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Veterinary cardiologist examining a cat with heart murmur using echocardiogram

Heart Murmur in Cats: symptoms, causes and costs

  1. Facts & Vet costs
  2. The Real Cost
  3. Insurance Traps
  4. Common Questions
By Marcel Janik · Last updated Oct 3, 2026

Up to 15% of apparently healthy cats have a heart murmur - but not all lead to serious disease. Most are caused by hypertrophic cardiomyopathy (HCM). An echocardiogram ($400-$800) determines whether a murmur indicates structural disease or is harmless.

What Causes a Heart Murmur
A heart murmur is an abnormal sound caused by turbulent blood flow. The most common cause is hypertrophic cardiomyopathy (HCM) - abnormal thickening of the heart muscle. Physiological (innocent) murmurs in young kittens carry no clinical significance. Other causes: hyperthyroidism, anemia, hypertension. Murmur grade (I-VI) does not always predict disease severity.

Symptoms

Often None Initially
Many cats show no symptoms for years. As the disease progresses, you may see labored breathing, open-mouth breathing (emergency), reduced exercise, sudden hind limb paralysis (aortic thromboembolism), weight loss, lethargy. Sudden death can be the first sign in severe HCM. Cats hide illness well.

Diagnosis

$400-$900
Echocardiogram (heart ultrasound): $400-$800 - gold standard for structure and function. Chest X-rays: $150-$300. Blood panel: $100-$200 for thyroid and other conditions. NT-proBNP test ($50-$100) flags significant disease. Ideally, a cardiologist performs the echocardiogram.

Treatment

$0-$200/Month
Innocent murmurs: no treatment. Mild HCM: monitoring every 6-12 months. Moderate-severe: atenolol or diltiazem ($15-$40/month); clopidogrel ($15-$30/month) to prevent clots. Heart failure: furosemide diuretic ($10-$20/month). Aortic thromboembolism emergency: $1,500-$3,000 hospitalization.

Total Cost

Variable
Innocent murmur: just monitoring. HCM management: $600-$1,200/year for medications and rechecks. Congestive heart failure or ATE: $2,000-$5,000+ acute costs.

Breed Risk

Maine Coon, Ragdoll
Maine Coons, Ragdolls, and British Shorthairs have highest HCM prevalence. Genetic testing available for Maine Coons and Ragdolls (MYBPC3 mutation).

Prognosis

Highly Variable
Innocent murmurs: the outlook is excellent. Mild HCM with no symptoms: years of normal life. HCM with congestive heart failure: median survival 9-18 months. Aortic thromboembolism: guarded, 50% survive the acute episode.

Monitoring & Prevention
Breed-specific genetic tests for HCM mutations (Maine Coon, Ragdoll). Annual cardiac screening for at-risk breeds. Echocardiograms every 1-2 years for diagnosed HCM. Early detection before symptoms appear.

The Real Cost

$600typical annual cost

Echo + annual monitoring for mild-moderate HCM.

Echocardiogram $400-$800
Annual medications $200-$600
Emergency (CHF/ATE) $2,000-$5,000
Red flags

Insurance Traps

Heart murmurs and HCM are common reasons pet insurance claims are disputed.

Coverage Basics

Exclusion
HCM is covered by most policies if enrolled before cardiac findings. Coverage includes echocardiograms, medications, X-rays, and emergency care. Cardiac emergencies can cost $3,000-$5,000.

The Murmur Pre-Existing Trap

Pre-existing
Murmurs detected before enrollment - even soft or innocent ones - may exclude entire cardiac coverage. Insurers deny claims as pre-existing using routine records. Enroll before any murmur is documented.

Breed-Specific Exclusions

Breed
Some insurers exclude heritable conditions in high-risk breeds. Maine Coons and Ragdolls may face HCM exclusions or require negative genetic test proof. Some policies exclude conditions breeds are 'predisposed to' - HCM qualifies.

Cardiac Waiting Period

Waiting period
Some insurers apply longer waiting periods (30-180 days) for cardiac conditions. Heart failure claims shortly after enrollment may be denied due to extended waiting period. Check cardiac-specific waiting periods, not just the 14-day illness period.

Common Questions

Real answers about heart murmur diagnosis, HCM, and insurance coverage.

What causes heart murmurs in cats?
The most common cause is hypertrophic cardiomyopathy (HCM), a thickening of the heart muscle. Physiological (innocent) murmurs occur in young kittens and healthy cats from turbulent flow. Other causes: hyperthyroidism, anemia, high blood pressure, congenital defects. Echocardiogram distinguishes HCM from innocent murmurs.
How serious is a heart murmur in cats?
It depends on the cause. Innocent murmurs require only monitoring. HCM ranges mild (years of normal life) to severe (heart failure, blood clots). Murmur grade (I-VI) doesn't predict severity reliably. Grade II can indicate significant disease; grade V may be less important. Only echocardiography assesses severity.
Do cats with heart murmurs need treatment?
Not always. Innocent murmurs need no treatment, only monitoring. Mild HCM needs echocardiograms every 6-12 months. Medication starts when HCM progresses or symptoms develop: atenolol or diltiazem (slow heart rate), clopidogrel (prevent clots). Heart failure needs furosemide diuretic.
How much does it cost to evaluate a heart murmur in a cat?
Echocardiogram: $400-$800. Chest X-rays: $150-$300. Blood work with thyroid: $100-$200. NT-proBNP test: $50-$100. Total workup at specialty center: $600-$1,200.
What is aortic thromboembolism (ATE) in cats?
ATE ('saddle thrombus') is a blood clot at the aortic bifurcation that cuts off blood supply to the hind legs. It comes on suddenly: your cat can't use its hind legs, is in extreme pain, and the legs feel cold. Survival ~50% with aggressive treatment. Clopidogrel reduces clot risk in advanced HCM.
Which cat breeds are most prone to heart murmurs and HCM?
Maine Coons and Ragdolls have highest HCM prevalence from MYBPC3 genetic mutations. British Shorthairs, Persians, Sphynx, Norwegian Forest, Scottish Folds also at risk. Genetic testing available for Maine Coons (A31P) and Ragdolls (R820W) to identify carriers.
How is HCM different from other heart diseases in cats?
HCM: heart muscle thickens abnormally, reducing chamber volume and filling. Dilated cardiomyopathy (DCM): heart weakens and dilates, historically from taurine deficiency, now rare. Other forms: restrictive cardiomyopathy (RCM) and unclassified cardiomyopathy.
Does pet insurance cover heart murmurs in cats?
Most policies cover HCM if you enroll before cardiac signs are documented. Key trap: murmurs noted at routine exams before enrollment exclude all cardiac coverage as pre-existing. Some policies extend waiting periods (30-180 days) for cardiac. Enroll before any heart murmur is documented.

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Sources

Research and data used to compile this profile.

  1. 1 Paige CF, Abbott JA, Elvinger F, Pyle RL. Prevalence of cardiomyopathy in apparently healthy cats. J Am Vet Med Assoc. 2009;234(11):1398-403.
  2. 2 Fox PR, Keene BW, Lamb K, Schober K, Chetboul V, Fuentes VL, Boswood A. International collaborative study to assess cardiovascular risk and evaluate long-term health in cats with preclinical hypertrophic cardiomyopathy and apparently healthy cats: The REVEAL Study. J Vet Intern Med. 2018;32(3):930-943.