Let’s talk about something that’s not easy—but it’s real.
You might have come across three little letters while researching Maine Coon cats. These letters carry a lot of weight: HCM. It stands for Hypertrophic Cardiomyopathy, and it’s one of the most common heart diseases in cats—especially in Maine Coons.
Whether you’re already a Maine Coon parent or thinking about getting one of these gentle giants, this post will guide you. It will help you understand HCM. We want to give you the truth—not to scare you, but to empower you.
What Is HCM?
HCM is a disease of the heart muscle. It causes the walls of the left ventricle (the heart’s main pumping chamber) to thicken over time. This thickening makes it harder for the heart to fill with blood. As a result, the heart can’t work properly.
In the early stages, most cats show zero symptoms. That’s part of what makes HCM so scary. You might not know anything is wrong until your cat collapses—or worse.
Sudden death is often the first sign in cats that weren’t showing any outward signs of illness. It’s heartbreaking and completely blindsides even the most attentive owners.
After extensive research, this video stood out as the most informative. It’s 20 minutes long. If you’re dealing with HCM in your cat, the video is a must-watch. It explains HCM and offers hope for the new treatment. His websites are also valuable resources: HelpingPetsLiveLonger.com and RapamycinforCats.com
How We Work to Reduce the Risk
At Sassy Koonz, we use two primary screening tools to reduce the risk of HCM:
- DNA Testing: MyBPC3 is the name of a specific gene that helps control how the heart muscle functions. In Maine Coons, a mutation in this gene has been linked to the development of HCM. Cats that inherit one or two copies of this mutated gene are at a higher risk of developing the disease. DNA testing will reveal if the cat carries this gene. Only cats with negative results are used in our breeding program.
- Echocardiograms (echos): Ultrasound scans of the heart performed by our board-certified veterinary cardiologists. They see the actual structure and function of the heart. Only cats with normal hearts (no signs of HCM) are used in our program.
You can do a deep dive into all our Maine Coon health testing protocols and real time HCM reports.
It’s important to remember that:
- Not all cats with the MyBPC3 mutation develop HCM.
- Not all cats with HCM have the known MyBPC3 mutation.
- Not all cats with clear echos will live without HCM forever.
- Many cases go undiagnosed unless the cat has a sudden cardiac event.
Still, even with the best practices, we cannot promise that a kitten will never develop HCM. The parents of the kitten can both have clean DNA. They can also have normal echocardiograms. Yet, they may still develop HCM at some point in their life.
A Heartbreaking Reminder That HCM Doesn’t Play Fair
I’ll never forget a very gut wrenching story that unfolded when I first became a breeder. I was following a very popular, highly respected Maine Coon breeder on social media. This breeder was extremely diligent about preventing HCM in her cattery. Every year she loaded up her cats and took them to the cardiologist to have echocardiograms performed. With pride, she posted negative results every year.
Then one day, out of the blue, her gorgeous soul mate male that was working as a stud died suddenly. Bewildered, she had a necropsy done on him to determine the cause. It was HCM. How could this have happened when he’s been showing clear echocardiograms every year?
That was the last day she ever worked as a Maine Coon breeder. Her hopes and aspirations of contributing to the breed died the same day her cat did. She closed her cattery forever, and I’ve never heard from her again.
Unfortunately, HCM is sneaky and can show up suddenly and always, unexpectedly. That was the day I realized we can do all the preventative measures possible. Ultimately, there’s no guarantee that can ever be made that my or your cat will not get HCM.
What Can You Do to Protect Your Maine Coon’s Heart?
Screening via Echocardiograms
It’s recommended that you do echocardiogram screenings every year until the cat is 5 years old. After that, every other year.
Choose quality nutrition
Look for a food that is high in animal-based protein. Ensure it is low in fillers. It should meet AAFCO standards for your cat’s life stage. Protein fuels heart health.
Avoid obesity
Maine Coons grow big, but they shouldn’t be fat. Extra weight puts extra strain on the heart. Stick to portion-controlled feeding and avoid free feeding when possible. If you have an overweight Maine Coon, get some tips on how to help them reach their ideal weight.
Keep them active
Even indoor cats need to move. Use toys, cat wheels, or climbing towers to encourage movement and reduce stress. Play is heart-healthy! Here are some enrichment ideas.
Supplements
While supplements aren’t a cure, there are some that can support heart muscle function and overall cardiovascular health. Always check with your vet before adding anything to your cat’s routine.
Here are a few that are commonly used:
- Taurine – This amino acid is essential for cats and supports heart function. Most high-quality cat foods include taurine, but supplements can help in some cases.
- Coenzyme Q10 (CoQ10) – May help improve heart muscle energy and reduce oxidative stress.
- L-carnitine – Helps transport fatty acids into cells, which can improve heart metabolism.
- Omega-3 fatty acids – Found in fish oil, they help reduce inflammation and may support healthy blood flow.
- Feline Cardiac Support – a supplement designed specifically for cats by Natural Process.
Again, none of these are magic bullets, but they may help slow progression or support overall wellness when used appropriately. Always talk to your vet and get professional advice before giving your cats supplements.
The New Hope: FDA-Approved Medication
In March 2025, the FDA granted conditional approval for Felycin‑CA1. This drug is a once‑weekly, delayed‑release form of sirolimus (rapamycin). It marks the first-ever drug approved specifically to treat subclinical HCM in cats.
I’ve notified my owners of cats with HCM about this groundbreaking development, and want to share it here as well. It’s still an early rollout, and not all vets are prescribing it yet.
Here’s why this is big news for Maine Coon owners and breeders:
- Targets heart thickening early. Felycin‑CA1 is designed for cats in the subclinical phase, where the heart walls are thickening but there are no outward symptoms yet.
- Shown to reverse changes. Early clinical trials have demonstrated that sirolimus can slow or even reverse the thickening of the ventricular wall.
- First-of-its-kind approval. This isn’t just a step forward—it’s a leap. It’s the first FDA-approved treatment for feline HCM of any kind.
- Veterinarians expect the drug to be prescribable by summer or August 2025
What Owners Should Know
- It’s not for all cats. It is only for cats with subclinical HCM (Stage B). These cats have visible heart thickening with no symptoms.
- Safe, low-dose treatment – Given once weekly at around 0.3 mg per kg, it’s designed not to suppress the immune system at this dose .
- Vet guidance matters – This is not suitable for cats with liver issues or diabetes. Liver health must be checked before starting. Find a vet that’s knowledgeable about HCM and more specifically, Maine Coons.
- Still under study – While early results are promising, researchers are tracking long-term effects. These include survival, quality of life, and progression. This tracking will continue in larger trials through 2028.
Frequently Asked Questions About HCM in Maine Coons
How long can a Maine Coon live with HCM?
Early detection of HCM can extend your cat’s life considerably. If discovered early enough (before the heart thickens), your Maine Coon could qualify to try Felycin‑CA1. This is a promising drug that could reverse HCM. If HCM is discovered later, then the average life expectancy is not set in stone. Some may live for years with no symptoms. While others may have heart failure at 5 years old.
Why do so many Maine Coons have HCM?
There are a few reasons: Genetic predisposition – Maine Coons are one of the breeds with a known mutation (MyBPC3) that can lead to HCM. Also, these cats are big. Their hearts work harder just due to their larger frame. So even though not every Maine Coon will develop HCM, the breed is definitely at higher risk.
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While this is a terrifying subject I really appreciate this valuable information. Thank you for your continued support.