How to Identify a Heart Murmur in Cats

Few of us think much about our hearts. That’s because they usually goes about their jobs, day in and day out. 

So, if we’ve thought so little about our own hearts, there’s a decent chance we’ve thought even less about our cats’. We don’t think about it, that is, until something is wrong. One such issue is a heart murmur. This diagnosis can be confusing and scary, so let’s take some of the questions out of it.

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What is a heart murmur in cats?

When your vet listens to your cat’s heartbeat, they expect to hear two noises that indicate that blood is flowing as it should through their heart. A healthy heartbeat creates a unique “lub dub” sound: the “lub” is brought about by the closure of the valves that separate the upper atrial chambers of the heart from the lower ventricular chambers, and the “dub” is the sound of the valves to the lungs and the body closing as blood is pumped from the ventricles outward. 

Now, if your cat’s heart is producing an extra whooshing sound along with the “lub dub,” it’s called a murmur. This extra sound happens when blood is moving somewhere out of the ordinary when the heart beats and can be due to a number of different changes in either the heart itself or something outside of this all-important organ.

Symptoms of heart murmurs in cats

A little extra noise in the heart isn’t going to make much difference in your cat’s day-to-day life, and you definitely won’t be able to hear it with a naked ear. But, if your cat’s heart murmur is due to a progressive issue with the heart, they may start to show symptoms as things get worse and worse. Signs you may see include:

• Increased lethargy

• Weakness, collapse

• Weight loss

• Decreased appetite

• Pale gums

• Coughing or wheezing

• Exercise intolerance

• Difficulty breathing

• Stunted growth in kittens

Most mild heart murmurs will be diagnosed by your veterinarian during a routine checkup, but if you notice any of these changes in your cat, see your veterinarian instead of waiting for their next visit.

Causes of heart murmurs in cats

There are a few main causes of heart murmurs in cats, some of which are more serious than others.

Innocent heart murmur

Innocent heart murmurs are merely sounds that tend to show up intermittently. They may occur when a cat’s heart rate is sped up due to stress, or they may happen for a short time while a kitten is growing rapidly. These heart murmurs can’t be heard when the heart rate returns to normal or a kitten will often grow out of it. They tend to be mild and don’t cause any other signs.

Structural heart murmurs

Sometimes the extra noise is due to a structural defect in the heart. In normal blood flow, blood flows from the body into the right atrium, through a valve to the right ventricle through a valve into the lungs, back into the left atrium, through a valve to the left ventricle and then through a valve out into the body. That’s a lot of plumbing within which a problem can arise.

Leakiness in the valves, a thickening or constriction of a valve or vessel, or a hole in any of the chamber walls can contribute to extra noise as blood flows through. Young animals are more likely to experience a heart murmur due to a congenital defect or hole in the walls of the chambers or a mix-up in the blood vessels. Older cats are more likely to develop a cardiomyopathy that causes a leaky valve or other changes in the heart muscle.

Some cat breeds are predisposed to developing heart murmurs as a result of conditions such as hypertrophic cardiomyopathy or dilated cardiomyopathy. So, if you have a Siamese, Persian, Ragdoll, or Maine Coon, make sure you see your vet regularly to stay on top of these potential heart conditions.

Extracardiac murmurs

These are the causes of heart murmurs that are outside the heart’s control, such as anemia or low blood protein caused by blood loss due to an injury or parasites. Hyperthyroidism, heartworms, pregnancy, obesity, high blood pressure, and infections can also be to blame.

Dental infections can lead to heart issues; bacteria from the mouth can set up shop in the heart valves, causing leakiness and murmurs. So, if bad breath isn’t enough of a reason to keep your cat’s mouth clean, heart disease is.

Heart murmur treatment in cats

Listening alone can’t determine if your cat’s extra heart sounds are an innocent finding or due to something more serious. Instead, your vet will need to roll up their diagnostic sleeves and really dive in to understand where this extra noise is coming from and if they should do anything about it.

How heart murmurs are diagnosed in cats

Listening may be useful in determining where the sound is coming from and its intensity, but blood work and imaging are where the diagnosis lies. Blood work will help rule out extra cardiac causes while imaging will help your vet get a look at the heart. X-rays will provide a visual of the heart’s size and check for any lung involvement. An ultrasound of the heart, called an echocardiogram, will provide further information about the heart’s valves, chambers, and vessels.

Treatment for heart murmurs in cats

Diagnosing the cause of the heart murmur is the first step in treatment. That’s because the murmur itself isn’t what’s being treated, but the underlying cause. Cats with innocent heart murmurs typically don’t require any treatment as the murmur will resolve with a reduction in stress or they will grow out of it.

For some cats, treatment means medications and/or a diet change to treat things like hyperthyroidism, high blood pressure, and anemia. Medications and diet may also help some cardiac causes of heart murmurs as well as help manage the output of the heart.

Some congenital causes may require surgery to repair, and causes of heart failure may require medications, oxygen therapy, and fluid removal from the lungs.

When to seek expert help

For most kitties, their heart murmur will be diagnosed by a vet during a routine checkup, so expert help has already been sought so to speak. For other cats, you may not know there’s a problem until things get severe enough to start producing symptoms.

So, if your cat starts showing signs of exercise intolerance, coughing, weight loss, difficulty breathing, pale gums, etc., don’t merely attribute it to aging; see your veterinarian instead. The sooner a heart murmur is diagnosed, the better the outcome for treatment.

References

• “Congenital Heart Disorders.” Cornell Feline Health Center. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/congenital-heart-disorders.

• “Heart Disease-Cats.” Tufts Cummings School of Veterinary Medicine. https://vet.tufts.edu/foster-hospital-small-animals/specialty-services/cardiology/heartsmart/heart-disease-cats.

• “Prevalence and Clinical Significance of Heart Murmurs Detected on Cardiac Auscultation in 856 Cats.” Veterinary Sciences. 13 Oct 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC9611806/.

• “When to Worry About Murmurs.” University of Illinois College of Veterinary Medicine. 7 Jul 2020. https://vetmed.illinois.edu/2020/07/07/when-to-worry-about-murmurs/.