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Heart Disease & Heart Murmurs in Cats

Est. read time: 8 min.

February is Cat Health Month and American Heart Month. So, let’s discuss heart disease in cats and heart murmurs in cats. If your cat was just diagnosed with a heart murmur, here’s what you need to know:

It’s not normal for a cat to have a heart murmur.

So, what is a heart murmur, and does my cat’s heart murmur need to be treated?

Recognizing heart murmurs in cats

First, how does your veterinarian diagnose a heart murmur? One of the reasons why I’m such an advocate for a yearly veterinary examination is because I want to “lay my hands” on your cat and do a thorough physical examination. Part of my exam is auscultating (or “listening”) to the heart and lungs using my stethoscope—I’m actually listening for an abnormal sound and rhythm. You might see your veterinarian listening between your cat’s armpit area. That’s because, anatomically, the heart sits near the front part of the chest cavity (in the area of the third to fifth rib spaces). 

So, what are we listening for? When we listen to the heart, it should be a normal, clear, crisp heart beat. There shouldn’t be any unusual “whooshing” sound. If I do hear this “swishing” or “whooshing” sound, it’s consistent with a heart murmur.

The next thing I’m listening for is the heart rate and to see if there is a heart arrhythmia, which is an abnormal rhythm of the heart. In cats, the heart rate should range from 160-220 beats per minute (bpm). (While this sounds really fast, it’s because a lot of cats are excited or nervous at the veterinary clinic. At home, your cat’s resting heart rate should be around 140-160 bpm.) If you can imagine a metronome, the cat’s heart should be a consistent, fast beat-beat-beat-beat rhythm. If your cat has a heart arrhythmia, it means there’s an unusual pattern to the beat, like a beat-beat-pause-beat-beat-beat-pause. Sometimes, cats will have a heart arrhythmia called a “gallop,” named after the sound of a galloping horse. Regardless, a cat should not have a heart murmur or a heart arrhythmia. 

How heart murmurs in cats are “graded”

In veterinary medicine, heart murmurs are graded on a scale of 1-6, with 6 being the loudest, and 1 being the softest. Sometimes, a heart murmur and/or arrhythmia may be innocent and may not be caused by primary disease. Sometimes we can hear it from pain, nervousness, dehydration, or anemia; this typically is a soft (e.g., 1 or 2/6 heart murmur). But sometimes heart murmurs and/or arrhythmias can be caused by primary heart disease or defects/malformations (e.g., > 3/6 heart murmur). This is much more serious, as it can result in congestive heart failure, acute stroke, and death.

Unfortunately, cats can be frustrating when it comes to diagnosing heart disease. It’s estimated that 50% of cats with significant heart disease (or even heart failure) don’t have a heart murmur that we can detect with our stethoscopes. Confusing, but the point is, if a heart murmur and/or arrhythmia is heard, it warrants a workup.

Why age of diagnosis matters

What age your cat was diagnosed with a heart murmur is going to affect how aggressively I recommend a veterinary workup with a board-certified veterinary cardiologist. If your kitten is diagnosed with a heart murmur early, this must be rechecked frequently! If the heart murmur doesn’t go away after a few weeks, a more extensive medical workup is imperative, as the heart murmur is often from a congenital cause. Congenital means that the kitten was born with a defect, which may be due to poor nutrition, medication or drug exposure, environmental conditions, infections, poisonings, or most commonly, inherited reasons. A defect in the heart—which ranges from holes in the heart (e.g., atrial or ventricular septal defect) to valve defects (e.g., valve dysplasia) to abnormal narrowing of parts of the heart or major blood vessels (e.g., patent ductus arteriosus, aortic stenosis, etc.) can be deadly without diagnosis and treatment.

The sooner we diagnose a heart murmur condition in a kitten, the sooner we can intervene and treat it. I should know, as the cat I adopted years ago had a severe congenital heart defect (with a 6 out of 6 heart murmur), and only survived to 3 years of age. 

