Feline Hypertrophic Cardiomyopathy (HCM)

About HCM

HCM is a disease that causes thickening of the heart muscle resulting in poor relaxing and filling ability. As the heart’s pumping chamber (ventricle) becomes progressively thicker, less blood can enter the chamber; thus, less blood is ejected out to the body. The cause of HCM is unknown, although certain breeds of cats appear to be predisposed 

HCM breed screening program

Cardiorespiratory Pet Referrals are pleased to be able to offer a HCM breed screening program. Cats are screened by ultrasound (echocardiography), in accordance with the UK Feline Advisory Bureau and Veterinary Cardiovascular Society (VCS) Screening Scheme

Aims

  • To identify cats free from hypertrophic cardiomyopathy (HCM) in specific breeds of cat.
  • 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, breeding 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 we are happy 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. 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.

To assist and encourage breeders to participate in the scheme we have discounted the cost of the examination.

© CardioRespiratory Pet Referrals Victoria 2012