CATS · Condition guide
Feline hypertrophic cardiomyopathy: real veterinary cases
Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats, affecting roughly 15% of the general cat population and substantially more in certain breeds — Maine Coons, Ragdolls, British Shorthairs, Sphynx, and Persians are over-represented. The heart muscle thickens (especially the left ventricle), the chamber shrinks, and the heart can't relax properly between beats. Many cats live for years with mild HCM and never show symptoms; others progress to congestive heart failure or, terrifyingly, throw a clot into the aorta (aortic thromboembolism — a "saddle thrombus") that causes sudden, severe hind-limb paralysis.
A heart murmur picked up on a routine exam is the most common first clue — though about a third of cats with HCM have no audible murmur, and many cats with innocent murmurs don't have HCM. Confirming the diagnosis requires echocardiography (cardiac ultrasound). NT-proBNP is a useful screening blood test when echo isn't immediately available. Treatment depends on stage: subclinical disease often needs only monitoring, while symptomatic cats benefit from diuretics, beta-blockers, and anti-platelet drugs like clopidogrel to reduce clot risk.
What vets typically check for
- Thorough auscultation — listen for a murmur, gallop sound, or arrhythmia.
- NT-proBNP blood test as a screening tool (good negative predictive value).
- Echocardiography — the only way to definitively diagnose HCM and grade severity.
- Thoracic radiographs if congestive heart failure is suspected (tachypnoea, dyspnoea).
- Clopidogrel for cats at high risk of aortic thromboembolism; diuretics ± pimobendan when in heart failure.
Not a replacement for veterinary care. Use this to walk into the conversation prepared, not to self-diagnose.
Real cases from the veterinary literature
Peer-reviewed reports our semantic search surfaces for Hypertrophic cardiomyopathy (HCM) in cats. Click into any case for the full abstract — or run a personalised search with your pet's exact details.
- End-stage hypertrophic cardiomyopathy in a cat.
The Canadian veterinary journal = La revue veterinaire canadienne · 2015 · United States
A 14-year-old Persian cat was taken to the vet because its heart condition, called hypertrophic cardiomyopathy (HCM), had gotten worse after a serious heart failure episode. This cat had been diagnosed with HCM nearly 13 years earlier. Tests showed that the heart disease was now at an advanced stage, and the cat was experiencing an irregular heartbeat. The cat was sent home wit
- Asymptomatic Hypertrophic Cardiomyopathy: Diagnosis and Therapy.
The Veterinary clinics of North America. Small animal practice · 2017 · United Kingdom
Hypertrophic cardiomyopathy (HCM) is a heart condition that affects about 15% of cats, and the chances of having it increase as they get older. While many cats with HCM can live normal lifespans, some may experience sudden death or develop serious heart problems. A special ultrasound of the heart, called echocardiography, can help identify high-risk cats by showing if the left
- Feline Hypertrophic Cardiomyopathy: Case Report and Challenges in Clinical Diagnosis
Brazilian Journal of One Health · 2025 · United States
A 17-year-old spayed female Persian cat was brought in because she suddenly couldn't use her back legs. The vet found that her legs were cold and there were unusual heart sounds, but her initial blood tests looked normal. Further tests showed that she had thickening of the heart muscle, which can cause blood clots, and she also had cysts in her liver and kidneys. The cat was tr
- The Feline Cardiomyopathies: 2. Hypertrophic cardiomyopathy
Journal of Feline Medicine and Surgery · 2021 · United States
Hypertrophic cardiomyopathy (HCM) is the most common heart condition seen in cats, affecting about 15% of domestic cats, often without noticeable symptoms. While most cats with HCM can live normal lives, a small number may develop serious issues like heart failure or blood clots. Cats of any age, sex, or breed can be affected, but it's more common in male domestic shorthairs. D
- Clinical signs associated with severe ST segment elevation in three cats with a hypertrophic cardiomyopathy phenotype.
Journal of veterinary cardiology : the official journal of the European Society of Veterinary Cardiology · 2024 · United States
Three cats were presented for unusual collapsing episodes. Echocardiography revealed a hypertrophic cardiomyopathy (HCM) phenotype in each cat. Continuous electrocardiographic monitoring showed that the clinical signs coincided with periods of severe ST-segment elevation in each cat.
Frequently asked questions
- How worried should I be about a heart murmur?
- Many cat heart murmurs are 'physiological' or innocent — they don't reflect serious disease. But because HCM is so common, any murmur warrants follow-up. NT-proBNP is a good screening blood test, and echocardiography is definitive. Ask for an echo if the murmur is loud (grade 3+), if the cat is a breed predisposed to HCM, or if there are any clinical signs.
- What is a saddle thrombus?
- Aortic thromboembolism (ATE) is a clot — usually formed in the enlarged left atrium of an HCM cat — that lodges where the aorta splits at the back of the abdomen. The cat suddenly cannot use one or both hind legs, the legs are cold and painful, and the prognosis is guarded. Some cats survive with intensive care, but recurrence is common. Clopidogrel reduces (does not eliminate) the risk in high-risk cats.
- Can HCM be cured?
- No — but many cats live for years with subclinical HCM. Once heart failure or thromboembolism occurs, prognosis is more guarded. Early identification through screening (especially in predisposed breeds) gives the best chance of catching disease before complications occur.