About HCM

Hypertrophic cardiomyopathy (HCM) is a condition characterised by the inward thickening of the heart muscle, resulting in a reduction of chamber volume, thereby reducing the volume of blood that the heart can pump with each contraction. 

Please read more about HCM on our information sheet...

Is HCM genetic?

HCM in humans, in the majority of cases, is an inherited genetic disorder, with over 130 genetic mutations already identified.

It is now also believed that HCM in cats could also be genetic. Recently, genetic mutations have been identified in both the Maine Coon and Ragdoll breeds of cat, and there is ongoing work looking for further mutations in the Norwegian Forrest Cat and Sphinx.  Within the Maine Coon breed, approximately one third of tested cats are positive for the mutation.  However, not all Maine Coons with HCM are positive and this particular mutation has not been identified in any cats other that Maine Coons and their progeny.  The mutation identified in the Ragdoll is located within the same gene as the Maine Coon mutation.  However, this mutation is different to that identified in Maine Coons and to date, there is no information on the incidence of this mutation within the Ragdoll breed.

Genetic testing of affected cats can be useful in identifying which cats carry the mutation.  Whilst a positive test result means that the cat is genetically predisposed to HCM, unfortunately a negative test only means that the cat does not have that one particular mutation.  It does not mean that the cat being tested doesn’t have HCM. 

Is there a screening scheme available to detect cardiomyopathy in cats?

The Feline Advisory Bureau, together with the Veterinary Cardiovascular Society (VCS) have set up a scheme to detect the presence or absence of hypertrophic cardiomyopathy(HCM). See below..

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FAB VCS HCM Screening Scheme

Aims

• To identify cats free from hypertrophic cardiomyopathy (HCM) in specific breeds of cat.

• To collate data for investigation of a possible genetic basis to HCM in a given breed by a breed club nominated person, geneticist or veterinary surgeon.

• To advise the owner, breeder and cat's veterinary surgeon when an abnormality has been identified and recommendations about any further investigation, if indicated.

Methods of heart testing

• Auscultation: examination with a stethoscope

This is an essential part of examining the animals' heart and circulation. Any heart murmurs are identified, timed, localised and graded (grade 0 – 6). Careful note of the heart rhythm is made. Abnormal heart rhythms may occur without murmurs in HCM.

It may be difficult for the veterinary surgeon to detect a quiet murmur in a noisy room or in a cat which fidgets or purrs. Some murmurs may increase or alter at different heart rates, or due to stress or excitement. If a significant murmur is detected, the veterinary surgeon may advise that the condition should be investigated further. Auscultation does not provide a conclusive diagnosis; further investigations are required. Although all veterinary surgeons will check your cat's heart, the FAB VCS HCM scheme will use a veterinary cardiologist, who has received training and has passed post-graduate examinations.

• Electrocardiogram (ECG)

This is always indicated if an abnormal heart rhythm is detected.

• Echocardiogram (with Doppler)

Two-dimensional echocardiography (ultrasound examination of the heart) allows visualisation of a “slice” through the heart in real-time. M-mode and Doppler (spectral, with or without colour flow mapping) echocardiography allows measurements to be taken and compared with normal values. HCM is usually evident using these techniques. In some cases, it is difficult to be certain whether a cat has mild disease. Veterinary cardiologists normally carry out Doppler examinations as this is a very skilled technique which requires considerable expertise and experience.

Further information

If you have questions about HCM the cardiologist testing your cat will be willing to discuss the results of the tests with you, which are summarised on the certificate of heart testing.

Limitations of heart testing

Echocardiography is not a perfect tool for the diagnosis of HCM; however it is the most sensitive method currently available for detecting early signs of disease. Auscultation (listening with a stethoscope for abnormal heart sounds such as heart murmurs) is a less accurate means of detecting affected cats as a significant percentage of cats with HCM will not have an audible heart murmur.

HCM can occur at any age and therefore a single normal echocardiogram does not guarantee that the cat will remain free of the disease. Cardiologists recommend that breeding cats should have an annual echocardiogram during their breeding years. Examining retired cats periodically is also advantageous as this may allow the identification of affected cats that have offspring in a breeding program.

How to arrange to have your cat assessed

In order to fully assess cats for the breeding scheme, a specialised ultrasound machine is required and a veterinary cardiologist qualified to perform spectral Doppler ultrasonography must perform the examination. Ultrasound is a non-invasive procedure. However, ultrasound waves need good contact with the skin, so in order to perform a cardiac scan, it is usual to clip a small section of hair on both sides of the chest, just behind the elbows. Some cats may require a sedative for the ultrasound to be performed. It is advised that cats are not scanned during pregnancy, as this may alter the cardiac function and produce misleading results. In addition, all cats registering for the scheme must be microchipped, this can be done prior to scanning, or (at most centres) at the time that the cat is scanned.

Many of the cardiologists participating in the scheme have agreed to discount the cost of the examination. However, the exact fee charged is at the discretion of the individual ultrasonographer, therefore it is best to ask the cost when booking an appointment. A list of veterinary cardiologists participating in the scheme is provided below.

In order to book an appointment it is necessary to have permission from you normal veterinary surgeon, and they will need to write a letter requesting referral to one of the veterinary cardiologists participating in the scheme.