Hypertrophic Cardiomyopathy (HCM)

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Hypertrophic Cardiomyopathy is a genetic disease which affects cats, dogs, pigs and people. How it is passed on in generations is still not clearly discovered. Since the 1970's it is known that HCM is the common cause for heart failure, thrombus and sudden death in cats. A major study has been done on Maine Coon cats in the USA which indicates that HCM in these cats seems to be inherited by a single dominant gene.

Healthy heart
A healthy heart


HCM heart
A HCM diagnosed heart

HCM is characterized by an abnormal thickness of the heartmuscle, mainly at the height of the left side of the heart. Because of the thickening of the heartmuscle the heart becomes less elastic, through which the heart can fill itself less easy. A second consequence is that there is less space for the blood left in the left ventricle, which causes a smaller amount of blood to be pumped around at each heartbeat than normal. The thick heartmuscle can create turbulence in the blood, or the leaking of some valves. This can then cause a heartmurmur, which can be heard by a vet with a stethoscope.

Cats with HCM can get fluid in or around their lungs which can lead to difficult breathing. Other animals may show no signs at all, but they can suddenly drop dead, mostly because of a sudden very severe rhythm disturbance. Some cats develop blood clots that may cause paralysis of the hind legs.

HCM is not a congenital defect, but a disease that develops very slowly. Cats that have HCM very often show no signs before they are six months old, and it can take several years before you can make a diagnosis of HCM. Therefore you must have a specialist performing an echocardiography report on several occasions.

The Swedish Maine Coon Cat Club has worked out a HCM health programme starting on 1 January 2004. Since June 2010 this health programme is administered by PawPeds. All breeds are welcome to join the programme.


Is there a cure?

Unfortunately HCM can not be cured, but affected cats can be treated with medication. Depending on the symptoms of the animal and the state of the heart, diurectics, beta-receptor antagonists and/or ACE-inhibitors will be used.

How is a HCM test performed?

The cat is examined using an ultrasound machine (echocardiographic test) where you can see if there are any abnormally thickened parts, how the heart beats and how the blood flows.

The examination is painless and is usually tolerated very well by the cats. If the cat feels uneasy, it would be better giving the cat a slight sedation (injection) as it is important that the cat lies still on the examination table.

Sometimes it is necessary to shave the cat a little just on the spot where it is going to be examined. In other cats it works very well just spreading the fur apart without having to shave. In order to get good contact with the catís skin and also a good picture of the examined area jelly is being used. The examination lasts for about 30-40 minutes.

Click here to learn more about how to proceed for HCM-testing your cat.
Click here to read about the recommendations on testing and breeding regarding HCM.

Clubs presently participating in this health programme: