A heart murmur in cats is an abnormal heart sound caused by changes in blood flow. Some murmurs are harmless, while others may signal heart disease or another medical condition. A veterinary exam and diagnostic testing help determine whether treatment or monitoring is needed.
This guide explains why heart murmurs occur, how veterinarians evaluate them, and what the next steps usually look like for your cat’s health.
Is a heart murmur in cats always serious?
A heart murmur is not a diagnosis on its own. A murmur refers to an abnormal heart sound heard when your veterinarian listens to the chest wall. This sound comes from turbulent blood flow inside the cat’s heart. Many cats with a heart murmur feel completely normal and show no outward signs of illness. Others may have a clinically significant heart murmur linked to heart disease or another underlying issue.
Your veterinarian looks at more than the sound alone. Age, history, physical exam findings, and your cat’s condition all matter. A murmur can still be linked to severe heart disease, while quite loud murmurs can sometimes come from relatively small defects or temporary changes in blood flow. The sound helps guide the next steps, but it does not explain the full condition on its own.
What a heart murmur is and why it happens
A heart murmur is an abnormal sound caused by changes in how blood moves through the heart chambers, heart valves, heart muscle, or the large vessels exiting the heart. In a healthy heart, blood flow is smooth and quiet. When flow becomes uneven, it creates an abnormal noise that your veterinarian hears with a stethoscope. This change in blood flow may happen because of:
- Structural changes in the heart
- Problems with the heart valves
- Changes in blood thickness or speed
- Conditions outside the heart that affect circulation
The murmur itself is not painful. Listening to the heart is completely painless, and your cat is awake and conscious during the exam.
Murmur grading and what “loud” means
Veterinarians use a grading system, sometimes called a chest grade, to describe how loud the murmur sounds. Louder murmurs do not always indicate more severe disease. Some loud murmurs come from small changes that do not limit heart function, while serious cardiac disease can sometimes produce a softer sound.
Note that loudness is only one piece of information. Your veterinarian also considers rhythm, timing, location, and whether the abnormal sound is constant or only heard intermittently during the exam.
Innocent heart murmurs and clinically significant murmurs
Not all murmurs are linked to disease. An innocent murmur, sometimes called a physiologic murmur, occurs when blood flow changes without evidence of structural heart disease. These are more common in young kittens and may resolve as they grow. Some healthy adult cats may also have a soft murmur with no heart damage.
A clinically significant heart murmur suggests an underlying heart problem or another medical condition that affects circulation. These murmurs often lead to further testing, especially in older cats or adult cats with new findings.
A soft or inconsistent heart sound may be present during one exam and not the next. This can occur due to stress, hydration levels, or blood flow changes. Rechecks help determine if the finding is consistent or temporary.
Common causes of a feline heart murmur
A feline heart murmur can be linked to heart-related or non-heart-related causes.
Heart-related causes
Some heart sounds are linked to cardiac disease, including:
- Hypertrophic cardiomyopathy, a condition where the heart muscle thickens
- Congenital heart disease, present from birth
- Ventricular septal defect, a small opening between the heart chambers
- Other forms of structural heart disease
- Acquired heart disease that develops later in life
These conditions affect how the pet’s heart pumps blood and may progress over time.
Causes outside the heart
A murmur may also result from an underlying disease that changes blood flow, such as anemia or thyroid disorders. In these cases, treating the underlying cause can reduce or resolve the murmur.
Symptoms and clinical signs to watch for
Many cats with a murmur show no signs at first. When symptoms do appear, they usually reflect increased strain on the heart or changes in circulation.
Common symptoms include:
- Breathing problems or rapid breathing at rest
- Poor appetite
- Weight loss
- Low energy
- Pale gums
More severe signs may indicate heart failure or congestive heart failure, where fluid builds up around the lungs. These cases need prompt care.
How veterinarians confirm what is happening
A murmur usually leads to diagnostic testing to understand the underlying heart condition and guide care.
Cardiac ultrasound and heart scans
A cardiac ultrasound examination, often called a heart scan, allows your veterinarian to see heart size, motion, and blood flow in real time. A detailed ultrasound examination helps identify valve problems, muscle thickness, chamber size, and blood flow direction.
Additional testing
Other further tests may include:
- Blood tests to look for anemia or other medical causes
- Chest X-rays to check heart size and lungs
- Blood pressure checks
- Electrocardiograms for rhythm assessment
These tests work together to identify the underlying issue and determine whether the murmur is incidental or linked to disease.
Prognosis and long-term outlook
Prognosis can vary widely. Some cats with incidental heart murmurs live normal lives without limits. Others with severe heart conditions may need long-term treatment and close follow-up. The long-term prognosis depends on the cause, response to treatment, and your cat’s overall health. Early evaluation and consistent monitoring help support stable outcomes for many cats.
What your cat experiences during exams
Heart exams are calm and brief. Your cat remains awake, handled gently, and monitored for comfort. Most diagnostic steps are noninvasive, and your veterinarian works to reduce stress during each visit.
Questions you can ask your veterinarian
Clear communication helps you make informed choices. You may ask:
- Is this murmur likely innocent or clinically significant?
- Do you recommend a cardiac ultrasound now or monitoring first?
- Are blood tests needed to rule out an underlying disease?
- What changes at home should I watch for?
Conclusion
If a murmur is found or if your cat shows signs such as breathing changes, poor appetite, or weight loss, a timely exam is the next step. Care guided by experience and clear testing supports your cat’s health over time.
For families looking for clear guidance and consistent care, Ridgefield Veterinary Center has supported cats and their owners for decades with a thoughtful, thorough approach to heart findings and overall wellness. Schedule an exam to discuss your cat’s heart health with our veterinary team.
FAQs
What is the life expectancy of a cat with a heart murmur?
It depends on the cause. If your cat has an innocent heart murmur or a stable condition, life expectancy may be normal. Cats with clinically significant heart murmurs or diseases like hypertrophic cardiomyopathy can also live for years with the right treatment plan and regular care. Prognosis ranges vary, but many cats do well with follow-up.
What can be done for a cat with a heart murmur?
Your veterinarian will recommend diagnostic testing, such as a cardiac ultrasound examination or blood tests, to find the underlying cause. Treatment depends on the diagnosis. Some cats need only periodic examinations. Others may need medication for congestive heart failure, blood pressure control, or another underlying heart condition.
What is the most common cause of heart murmurs in cats?
The most common cause is hypertrophic cardiomyopathy, a type of structural heart disease where the heart muscle becomes abnormally thick. Other causes include congenital heart disease, acquired heart disease, anemia, and hyperthyroidism. Some murmurs are incidental findings with no disease present.
Does a heart murmur hurt cats?
No. A heart murmur is a sound and not a painful event. It’s completely painless and often found during a routine exam. However, if it’s linked to severe heart disease, symptoms like breathing problems or poor appetite can affect your cat’s health. The murmur itself doesn’t hurt, but what’s causing it might require treatment.