Heart Murmurs in Cats: When a sound on exam means more than stress
A heart murmur is a sound, not a final diagnosis. It tells the veterinarian that blood flow has become turbulent enough to hear with a stethoscope, but it does not yet explain whether the cat has a normal heart under stress, a congenital defect, cardiomyopathy, anemia, high blood pressure, or another problem entirely. Cornell’s heart-disease guidance emphasizes that serious feline heart disease can stay hidden for a long time, and hypertrophic cardiomyopathy remains the most common heart disease of cats (Cornell Feline Health Center, n.d.-a; Cornell Feline Health Center, n.d.-b). That is why one newly discovered murmur can lead to nothing more than watchful follow-up in one cat and a full cardiology workup in another.
At-a-glance guide
| Question | Fast takeaway |
|---|---|
| What exactly is your veterinarian hearing when they call it a heart murmur? | A murmur is the sound of turbulent blood flow moving through the heart or great vessels rather than the softer, cleaner sound of normal laminar flow |
| Can stress or excitement really create a murmur in an otherwise normal cat? | Yes, sometimes |
| Which diseases are veterinarians most worried about when a cat has a murmur? | Hypertrophic cardiomyopathy is a major concern because it is the most common heart disease in cats and may be present even in cats that look normal at home |
| What signs at home make a murmur more urgent rather than incidental? | Some cats with important murmurs show no signs at all, which is why follow-up still matters |
| How do veterinarians figure out whether a murmur is harmless, temporary, or serious? | The workup usually starts with the basics done well: a full physical examination, careful auscultation, blood pressure measurement when indicated, and bloo… |
| What usually happens after a murmur is confirmed on a workup? | If the murmur is functional and the rest of the evaluation is reassuring, the plan may simply be monitoring and recheck examinations |
What exactly is your veterinarian hearing when they call it a heart murmur?
A murmur is the sound of turbulent blood flow moving through the heart or great vessels rather than the softer, cleaner sound of normal laminar flow. It can be brief or persistent during the heartbeat, soft or loud, and located in different regions of the chest depending on the likely source. What it cannot do by itself is tell you whether the heart is structurally normal or diseased, which is why veterinarians treat the murmur as a finding that points toward a next step rather than a stand-alone explanation (Cornell Feline Health Center, n.d.-a).
That distinction is especially important in cats because a murmur may be absent even when serious heart disease exists, and present even when the heart turns out to be structurally normal. Cornell notes that stethoscope examination is cost-effective and valuable, but it cannot detect all feline heart disease (Cornell Feline Health Center, n.d.-a). So the murmur matters, but it always sits inside a bigger clinical picture made of age, symptoms, exam findings, and follow-up testing.
Can stress or excitement really create a murmur in an otherwise normal cat?
Yes, sometimes. Cats can develop so-called physiologic or functional murmurs when adrenaline is high and the heart is beating faster and more forcefully. That is one reason murmurs may be heard at a stressful veterinary visit and then sound different on recheck once the cat is calmer. But “maybe stress” is only safe shorthand after more serious causes have been considered, not before, because the same visit could also be revealing the first clue to heart muscle disease (Cornell Feline Health Center, n.d.-a).
Functional explanations also become less satisfying if the cat has any signs outside the stethoscope finding itself. Rapid breathing, poor appetite, fainting episodes, weakness, weight loss, or blood-pressure abnormalities push the case away from a simple stress story and toward a broader workup. Owners should think of stress as one possibility, not as the default answer that makes the murmur disappear clinically (Cornell Feline Health Center, n.d.-a; Cornell Feline Health Center, n.d.-c).
Quick decision path
Which diseases are veterinarians most worried about when a cat has a murmur?
Hypertrophic cardiomyopathy is a major concern because it is the most common heart disease in cats and may be present even in cats that look normal at home. Cornell explains that HCM thickens the muscular wall of the heart, reduces efficiency, and can contribute to congestive heart failure or thromboembolism in some patients (Cornell Feline Health Center, n.d.-b). A murmur may be part of that picture when altered blood flow develops inside the heart.
Murmurs can also occur with congenital defects, systemic hypertension, hyperthyroidism, anemia, or other high-output states that change how blood moves. Cornell’s feline health resources highlight both hypertension and hyperthyroidism as common disorders in older cats and both can interact with cardiovascular function in meaningful ways (Cornell Feline Health Center, n.d.-c; Cornell Feline Health Center, n.d.-d). That is why blood pressure and laboratory testing often matter almost as much as cardiac imaging.
What signs at home make a murmur more urgent rather than incidental?
Some cats with important murmurs show no signs at all, which is why follow-up still matters. But once a cat develops resting fast breathing, effortful breathing, sudden weakness, collapse, exercise intolerance, or a clear drop in appetite and activity, the conversation changes from “What is this sound?” to “Is this cat beginning to decompensate?” Cornell points out that serious heart disease can remain hidden until sudden decline, so owners should respect the first real change they see at home (Cornell Feline Health Center, n.d.-a).
