Hypertrophic Cardiomyopathy
What is it?
Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats. The heart muscle thickens, making the heart stiff and less able to fill. It can be inherited in breeds like Maine Coons and Ragdolls but occurs in any cat.
What signs should I watch for?
Signs to watch for include often no signs early on; rapid or labored breathing, open-mouth breathing; lethargy or hiding; and sudden hind-leg paralysis and pain from a blood clot (EMERGENCY).
How is it diagnosed and treated?
A murmur or abnormal rhythm may be the first clue. An echocardiogram (heart ultrasound) confirms the diagnosis; X-rays, blood pressure, and blood tests help. Treatment depends on stage and may include medications to support the heart, control fluid, and reduce clot risk.
Can it be prevented, and what's the outlook?
- Some cats stay stable for years; others develop heart failure.
- Counting your cat's resting breathing rate at home helps catch problems early.
Reviewed by the Adler Veterinary Hospital veterinary team, October 2026.
Any cat; inherited in Maine Coons and Ragdolls
Who's at risk:
Rapid or labored breathing, lethargy, sudden hind-leg paralysis
Main signs:
Ongoing management with your vet
Urgency:
When to call a vet right away
- Sudden hind-leg paralysis and pain (from a blood clot)
- Rapid or labored breathing, or open-mouth breathing
Not sure whether it can wait? Call us anyway. Our team can help you decide.
Source:
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