HCM in Maine Coon Cats
By Dr. Kevin Toman, DVM · Medically reviewed November 1, 2026 · 40+ years in clinical practice · 300+ cats with HCM treated
Short answer: Maine Coons have a known gene change (called MYBPC3-A31P) that raises their risk of HCM, a disease that thickens the heart wall. A DNA test can find it. But a negative test does not mean your cat is safe. Only a heart ultrasound shows whether HCM is actually there.
Why Maine Coons are at higher risk
HCM (hypertrophic cardiomyopathy) makes the heart's main pumping wall grow too thick. Any cat can get it. But in Maine Coons, scientists found a gene change that makes it more likely.
The gene, MYBPC3, makes a protein that helps heart muscle squeeze and relax properly. A small error in that gene can lead to HCM over time.
Not all Maine Coons with this gene variant will get the disease, and some cats WITHOUT the variant will still get HCM.
Confused? Just start by asking your vet for a pro-BNP blood test. It measures your cat's heart muscle stress, and is a good screening tool for any cat.
How the gene works
Every cat gets two copies of each gene, one from each parent.
| Gene result | What it means | Risk |
|---|---|---|
| Negative (N/N) | No copies of this mutation | Lower risk, but HCM is still possible |
| One copy (N/HCM) | Carrier | Higher risk. Many never get severe disease. |
| Two copies (HCM/HCM) | Got it from both parents | Highest risk, often earlier and more severe |
Having the gene raises the risk. It does not guarantee disease. Proven
A negative gene test is not a clean bill of health
This is the most important point in this article.
The DNA test checks for one known mutation. Other genes, and causes we don't yet understand, can also lead to HCM. Many Maine Coons with HCM test negative.
Gene test = risk. Heart ultrasound = diagnosis. You need both.
From Dr. Kevin's 400+ cats with HCM:
Because not all cats with the gene variant get HCM, I recommend simple annual cardiac screening blood testing. It's called pro-BNP, and takes just a couple drops of blood.
Do this test once a year. It's cheap, and may give us the early warning we need for your cat's best outcome.
Symptoms to watch for
Many Maine Coons with early HCM show no signs at all. When signs appear, they may include:
- A heart murmur or "gallop" sound your vet hears
- Less play or energy
- Faster breathing while asleep
- Breathing that looks like hard work
- Eating less
- Fainting or collapse
Many cats with HCM have no murmur. A normal stethoscope check does not rule it out.
Go to an emergency vet now for open-mouth breathing, struggling to breathe, collapse, or sudden back-leg weakness or pain.
How HCM is diagnosed
- Echocardiogram (heart ultrasound): the key test. It measures the heart wall and left atrium. A board-certified cardiologist is ideal for breeding cats.
- Blood pressure and thyroid tests: to rule out other causes of a thick heart.
- NT-proBNP blood test: can flag a heart under strain. It is a screening tool, not a diagnosis.
When should a Maine Coon be screened?
There's no one-size schedule. A common approach:
- Breeding cats: a heart ultrasound before breeding and repeated every year or so.
- Pet cats with the gene, or a family history: start in young adulthood and repeat every 1 to 2 years.
- Any Maine Coon with a murmur, gallop or breathing change: get an ultrasound now.
HCM can show up at any age. One normal scan does not mean your cat is protected for life. Ask your vet to set a schedule.
Buying a Maine Coon kitten? Ask the breeder
- Were both parents gene-tested for MYBPC3-A31P? Can I see the results?
- Did both parents have heart ultrasounds? When, and by whom?
- Has any cat in the family had HCM, heart failure or sudden death?
- Will you share the kitten's gene test result?
If your Maine Coon has HCM
The first step is to find the stage (A, B1, B2, C or D). The stage guides treatment and how often to recheck. Learn about Stage B2 →
Treatment options may include:
- Clopidogrel to lower clot risk in higher-risk cats
- Felycin-CA1, a weekly sirolimus tablet. It was FDA conditionally approved in 2025 for cats with HCM and no symptoms. It targets the thickening itself. Buy Felycin here.
- Heart failure drugs if fluid builds up
Outside the US?
We ship Felycin routinely to the US, UK, and Canada. You start by sending your vet's prescription, or by enrolling your cat in our Cat Longevity Protocol. You can purchase Felycin from us and get guaranteed delivery, although it sometimes takes a few days.
If you live in the EU, Taiwan, Hong Kong, or China you can purchase Felycin from us. You start by enrolling your cat in our Cat Longevity Protocol. You provide the shipping, and we cannot guarantee delivery but we can absolutely send it your way.
Frequently asked questions
Do all Maine Coons get HCM?
No. But Maine Coons have a known breed-linked gene that raises the risk.
My Maine Coon tested negative. Is it safe?
Not for sure. The test only looks for one mutation. A heart ultrasound is still the best way to check.
Can a Maine Coon get HCM later in life?
Yes. HCM can appear at any age, so repeat screening is wise.
Can a Maine Coon with HCM live a long life?
Yes. Many stay stable for years. The outlook depends on the stage and whether problems develop.
Is genetic testing cheaper than an echocardiogram?
Usually yes, but they answer different questions. One shows risk. The other shows what's in the heart right now.
Your next step.
Have a Maine Coon gene test or echo report and don't know where to go? Enroll in our Cat Longevity Protocol.
Free guide: HCM University · Related: HCM in Ragdoll Cats
References
- Luis Fuentes V, et al. ACVIM consensus statement on cardiomyopathies in cats. J Vet Intern Med. 2020;34(3):1062–1077.
- Meurs KM, et al. A cardiac myosin binding protein C mutation in the Maine Coon cat with familial hypertrophic cardiomyopathy. Hum Mol Genet. 2005;14(23):3587–3593. [VERIFY: add link]
- UC Davis Veterinary Genetics Laboratory. Hypertrophic cardiomyopathy (Maine Coon). [VERIFY: link]
- US FDA. Conditional approval of Felycin-CA1. March 2025.
This article is for education only. It does not replace an exam, diagnosis or treatment plan from your own veterinarian. Prices and regulations change; confirm locally.