Understanding HCM starts with the right veterinary conversation.

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.

Why early detection matters.

• HCM can be silent in its early stages

• A heart murmur may or may not be present

• Echocardiography (a heart ultrasound) is the main diagnostic tool

• Regular check-ups support earlier recognition

• Follow-up visits help track changes over time

• Some signs require emergency care — see the Treatment Journey page

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:

• Diabetes mellitus — diabetes affects how the body manages sugar; sirolimus may not be suitable

• Liver disease — sirolimus is processed by the liver and may raise liver enzymes

• High blood pressure (hypertension) — needs to be addressed separately

• Heart failure, past or present — different management is needed

• A history of blood clots (arterial thromboembolism)

• Severe outflow tract obstruction or arrhythmias requiring specific therapy

• Known sensitivity to sirolimus

This is why baseline bloodwork and a full veterinary examination come first.