Heart Murmurs in Cats

A heart murmur is an extra sound your vet hears with a stethoscope as blood moves through the heart or nearby vessels. In cats, that sound can happen for several reasons. Some murmurs are harmless and may come and go with stress, excitement, or a fast heart rate. Others are clues that a cat may have heart disease, a congenital heart defect, anemia, hyperthyroidism, or another medical problem affecting blood flow.

One important point for pet parents is that a murmur is not a diagnosis by itself. The loudness of the murmur does not always match how serious the underlying problem is. Some cats with significant heart disease have soft murmurs or no murmur at all, while some cats with louder murmurs may not have severe disease. Because of that, your vet usually looks at the whole picture, including age, symptoms, exam findings, blood pressure, lab work, and often heart imaging.

In adult cats, cardiomyopathy is the most common heart disease linked with murmurs, especially hypertrophic cardiomyopathy. In kittens, congenital defects such as valve abnormalities or septal defects are more likely. Many cats feel normal early on, so a murmur is often found during a routine wellness visit rather than after obvious illness starts.

The good news is that many cats with murmurs do well, especially when the cause is mild or when heart disease is found before heart failure develops. The next step is not to panic, but to work with your vet to decide how much testing is appropriate and how closely your cat should be monitored.

Diagnosis starts with a careful physical exam. Your vet listens to the heart to confirm that the sound is truly a murmur and may describe its timing and grade. They will also check heart rate, rhythm, pulses, breathing pattern, gum color, and whether there are signs of fluid in the chest or lungs. Even so, a stethoscope alone usually cannot tell whether a murmur is harmless or caused by significant heart disease.

Basic testing often includes blood work and blood pressure measurement. Lab work can help look for anemia, hyperthyroidism, kidney disease, or other conditions that may contribute to a murmur or affect treatment choices. Some vets also use NT-proBNP or similar cardiac biomarker testing to help estimate whether heart muscle stretch is present, although this test does not replace imaging.

Chest X-rays can help assess heart size and look for fluid in or around the lungs. An electrocardiogram may be added if an arrhythmia is suspected. The most informative test in many cats is an echocardiogram, which is an ultrasound of the heart. This allows a veterinarian, often a cardiologist, to see chamber size, wall thickness, valve motion, blood flow patterns, and evidence of congenital defects or cardiomyopathy.

Not every cat needs every test on day one. A young kitten with a soft murmur may be monitored differently than an older cat with weight loss and fast breathing. Your vet can help match the workup to your cat's age, symptoms, exam findings, and your goals for care.

Heart murmurs happen when blood flow becomes turbulent. In cats, that turbulence may come from structural heart disease, changes in blood thickness, or temporary changes in heart rate and circulation. One of the most common causes in adult cats is cardiomyopathy, especially hypertrophic cardiomyopathy, which changes the thickness and function of the heart muscle. Some cats with cardiomyopathy have a murmur, while others do not.

Kittens may have murmurs from congenital heart defects such as malformed valves, septal defects, or narrowing at a valve. Some kitten murmurs are innocent and disappear as the kitten grows, but others reflect defects that need monitoring or referral. The murmur grade alone does not reliably tell which is which.

Secondary causes also matter. Hyperthyroidism can create or worsen a murmur and may contribute to changes in the heart muscle. Anemia can make blood flow sound more turbulent even when the heart itself is structurally normal. High blood pressure, fever, dehydration, and stress can also change what your vet hears during an exam.

Risk tends to rise with age for acquired heart disease, although young cats can also be affected. A history of thyroid disease, known hypertension, prior heart findings, or breed-related concern for cardiomyopathy may increase suspicion. Still, any cat with a murmur deserves an individualized assessment rather than assumptions based on age or breed alone.

Not every heart murmur can be prevented. Some are caused by inherited or congenital heart problems, and some adult heart diseases develop even in cats that appear healthy. Still, there are practical ways to lower the chance that a murmur will go unnoticed or be made worse by another condition.

Routine wellness exams are one of the most useful tools. Many murmurs are first found before a cat shows any outward signs. Regular visits give your vet a chance to compare heart sounds over time, check blood pressure, and recommend follow-up before a crisis develops. Senior cats especially benefit from screening for hyperthyroidism, kidney disease, and hypertension, since these conditions can affect the heart.

Good nutrition also matters. Commercial cat foods are formulated to provide taurine, an amino acid that is essential for heart health in cats. Homemade diets should only be used with veterinary nutrition guidance. Keeping your cat at a healthy body condition, reducing stress around vet visits when possible, and following through on recommended rechecks can also support earlier detection and steadier management.

For breeding cats or kittens from lines with known heart disease concerns, discussing screening with your vet is reasonable. Prevention is not always about stopping disease from happening. Often, it is about finding change early enough to give your cat more options.

Prognosis depends almost entirely on the cause of the murmur. Cats with innocent or stress-related murmurs may never develop heart problems and can live normal lives. Cats with mild structural disease may also do well for years with monitoring alone. In these cases, the murmur is more of a finding to track than a crisis.

When the murmur is linked to cardiomyopathy, the outlook varies widely. Some cats remain stable for a long time, especially if they have no signs of congestive heart failure or clot formation. Others may worsen over months or years, and some cats first present with an emergency such as breathing distress or a saddle thrombus. That range is one reason early follow-up matters even when a cat seems comfortable.

If congestive heart failure develops, the prognosis becomes more guarded and long-term medication is often needed. Cats that survive the initial crisis may still have meaningful quality time, but they usually need ongoing monitoring, repeat imaging, and medication adjustments. Cats with thromboembolism can recover partially or fully in some cases, but recurrence risk and overall heart status strongly affect the outlook.

Recovery after diagnosis is usually less about curing the murmur and more about managing the underlying condition. Your vet can help you understand what changes to watch for at home, how often rechecks are needed, and what level of care best fits your cat and your family.