Understanding HCM starts with the right veterinary conversation.
This page is educational only. Diagnosis, treatment decisions, and medication use must be guided by a licensed veterinarian. Use this section to prepare for an informed conversation about your cat.
What is feline HCM?
HCM, or hypertrophic cardiomyopathy, is a heart muscle disease where parts of the heart wall become thicker than normal. Some cats show no outward signs in the early stages — this is called subclinical HCM, and it is the stage Sirofel™ is intended for. Other conditions — such as high blood pressure or thyroid disease — can also cause heart wall thickening, and your veterinarian will help distinguish between them.
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HCM can be silent in its early stages
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A heart murmur may or may not be present
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Echocardiography (a heart ultrasound) is the main diagnostic tool
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Regular check-ups support earlier recognition
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Follow-up visits help track changes over time
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Some signs require emergency care — see the Treatment Journey page
Why early detection matters.
About Sirofel™.
Sirofel™ is a sirolimus delayed-release tablet brand for veterinarian-directed care of cats with subclinical HCM. It is not a supplement. It cannot be bought directly. Sirofel™ is administered as a weekly tablet, swallowed whole.
If your veterinarian recommends Sirofel™, the decision will be based on a clear diagnosis, baseline bloodwork, and a monitoring plan. The Treatment Journey page explains what to expect step by step.
When Sirofel™ is not the right option.
Sirofel™ is intended for otherwise healthy cats with subclinical HCM. Your veterinarian will not recommend it — or will choose a different approach — if your cat has one of the following:
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Diabetes mellitus — diabetes affects how the body manages sugar; sirolimus may not be suitable
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Liver disease — sirolimus is processed by the liver and may raise liver enzymes
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High blood pressure (hypertension) — needs to be addressed separately
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Heart failure, past or present — different management is needed
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A history of blood clots (arterial thromboembolism)
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Severe outflow tract obstruction or arrhythmias requiring specific therapy
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Known sensitivity to sirolimus
This is why baseline bloodwork and a full veterinary examination come first.
Questions to ask your veterinarian.
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Does my cat need an echocardiogram?
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Does my cat havesubclinicalHCM, or a more advanced stage?
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Could another condition (blood pressure, thyroid) be causing thickening?
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Has my cat been screened for diabetes and liver disease?
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Is Sirofel™ appropriate for my cat — and if not, what is?
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How often will we recheck bloodwork and imaging?
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What side effects should I watch for at home?
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What signs require emergency care?
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How do I give the tablet safely each week?
Contact with an expert
You can message us right now to get more information about the treatment