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Feline Hypertrophic Cardiomyopathy (HCM)

Feline Hypertrophic Cardiomyopathy (HCM)

Feline hypertrophic cardiomyopathy (HCM) is the common heart condition diagnosed in cats. In many cats the cause is not known, but in the Maine Coon and Ragdoll breeds genetic mutations are responsible for the development of the disease. It is thought that genetics likely plays a part for most cats with HCM. 

HCM causes the muscular chamber walls of the heart to become thicker (or hypertrophy). The heart cannot fill with blood properly, so it cannot pump blood as efficiently. The heart beats faster and this uses up more oxygen as well as the heart itself losing oxygen. This causes cells in the heart to die off. This worsens the heart's ability to pump blood and can cause arrythmias. Abnormal blood flow through the valves in the heart or “turbulence” makes the sound commonly referred to as a heart murmur. Cats with HCM can suffer from congestive heart failure, blood flow stasis (or slow blood flow) causing thrombi or blood clots to form or may die suddenly from cardiac arrest. 


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Who is affected? 

All cat breeds can be affected by feline HCM, although as noted previously, Maine Coon and Ragdoll breeds have a known genetic predisposition to the condition. In these cats, it may be diagnosed in cats under one year of age, however according to PetSure claims data, it is most diagnosed in cats between 2 and 6 years of age. 

Table: Breed prevalence of Feline Hypertrophic Cardiomyopathy in insured cats, according to PetSure data in the 2020 calendar year: 







Exotic Shorthair


British Shorthair






Domestic Shorthair


Maine Coon






*Prevalence = Total number of unique claiming pets / total number of insured pets across 12-month period. Excludes breeds with less than 500 active pet insurance policies.

Signs of hypertrophic cardiomyopathy (HCM)

Often cats with hypertrophic cardiomyopathy don’t show any obvious signs that they have the heart disease. Some cats might be noted as having a heart murmur or an irregular heartbeat (arrythmia). In cases where the feline patient is suffering from heart failure, they may be showing signs of rapid breathing, panting, difficulty breathing or sometimes coughing. Paralysis and severe pain may be the first signs a cat has a thromboembolism (or blood clot) blocking blood flow, often to the rear legs. In some unfortunate cases, the cat passes away suddenly. 

Diagnosing Feline hypertrophic cardiomyopathy   

Diagnosing HCM often involves ruling out other causes for the patients’ symptoms. X-rays of the heart are often an important way to view enlargement to the chambers in the heart and check the lungs for fluid or pulmonary oedema. Ultrasound of the heart (echocardiography) and ECG (electrocardiography) are also important tools in understanding how the heart is functioning. Blood tests are also commonly performed.  

Managing Feline hypertrophic cardiomyopathy

Management of HCM is largely focussed around managing the secondary effects of the disease such as congestive heart failure. Medications for heart failure can include diuretics to help remove fluid from the lungs. Other medication may also be prescribed, such as pimobendane or enalapril which may help alter the strength of the heart contractions.  In patients at risk of developing blood clots, medication may be recommended to help prevent those clots such as Clopidogrel or enoxaparin (a low molecular weight heparin). Where a feline patient has a thromboembolism (blood clot blocking a blood vessel), there are limited options for treatment. In some cases, pain management and supportive care may be given for long enough that the thromboemboli breaks down or nearby circulation is able to start providing blood to the damaged areas. Unfortunately, this doesn’t occur in every patient so sometimes euthanasia is the recommended course of action.

How much does it cost to treat?

According to PetSure claims data from 2020 (calendar year), the average, single treatment cost relating to HCM in cats was $434 with the highest, single claim being $4,378. The overall treatment cost of managing HCM will vary depending on the treatments that have been recommended and your pets response to those treatments.

Disclaimer: Reimbursement for these claims would be subject to limits, such as annual benefit limits or sub-limits, benefit percentage, applicable waiting periods and any applicable excess. Cover is subject to the policy terms and conditions. You should consider the relevant Product Disclosure Statement or policy wording available from the relevant provider.


  1. Lake-Bakaar, G, 2017, Vincyclopedia of Diseases, Cardiomyopathy, Hypertrophic, Accessed on 11/05/2021
  2. Nelson, R & Couto, 2003, Small animal internal medicine, 3rd edition, Mosby, USA.

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Kylie Mitchell is a veterinarian with over 17 years experience in animal health and welfare, including in the veterinary and pet insurance industries

She has three rescue cats (Noah, Bei Bei and Meeka), four very old cockatiels and a pond-full of fish.

Kylie's pets

Bei Bei
Bei Bei