So, what if your healthy cat just happens to be diagnosed while visiting your veterinarian for his or her routine veterinary exam, and isn’t showing any symptoms? Well, as your cat ages, it’s important to know if the heart murmur is getting louder and louder—like going from a 2/6 one year to a 3/6 the next year. If it is, a workup is a must. 

Causes of heart disease in cats

The most common types of primary heart disease in cats (excluding congenital causes) include:

  • Hypertrophic cardiomyopathy (HCM)
  • Dilated cardiomyopathy (DCM)
  • Restrictive cardiomyopathy (RCM)
  • Unclassified cardiomyopathy (UCM)

With HCM, the heart muscle becomes too thickened. With DCM, the heart muscle becomes too “floppy” and loses its ability to contract. DCM is often linked to taurine deficiency, a key amino acid necessary in cat food. (That’s one of the reasons why I’m a strong proponent for an AAFCO-approved, balanced cat food.) With RCM, there’s too much scar tissue or fibrosis in the ventricle, preventing the heart from beating efficiently. Unclassified cardiomyopathy means that there are cardiac abnormalities, but they don’t fit into one of the above categories.

As for secondary causes, know that heart murmurs can be seen in cats from certain medical conditions like hyperthyroidism (an overactive thyroid gland), chronic anemia, or hypertension. If your cat is diagnosed with one of these conditions, medical treatment is really important. Otherwise, your cat can die of other complications or have long-term side effects from it (like heart failure)!

Signs of heart disease in cats

Signs of heart disease in cats include:

  • Pale gums 
  • An increased respiratory rate
  • Open mouth breathing
  • A racing heart rate 
  • Collapse
  • Sudden paralysis of the hindlegs (called a saddle thrombus)
  • Crying out in pain
  • Inability to walk
  • Fainting
  • Sudden death

Working up heart murmurs in cats

Workup of a heart murmur includes a thorough physical examination, focusing especially on the thyroid gland, pulses, kidney size, and bladder. It’s going to include a blood pressure, routine blood work (to rule out the above medical problems), and X-rays of the chest and lungs. Depending on what these tests show, the next step may be referral to a board-certified veterinary cardiologist for an echocardiogram (ultrasound) of the heart. These typically cost about $500-$800 for the ultrasound and examination fee, but are really important to determine if your cat has a life-threatening type of heart disease. 

Depending on what these results show, your cat may need to be started on heart medications that make your cat’s heart beat more efficiently. Even with treatment, heart disease can ultimately result in heart failure and secondary fluid backing up directly into the lung (what we call pulmonary edema) or outside of the lung into the chest cavity (called pleural effusion). Both of these can be life-threatening and result in congestive heart failure.

Treating heart murmurs in cats

When it comes to heart murmurs in cats, keep in mind that the sooner we diagnose it, the sooner we can start your cat on the correct medications to make the heart beat more efficiently and to prevent congestive heart failure. Some of these medications may include:

  • Beta-blockers to slow down the heart rate
  • Calcium channel blockers to relax the heart and lower blood pressure
  • Diuretics to prevent fluid from accumulating in the lungs or chest
  • Angiotensin-converting enzyme (ACE) inhibitors to help the heart beat more efficiently and treat hypertension
  • Anti-stroke medications like aspirin or clopidogrel

Keep in mind that these medications don’t CURE heart disease in cats. Instead, they help prevent the heart disease from getting worse. 


Which type of heart disease your cat has and how severe the findings are on the ultrasound of the heart will affect your cat’s prognosis. When in doubt, talk to your veterinarian about long-term management and working your cat up for the heart murmur. Most importantly, prevention of heart murmurs in cats and heart disease in cats through annual veterinary examinations is a must!

Photo by Stephanie Legler on Unsplash

tabby cat on red blanket - heart disease and heart murmurs in cats


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