I have had multiple requests from readers asking for more information about HCM in Ragdolls. They want to know what is HCM and also what to do if your kitty has it.
From another breeder friend, I found out that Sue Shorey of SuPurr Ragdolls and also the current RFCI President has done extensive research on HCM in Ragdolls. So I asked her if she would be so kind to write an article for the site.
Her article is below. Thank you, Sue, for helping all the beautiful Ragdolls with this knowledge!
Hypertrophic cardiomyopathy (HCM) is a heart disease where areas of heart muscle enlarge and thicken. It is the most common heart disease in cats both purebred and domestic and has been found to be inherited from the parents.
When the left ventricle becomes thickened, is unable to fill with a normal volume of blood, it follows that less than a normal amount of blood is pumped out to the body with each heartbeat. If the blood supply to other vital organs is inadequate, the heart rate may increase as the body attempts to compensate which can increase the filling pressure on the left side of the heart and contribute to congestive heart failure. Signs could be a heart murmur, weight loss, weakness. A cat could have some, all, or none of these signs.
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The left atrium of the heart enlarges due to the increased pressure which can slow blood flow and cause blood clots to form. Clots dislodge and can become lodged blocking the flow of blood. Rear leg paralysis can be a result of a clot blocking the branches of arteries that go to the rear legs.
Research was started in 2005 for the Ragdoll breed to try and find a HCM DNA test to determine if a cat was carrying the HCM mutation. Our breed was lucky enough that Dr. Kate Meurs did just that! In May of 2007 Dr. Meurs found the MyBPC3R mutation and we now have a DNA test available that anyone can use to be sure that breeders that are being used, or pets that are purchased, are not carrying this one mutation. Several years ago, a DNA test for Maine Coons was also developed which was a different mutation that was found in a very few Ragdolls. While there may be more mutations found in Ragdolls at some future date, none have been found, to date beyond the two mutations. A Ragdoll should be tested for both of these mutations to be sure that they are not carrying either of the two known mutations found in cats.
Most, if not all, HCM cases in Ragdolls are caused by a mutation that is inherited from their parents. A cat can carry one mutation or it can carry two. It can get one from each parent or it can only get one, etc. Usually a cat that has inherited two mutations from each parent (homozygous) will have a severe case of HCM. Those carrying only one mutation (heterozygous) can sometimes have a lesser case but not necessarily!
If you find that your cat has HCM, it is very important to get them an echocardiogram at a certified cardiologist. They will be able to determine if your cat is expressing the disease (heart is actually showing signs of it) or if they appear healthy the moment and show no signs. Ones that are expressing the disease can be put on medications that can help lengthen the lifespan of your kitty. While HCM cannot be cured, there are medications that can really help. Any kitty found to be carrying an HCM mutation, should be checked periodically by a cardiologist. A veterinarian cannot always tell if a cat has HCM or not because it can have a heart murmur or not. A cat with HCM can seem to be acting perfectly normal one day and throw a clot and die the next.
The most important thing for breeders is that they are only breeding with NEGATIVE cats. If the parents are free of any mutations, then the kittens will be too. Ragdoll cats can die young with carrying just one mutation so it is very important to know the health status of your Ragdoll. It is up to the pet buyers to be sure that the breeders are breeding with only negative cats and you should ask for proof that testing has been done by proven labs. The ones I recommend are:
NCSU http://www.cvm.ncsu.edu/vhc/csds/vcgl/index.html (RD & MC testing)
UC Davis http://www.vgl.ucdavis.edu/services/cat/ (RD testing only)