Weight loss with a big appetite, agitation, or poor coat quality can also change the differential because they raise suspicion for hyperthyroidism, which itself can affect the heart. Likewise, an older cat with retinal problems or sudden blindness may fit a hypertension pattern rather than a purely primary heart problem. The murmur is therefore one clue in a network of clues, and the network is what determines urgency (Cornell Feline Health Center, n.d.-c; Cornell Feline Health Center, n.d.-d).
How do veterinarians figure out whether a murmur is harmless, temporary, or serious?
The workup usually starts with the basics done well: a full physical examination, careful auscultation, blood pressure measurement when indicated, and bloodwork to look for systemic disease. Cornell’s diagnosis guidance stresses the value of regular examinations because heart disease may otherwise stay hidden, and it frames the stethoscope exam as important but incomplete on its own (Cornell Feline Health Center, n.d.-a). This is one of those cases where a “normal-seeming cat” can still benefit from disciplined testing.
If the murmur persists, the cat has symptoms, or the veterinarian hears other concerning findings, echocardiography becomes the most useful next step. Cornell identifies echocardiography as the gold standard for diagnosing hypertrophic cardiomyopathy because it shows actual chamber and wall changes rather than inferring them from sound alone (Cornell Feline Health Center, n.d.-b). Depending on the case, electrocardiography, thoracic radiographs, and thyroid testing may also add important context.
What changes mean a cat with a murmur should be seen right away?
Seek prompt or emergency care if the cat develops open-mouth breathing, persistently fast breathing at rest, collapse, sudden weakness, fainting, blue or pale gums, or painful hind-limb dysfunction. Those are not “wait until the next wellness exam” signs, especially in a cat already known to have a murmur or another possible heart clue (Cornell Feline Health Center, n.d.-a; Cornell Feline Health Center, n.d.-b).
Also move faster if the murmur is new and the cat is losing weight, eating unusually, acting agitated, or showing blood-pressure-related warning signs such as vision changes. A murmur combined with systemic signs raises the chance that the real issue is bigger than the heart sound itself (Cornell Feline Health Center, n.d.-c; Cornell Feline Health Center, n.d.-d).
Bottom line
A heart murmur in a cat is best understood as a clue that needs context. Sometimes the clue leads to a normal heart under stress. Sometimes it is the first audible sign of heart muscle disease or another medical problem altering blood flow. The safest approach is to take the finding seriously without panicking: follow through on the workup, watch for breathing or circulation changes, and remember that in cats, subtle symptoms often matter more than dramatic ones (Cornell Feline Health Center, n.d.-a).
What usually happens after a murmur is confirmed on a workup?
If the murmur is functional and the rest of the evaluation is reassuring, the plan may simply be monitoring and recheck examinations. That does not mean the murmur was meaningless. It means the veterinarian did enough work to decide it is not currently tied to clinically important structural disease. The owner’s role then becomes observation: breathing rate at rest, appetite, stamina, and any new signs worth reporting between visits (Cornell Feline Health Center, n.d.-a).
If the murmur is linked to HCM, hypertension, hyperthyroidism, or another disease, treatment centers on that diagnosis rather than on silencing the murmur itself. Some cats need medication and long-term monitoring. Others need management of thyroid disease or blood pressure to reduce cardiac strain. The key idea is that the sound is not the target. The underlying condition is (Cornell Feline Health Center, n.d.-b; Cornell Feline Health Center, n.d.-c; Cornell Feline Health Center, n.d.-d).
What quiet follow-up habit makes the biggest difference after today?
One final reason murmurs deserve careful follow-up is that feline heart disease often rewards trend watching more than one-time reassurance. A cat who still feels fine today may only need monitoring, but the value of that plan depends on someone noticing when “normal” begins to drift—faster sleeping breaths, shorter play bursts, new weight loss, or a quieter appetite. In cats, early decline is often visible first in routine habits rather than in dramatic collapse, which is why a murmur should lead to better observation instead of either denial or panic (Cornell Feline Health Center, n.d.-a).
References
- Cornell Feline Health Center. (n.d.-a). Diagnosis: Heart disease. Cornell University College of Veterinary Medicine. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/diagnosis-heart-disease
- Cornell Feline Health Center. (n.d.-b). Hypertrophic cardiomyopathy. Cornell University College of Veterinary Medicine. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/hypertrophic-cardiomyopathy
- Cornell Feline Health Center. (n.d.-c). Hypertension. Cornell University College of Veterinary Medicine. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/hypertension
- Cornell Feline Health Center. (n.d.-d). Hyperthyroidism in cats. Cornell University College of Veterinary Medicine. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/hyperthyroidism-cats