If your cat has ever seemed “a bit off” for a day—sleeping more, playing less, moving slower—you’ve probably wondered whether it’s just age or something more.
With hypertrophic cardiomyopathy (HCM), that uncertainty is exactly the problem. Cats can look normal for a long time, even while their heart is under strain. The good news is that when you know what to watch for, you can act early and make a real difference to your cat’s comfort and safety.
What Is HCM in Cats?
HCM is a thickening of the heart muscle.
As the heart walls thicken, the heart becomes stiffer and does not relax properly between beats. This can reduce how efficiently blood moves through the body and, in more advanced cases, lead to complications such as fluid build-up around the lungs.
Important to know: HCM is often manageable. Many cats live good, happy lives with the right veterinary care and sensible home routines.
Why Does Feline HCM Happen?
In many cats, there is not one clear cause. Vets commonly consider several contributing factors.
- Genetics: Some cats may be predisposed, especially within certain breed lines.
- Age: More commonly diagnosed in middle-aged and older cats, though younger cats can be affected.
- Other conditions: Issues such as high blood pressure or thyroid disease can strain the heart and may need ruling out.
Myth to debunk: “Only pedigree cats get HCM.”
Reality: Any cat can develop it—purebred or moggy.
Early Signs Owners Often Miss
Cats are experts at hiding illness. Early HCM can be completely silent or appear as vague changes that are easy to dismiss.
- Less interest in play, especially sudden or unexplained
- More resting than usual or tiring quickly
- Changes in breathing, such as breathing faster at rest or panting after mild activity
- Reduced appetite or unexplained weight loss
- Increased hiding or withdrawal
A Practical Check You Can Do at Home
When your cat is asleep and relaxed, count their breaths for 15 seconds and multiply by four.
If your cat’s resting breathing rate seems consistently higher than their normal, contact your vet—especially if lethargy or appetite changes are also present.
The Emergency Sign You Should Never Ignore
One of the most serious complications linked to HCM is a blood clot that blocks blood flow, often affecting the back legs.
Emergency warning signs include:
- Sudden collapse or extreme distress
- Crying out in pain
- Inability to use or dragging of the back legs
- Cold paws or sudden weakness
If any of these occur, contact an emergency vet immediately.
How Vets Diagnose HCM
Because symptoms can overlap with other conditions, diagnosis usually involves several checks rather than a single test.
- Physical examination and listening to the heart
- Blood pressure measurement
- Blood tests to assess overall health and rule out other causes
- Chest X-rays to check for fluid build-up
- ECG to assess heart rhythm
- Echocardiogram (heart ultrasound), often the most informative test
Myth to debunk: “No murmur means no heart disease.”
Reality: Some cats with HCM have no murmur at all.
Treatment: What Management Can Look Like
HCM usually cannot be cured, but it can often be managed effectively.
Depending on your cat’s condition, a vet may recommend:
- Medication to support heart function or regulate heart rate
- Medication to reduce fluid build-up if present
- Medication to reduce clot risk in certain cases
- Regular monitoring and follow-up scans
Key point: Management plans are individual. Two cats with HCM may require very different approaches.
How to Support a Cat With HCM at Home
Home care is about consistency and calm, not doing everything at once.
1. Keep Life Predictable
A stable routine helps reduce stress.
- Consistent feeding times
- Quiet resting spaces
- Gentle interaction without overstimulation
2. Make Your Home Easy to Navigate
If your cat is less keen to jump, adjust the environment.
- Add step stools to favourite spots
- Keep food and water easily accessible
- Consider keeping essentials on one level
3. Encourage Hydration Without Pressure
Hydration supports overall wellbeing.
- Water fountains may encourage drinking
- Wet food can help if recommended by your vet
4. Keep the Litter Area Calm and Clean
Cats with health issues can become sensitive about toileting. A clean, quiet setup reduces stress and helps you spot changes early.
- Scoop daily, twice daily in multi-cat homes
- Place trays in quiet, accessible locations
- Use a low-dust, high-absorption litter such as Pacha Litter
A steady litter routine also makes it easier to notice changes in output, which can be helpful when monitoring an ongoing condition.
When to Call the Vet
Contact your vet promptly if you notice:
- Breathing that looks faster or more effortful at rest
- Panting or open-mouth breathing
- A noticeable drop in appetite
- Sudden tiredness or withdrawal
- Collapse, fainting, or sudden mobility changes
Final Thought
HCM can sound frightening, but your response does not need to be.
Calm observation, early action, and good veterinary support go a long way. Your cat will not tell you when they are struggling, but with simple habits and a home that prioritises comfort, you can help them feel safe, steady, and well cared for every day.
