What is a Heart Murmur in Cats?
A heart murmur in a cat is an abnormal “whooshing” or “swishing” sound that a veterinarian may hear when listening to the cat’s heart with a stethoscope.
This sound is caused by turbulent or irregular blood flow inside the heart or in the major vessels leaving the heart, unlike the normal “lub-dub” sound of a healthy heart.
Importantly, a murmur doesn’t always mean there is a severe disease. Some murmurs are “innocent” (harmless) or functional, while others may point to underlying health problems.
Why Does a Cat Develop a Heart Murmur?
There are multiple potential causes of heart murmurs in cats — some benign, others more serious.
• Congenital (present from birth)
- Some kittens are born with structural heart defects — for example, abnormal heart valves or holes in the heart wall (septal defects), like an atrial septal defect (ASD) or ventricular septal defect (VSD).
- In many of these cases, murmurs may be detected in early vet examinations shortly after birth.
• Acquired (developed later in life)
- Heart muscle diseases, such as Hypertrophic Cardiomyopathy (HCM) — the most common heart disease in cats — can cause murmurs.
- Problems with heart valves (valve insufficiencies or narrowing) or defects in large vessels may also lead to abnormal blood flow and a murmur.
• “Functional” or Non-cardiac Causes
- Some murmurs occur not because of structural heart disease, but as a result of “functional” issues. For example, anemia (low red blood cell count), dehydration, high blood pressure, metabolic problems, stress, fever, or illness may temporarily disturb blood flow and cause murmurs.
- In kittens, especially, these flow murmurs may disappear as they grow.
What Symptoms Should Cat Owners Watch For
Often, a murmur is found during a routine veterinary exam — especially if the cat seems healthy.
However, when a murmur reflects significant heart disease or progressing heart failure, these are common symptoms you might notice:
- Loss of appetite or reduced eating, and consequent weight loss.
- Lethargy, weakness, or reduced activity — the cat may sleep more, hide, or seem uninterested in usual play or movement.
- Difficulty breathing, panting with minimal effort, rapid breathing, coughing, or wheezing.
- Pale or discolored gums (sometimes bluish or greyish), or changes in gum color.
- In kittens with severe congenital defects, stunted growth, or failure to thrive.
- In extreme cases, sudden collapse, paralysis of hind limbs, or signs of pain or distress — especially if complications like blood clots develop.
Because cats are good at hiding illness, many symptoms might go unnoticed until the disease is advanced.
How Veterinarians Diagnose a Heart Murmur
Detection begins with a routine physical exam and listening to the cat's heart with a stethoscope.
If a murmur is heard, further tests are usually recommended to determine what’s behind it and whether it’s serious. Common diagnostic steps include:
- Blood tests to check for anemia, metabolic issues, or other systemic conditions.
- Chest X-ray (radiograph) to assess the size and shape of the heart, and to look for fluid in or around the lungs.
- Echocardiogram (ultrasound of the heart) — widely considered the “gold standard” for diagnosing structural heart problems.
- Sometimes, an electrocardiogram (ECG/EKG) is used to detect an abnormal heart rhythm.
Because the murmur's loudness (grade) does not always correlate with severity, diagnostic imaging is crucial.
Treatment and Management Options
A heart murmur itself is not treated — only the underlying cause (if any) should be addressed.
• When treatment may not be needed
- If the murmur is “innocent” or functional (e.g., due to anemia, stress, or a temporary state) — and if, after evaluation, no structural problems are found — the veterinarian may recommend monitoring only. Many such murmurs resolve on their own, especially in kittens.
• When medical treatment is necessary
- If diagnostic results reveal heart disease or another significant condition, your veterinarian may recommend medications that help the heart work more efficiently, reduce fluid accumulation, and improve overall blood circulation. For example, diuretics, ACE inhibitors, anti-clotting medications, or other cardiac drugs, depending on the condition (e.g., Restrictive Cardiomyopathy or HCM).
- In cases of severe structural defects (like patent ductus arteriosus (PDA) or severe septal defects), surgical intervention may be considered.
• Long-term care and monitoring
- Regular checkups with a veterinarian — including periodic blood work, X-rays, or ultrasounds — are vital for tracking the cat’s condition and adjusting treatment as needed.
- Monitor for changes in appetite, weight, breathing, activity level, and other symptoms that could indicate worsening heart disease.
With early detection and careful care, many cats with heart murmurs — even those with severe underlying conditions — can live for many years.
What Every Cat Owner Should Know
- A heart murmur is not always a cause for panic. Some murmurs are harmless and may never affect the cat’s quality of life.
- Because heart murmurs vary widely in cause and severity, only an accurate veterinary diagnosis — often including an echocardiogram — can determine whether a heart murmur is severe.
- Cats are good at hiding illness. Owners should pay close attention to subtle signs, such as reduced activity, poor appetite, weight changes, breathing difficulty, pale gums, or reluctance to play.
- Timely veterinary care and regular check-ups are key — especially if your cat is middle-aged or older, or belongs to a breed prone to heart disease.
Conclusion
A heart murmur in a cat signals an irregular heart sound caused by turbulent blood flow — but it doesn’t always mean severe disease. Understanding the possible causes, symptoms, and importance of proper veterinary diagnosis is critical.
If your cat is diagnosed with a murmur, work with your vet to determine the underlying cause. With accurate diagnosis, appropriate treatment, and ongoing care, many cats go on to live comfortable, happy lives.
Regular wellness checks — especially for middle-aged or senior cats — remain the best way to detect problems early and ensure your feline friend stays healthy for years to come.
