” This extra sound is the “murmur” and there are a few causes for this. 

Causes of heart murmurs in dogs

A heart murmur is the sound of blood flowing turbulently through the heart valves, but what causes heart murmurs in dogs can vary. The majority of heart murmurs in puppies are due to your puppy having a low percentage of red blood cells (i.e. anemia). A more serious type of heart murmur can be due to a structural defect in your puppy’s heart that they are born with. The third type of heart murmur is due to heart disease that affects the heart valves or muscles and is diagnosed as your dog ages.

How heart murmurs impact a dog’s life expectancy

Dogs with heart murmurs can live long lives, especially if the condition is caught early, or if it is the type they outgrow. If a heart murmur is not of the type that your dog can outgrow, your veterinarian may recommend dietary and lifestyle changes to help support, and not stress, your dog’s heart. 

As your dog ages, medications may be needed if the murmur worsens. These medications can prolong your dog’s life but their life expectancy will depend on the reason for the heart murmur, the severity of the murmur, and how early the heart murmur was caught. If your puppy has a heart murmur that they outgrow though, it will not affect their life expectancy.

Do puppy heart murmurs go away? 

Yes, most heart murmurs in puppies go away by the time your puppy is six months old. If you’re wondering if heart murmurs are common in puppies, you’ll be relieved to know that while it is very dependent on the breed, an average of 28 percent of puppies have heart murmurs (which most puppies will outgrow). But how serious is a heart murmur in a puppy? Thankfully only about one percent of puppies are born with heart murmurs caused by serious heart defects, and won’t go away. 

Types of heart murmurs in puppies 

Identifying the type of heart murmur that your puppy has will help determine what you need to do next, or if this is something your puppy will outgrow. There are three main types of heart murmurs in dogs which are defined by when they appear, the cause, and the murmur’s severity “grade” on a scale of I to VI. If the murmur is caused by heart disease, there are also five stages of heart disease (A, B1, B2, C, and D) that are defined by the progression of that disease.

Innocent murmurs 

Physiologic or functional heart murmurs are slight heart murmurs in puppy heartbeats that are of no concern. Your puppy will outgrow these murmurs, which are due to a low red blood cell percentage. They are usually given low grades of I or II and assigned a heart disease stage B1. As red blood cell percentages increase, the heart murmur will go away. 

Adult dogs can also have physiologic or functional heart murmurs due to various conditions including anemia, fever, pregnancy, and hyperthyroidism. These heart murmurs can go away if the underlying cause resolves itself, or if the dog gets the proper treatment.

Congenital murmurs 

Some puppies have congenital murmurs because of a structural defect in their hearts. These murmurs do not go away like innocent, functional, or physiologic murmurs and require lifelong treatment. Pulmonic stenosis (PS) is the most common congenital, structural heart defect followed by patent ductus arteriosus (PDA), subaortic stenosis (SAS), and ventricular septal defect (VSD). These murmurs can be a grade I, II, III, IV, V, or VI depending on the severity of the murmur and the heart disease may progress from stage B1, to B2, to C, to D over time.

Acquired murmurs

Acquired murmurs may reveal themselves after a puppy is born. These murmurs develop over your dog’s life — and are not something they have when they are young. Heart valve and muscle diseases typically cause acquired murmurs. These murmurs can be a grade I, II, III, IV, V, or VI depending on the severity of the murmur, and the heart disease may progress from stage B1, to B2, to C, to D over time.

Heart murmur symptoms in dogs 

While dogs with low-grade heart murmurs typically don’t show any symptoms, more severe heart murmurs might cause noticeable issues in your dog.

Irregular heartbeat or racing pulse

Various heart issues that cause heart murmurs may also make your dog’s heart race. If the heart murmur is severe enough, you may even be able to feel an irregular heartbeat when you place your hand on your dog’s chest. However, a fast or irregular heartbeat is usually only noticeable when your dog is at the animal hospital.

Lack of energy

The heart is responsible for pumping oxygenated blood throughout your dog’s body. If a heart murmur is making it difficult for the heart to properly work, or if your dog has anemia, your dog may lack energy. 

Persistent cough

Heart disease that comes with heart murmurs may also cause coughing if the heart is enlarged or if there is fluid buildup around the heart from the disease. 

Collapse or fainting

Lacking energy, a dog with a severe heart murmur may collapse or faint. This is due to a heart issue, rendering the organ unable to pump enough oxygenated blood through the body, or because of severe anemia.

Bluish gums or tongue

For the same reasons a heart murmur can cause a lack of energy or fainting, a severe heart issue can also cause your dog’s gums or tongue to look blue. This is due to a lack of oxygenation.

Treatment for dog heart murmurs

Depending on the reason for the heart murmur, treatment can vary from simply waiting for the murmurs to stop on their own to lifelong medication.

Management strategies for puppies 

Innocent or physiologic murmurs typically disappear as your puppy’s red blood cell percentage increases. And physiologic murmurs in adult dogs will disappear as the underlying cause resolves itself naturally or with treatment. 

Congenital and acquired murmurs, on the other hand, require lifelong management and treatment. Activity restriction, dietary support, and regular heart monitoring may be recommended as initial management strategies for puppies with murmurs. 

Medical intervention 

If a heart murmur persists or worsens after your puppy is six months old — or your older dog is diagnosed with an acquired murmur — medications may be necessary to manage the underlying reason for the heart murmur. Your veterinarian may not recommend medications until your dog shows specific symptoms. This means regular monitoring of your dog’s heart health is vital.

Emerging research

A variety of research has been done (and is continuing to be done) on canine heart murmurs. Some of this research is related to how diets affect the heart. Other research is specific to certain dog breeds, looking for genetic links to heart murmurs. Additional research is being done to develop medications to treat, and even delay, heart disease that can cause murmurs.

Commonly asked questions

Can a puppy with a heart murmur live a normal life? 

Yes, puppies who are diagnosed with a heart murmur often outgrow their murmurs and live a normal life. However, a small number of puppies with heart murmurs have them because of a structural defect in their hearts. Or they will develop heart disease and require regular monitoring. Depending on the severity of the heart murmur and the underlying reason for it, medications, foods, or lifestyle changes may be needed to help manage your dog’s disease.

Are certain breeds more prone to heart murmurs? 

Yes, unfortunately, several dog breeds are prone to being born with or developing heart murmurs, especially large breeds. The breeds most commonly affected by heart diseases that cause murmurs include Airedales, Basset Hounds, Boxers, Cavalier King Charles Spaniels, Chihuahuas, Great Danes, Keeshonds, Maltese, Miniature Schnauzers, Newfoundlands, Poodles, Pomeranians, Yorkshire Terriers, West Highland White Terriers, and more.

References

Detecting and Recording Cardiac Murmurs in Clinically Healthy Puppies

FDA Conditionally Approves First Drug to Delay Onset of Congestive Heart Failure in Dogs

FDA Investigation into Potential Link Between Certain Diets and Canine Dilated Cardiomyopathy

Get a Jump on Heart Murmurs

Identification and Clinical Significance of Heart Murmurs in Puppies Involved in Puppy Trade

Innocent Cardiac Murmur in Puppies: Prevalence, Correlation with Hematocrit, and Auscultation Characteristics

The Tell-Tale Murmur: Heart Problems in Puppies