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 Forest 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.  Work at Bristol Vet School on tests on 600 Ragdolls has found 30% positive.

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. For more information on the gene test see below.

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..

HCM Negative register

Cats which have been screened negative, by ultrasound, in accordance with the Feline Advisory Bureau and Veterinary Cardiovascular Society (VCS) Screening Scheme and those tested negative by the gene test (bearing in mind this is only a test for one particular mutation - there may be more) can be listed on the FAB HCM Negative Register.  Click here to view the register...

HCM Gene Test for Maine Coon and Ragdoll

The Molecular Diagnostic Unit at Bristol is now offering genetic testing for hypertrophic cardiomyopathy in Maine Coon and Ragdoll cats.  Hypertrophic cardiomyopathy (HCM) is the most common form of heart disease found in domestic cats, which affected animals at risk of developing congestive heart failure and sudden death.  Feline HCM appears to be more common in some breeds, including Maine Coons and Ragdolls, with a prevalence of 34% in the UK Maine Coon population.  The laboratory at Bristol has tested nearly 600 Ragdolls and found a prevalence of around 30%.

In some HCM affected cats a single genetic defect has been identified in heart muscle.  Maine Coon and Ragdoll breeds have different defects in the same gene (MYBPC3).  Since the cat genome contains two copies of this gene there are three possible genotypes:

• Homozygous wild-type (two copies of the normal gene, i.e.no defective gene).  This means the cat is negative for this particular form of HCM.
• Heterozygous (one copy of the normal gene and one copy of the defective gene).  This means the cat may develop this form of HCM.
• Homozygous mutant (two copies of the defective gene).  There is some evidence that these cats are more likely to develop moderate to severe disease earlier in life when compared to heterozygous cats.

The assay requires either 0.5ml of EDTA anticoagulated blood or a buccal swab sample.  Instructions on how to obtain a diagnostic sample using a buccal mucosal swab can be found here http://www.langfordvets.co.uk/lab_pkdsampling.htm

Please note

A negative result on either the Maine Coon or Ragdoll HCM genetic test means that the cat does not have this specific genetic mutation.  However, cats may still go on to develop HCM due to other mutations, as yet unidentified, but for which there is already considerable evidence of existence.  In addition, cats may also develop other forms of heart disease for other reasons, for example, associated with high blood pressure.

A positive result on either the Maine Coon or Ragdoll HCM genetic test means that the cat carries either one (heterozygous) or two (homozygous) defective copies of the MYBPC3 gene and is likely to develop cardiac disease.  All results will specify whether a genotype is heterozygous or homozygous.

For more information go to http://www.langfordvets.co.uk/lab_pcrnews.htm

*** For inclusion on the FAB HCM Negative Register the cat's microchip number must

be confirmed by a veterinary surgeon at the time of sampling ***

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FAB VCS HCM Screening Scheme (Ultrasound)

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 micro chipped, 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.