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How to recognize a hereditary disease called hypertrophic cardiomyopathy, i.e. HCM, in cats?

author Lucy Byrne | Health and diet

Earlier, this heart disease was attributed only to certain pure-blood breeds. Nowadays, it can even occur in cross-breeds. Another disease which reminds us of how important regular preventive check-ups at the vet are.

Hypertrophic cardiomyopathy (or HCM) is an acquired heart disease. Besides cats, it can even occur in people, or also less frequently in dogs or pigs. It is revealed by thickening the heart muscle to the detriment of chambers. The muscle grows inwards, atria are getting bigger and chambers are getting smaller. Therefore, they are not able to pump enough oxygenated blood to the body. The lack of oxygen then causes organ damage.

It is not known if the disease is transferred or inherited. However, recent studies found a gene responsible for the emergence or amplification of HCM. The origin of a genetic disease has been already proven in Maine Coon cats and newly also in Ragdoll cats. This disease is most common in British Shorthair, the already-mentioned Maine Coon and Ragdoll but also in Norwegian Forest, Neva Masquerade or German Rex. But the increasing trend of HCM is also in other breeds and it is also spread among common cats..

Young cats between 1 and 5 years of age are at most risk. But even cats older than 10 years can fell ill. But in such case, this is usually secondary hypertrophic cardiomyopathia related to old age.

Even though this is not an inherited disease, with regard to the proven heredity and found single gene responsible for abnormal heart changes, it can be called an inherited genetic disorder. Cats are already born with faulty genetic makeup which starts a slow development of the disease. Cats for breeding of risky breeds should therefore undergo regular cardiological examination.

So how can we say our cat has HCM? Above all, take your cat to regular checkups. They can reveal a heart murmur in a young cat (which occurs in 40–50 % cats with HCM). In such case, the cat has to undergo a detailed heart examination which reveals its cause. There might various symptoms of the disease in different cats. In the advanced stage, hind limbs might get paralyzed, pulmonary oedema and also pleural effusion might occur (fluid between the lungs and the chest wall).

You might notice frequent abdominal breathing with a mouth wide open. Moreover, a cat will try to relieve itself by lying on a rib cage with an outstretched neck a bit opened mouth and massive abdominal breathing. In this stage, it already has a large amount of fluid in its chest. By that time, the cat doesn’t have to have any symptoms or they are so imperceptible that you won’t associate them with HCM. Some of them are gloominess, lethargy, fast and frequent tiredness, occasional coughing you might mistake for nausea, unconsciousness, muscle loss or decreased appetite.

ECG test (if the cat has arythmia), X-ray of the chest to evaluate the size of heart and lungs and mainly a heart test using echocardiogram is necessary to detect the disease. For older cats, also blood pressure should be taken and the hormone level in the thyroid gland should be determined. Due to the lack of symptoms, HCM in cats is very often detected by chance at a preventive checkup or with X-rays done because of other problems, but sometimes even sudden death occurs.

This is a lifelong disease but there are several medical preparations nowadays and properly selecting the right medicine and by thorough examination, they can significantly elongate the cat’s life. But it depends on the stage of the disease and an individual cat’s condition. If you detect HCM in a timely manner, suitable treatment can elongate your cat’s life by 2–4 years. But you can’t skip regular checkups at the vet and cardiologist. Because it is necessary to perform control blood examination and adjust the treatment.