Serious severity

Restrictive Cardiomyopathy (RCM)

A serious heart-muscle disease in which stiff, scarred tissue stops the heart's chambers from relaxing and filling properly between beats.

⚠️ Common symptoms

Faster or laboured breathing, especially at restLethargy and reduced appetiteOpen-mouth breathing when stressedSudden hind-limb weakness or pain (from a clot)Collapse or fainting in advanced cases

Restrictive cardiomyopathy is one of the main forms of heart-muscle disease in cats, alongside the better-known hypertrophic cardiomyopathy. In RCM the problem is not that the walls thicken, but that the muscle or its inner lining becomes stiff and scarred. A healthy heart relaxes fully between beats so its chambers can fill with blood; a restrictive heart cannot relax properly, so filling is limited and pressure backs up.

That back-pressure is what makes cats unwell. Fluid can accumulate in or around the lungs, causing the laboured, rapid breathing that owners often notice first. Because the enlarged upper chambers allow blood to pool and clot, RCM also carries a serious risk of a clot lodging where the main artery divides to the back legs, causing sudden, painful hind-limb paralysis known as a saddle thrombus.

Diagnosis relies on an ultrasound scan of the heart, sometimes with X-rays and blood tests. While RCM cannot be reversed, many cats live comfortably for a good while with medication that manages fluid, supports the heart and lowers clot risk, especially when the disease is caught early.

🔍 Causes

The exact cause is often unknown. It is characterised by fibrosis (scarring) within the heart muscle or its lining, which makes the walls rigid. It is one of the more common cardiomyopathies in older cats after HCM.

🛡 Prevention

There is no proven way to prevent RCM, but early detection makes a real difference. Routine veterinary check-ups that include listening for murmurs or gallop rhythms, and heart scans for at-risk or older cats, allow treatment to start before a crisis.

💊 Treatment

There is no cure, so treatment aims to control the consequences of the disease. Vets typically prescribe diuretics to clear fluid from the lungs or chest, medication to support heart function, and clot-preventing drugs to reduce the risk of a dangerous blood clot. Regular scans and monitoring help adjust the plan over time.

When to see a vet: Seek prompt veterinary care for any increased breathing effort, open-mouth breathing, or sudden hind-leg weakness — these are emergencies. Any lethargy or appetite loss in an older cat also warrants a check.

⚕️ Medical disclaimer

  • This information is educational only and is not a substitute for veterinary advice.
  • Symptoms overlap between conditions — only a vet can diagnose accurately.
  • Never withhold treatment or self-medicate based on information found online.
  • When in doubt, call your vet. Early intervention almost always leads to better outcomes.

← Back to Health & Ailments