Hypertrophic cardiomyopathy in cats
Also known as HCM, Feline HCM.
Thickening of the heart wall and the most common heart disease in cats. It can go years without showing any signs and then appear suddenly with fluid on the lungs or a blood clot.
Fast breathing at rest, open-mouth breathing or back legs that do not respond: emergency.
- System
- Heart and circulation
- Is it urgent?
- Not usually
- Spreads to other cats
- No
- Spreads to people
- No
- Origin
- Inherited
- Typical cost in Spain
- Echocardiogram, €120–250; medication, €10–80 a month; emergency care for fluid on the lungs, €500–1,500.
Symptoms
- No signs for a long time
- Fast breathing at rest (more than 30 breaths a minute while asleep)
- Open-mouth breathing
- Tires easily or hides
- Sudden paralysis of the back legs from a blood clot
Causes
Genetic in many breeds (known mutations in the Maine Coon and Ragdoll), and also seen in non-pedigree cats. Hyperthyroidism and high blood pressure can cause similar thickening.
How it is diagnosed
Echocardiography by a cardiologist. NT-proBNP helps, as does the genetic test in Maine Coons and Ragdolls.
Treatment
It cannot be reversed. Anti-clotting drugs are used and, if there is heart failure, diuretics and other medicines prescribed by the cardiologist.
No doses, on purpose: any medicine must be prescribed by your vet for your cat.
Prognosis
Highly variable: many cats with mild forms live normally; with heart failure or blood clots, the outlook is guarded.
Prevention
Regular echocardiograms in breeding cats and in cats of predisposed breeds. Count resting breaths at home.
Breeds at higher risk
It is described more often in these breeds. That does not mean all of their cats will have it, nor that a moggy is free of it.
Frequently asked questions
What causes hypertrophic cardiomyopathy?
Genetic in many breeds (known mutations in the Maine Coon and Ragdoll), and also seen in non-pedigree cats. Hyperthyroidism and high blood pressure can cause similar thickening.
Can hypertrophic cardiomyopathy be cured?
Highly variable: many cats with mild forms live normally; with heart failure or blood clots, the outlook is guarded. It cannot be reversed. Anti-clotting drugs are used and, if there is heart failure, diuretics and other medicines prescribed by the cardiologist.
How much does it cost to treat hypertrophic cardiomyopathy?
As a guide for Spain in 2026: Echocardiogram, €120–250; medication, €10–80 a month; emergency care for fluid on the lungs, €500–1,500. Prices vary a lot between clinics and cities, and out-of-hours emergencies cost more.
Which breeds are most at risk?
It is described more often in Maine Coon, Ragdoll, British Shorthair, Sphynx, Bengal, Persian and Norwegian Forest Cat. That does not mean every cat of those breeds will have it, nor that a moggy is free of it.
More in heart and circulation
Educational content from Michipedia. It does not replace diagnosis or treatment by a vet: if you have any doubt about your cat's health, ask. Costs are a guide for Spain in 2026.