What are the signs of hypertrophic cardiomyopathy in cats?

Often none; Fast or laboured breathing; Open-mouth breathing; Sudden back-leg paralysis and pain (blood clot); Lethargy.

When should I contact a veterinarian?

Open-mouth breathing or sudden back-leg weakness in a cat is an emergency.

Heart disease · Updated 2026-09-29

Thickening of the heart muscle — the most common heart disease in cats, often hidden until a crisis.

Urgent veterinary attentionCats

Often inherited (Maine Coons and Ragdolls have known genetic forms); high blood pressure and hyperthyroidism can cause similar changes.

Heart ultrasound, blood tests and chest X-rays.

Medication to reduce clot risk and manage heart failure where present.

Screening of breeding cats; regular checks for at-risk breeds.

Very variable — some cats never develop signs, others develop heart failure.

What are the signs of hypertrophic cardiomyopathy in cats?: Often none; Fast or laboured breathing; Open-mouth breathing; Sudden back-leg paralysis and pain (blood clot); Lethargy.
What causes hypertrophic cardiomyopathy in cats?: Often inherited (Maine Coons and Ragdolls have known genetic forms); high blood pressure and hyperthyroidism can cause similar changes.
How is hypertrophic cardiomyopathy in cats diagnosed?: Heart ultrasound, blood tests and chest X-rays.
How is hypertrophic cardiomyopathy in cats treated?: Medication to reduce clot risk and manage heart failure where present.
Can hypertrophic cardiomyopathy in cats be prevented?: Screening of breeding cats; regular checks for at-risk breeds.
When should I contact a veterinarian?: Open-mouth breathing or sudden back-leg weakness in a cat is an emergency.