Five cat breeds that suffer from hypertrophic cardiomyopathy (HCM)

I can quickly think of five cat breeds that are predisposed to suffering from HCM. They are: Maine Coon, Bengal, Ragdoll, Scottish Fold, and American Shorthair. The list is not comprehensive. It doesn't need to be comprehensive for me to question whether purebred cats are more predisposed towards HCM than random read cats. And if they are, why? HCM does affect random read cats and is the most common heart disease and is one of the most common diseases amongst domestic cats.

Ragdolls can inherit HCM. Photo: copyright Helmi Flick

You probably know that HCM describes a thickening of the muscles of the heart. The disease is listed as genetically inherited in my books but I also read that the causes are unclear. A study published in the Journal of Veterinary Cardiology titled "The genetic basis of hypertrophic cardiomyopathy in cats and humans", states in the summary that "mutations in genes that encode for muscle sarcomeric proteins have been identified in humans and in breeds of domestic cats with hypertrophic cardiomyopathy.

In people, HCM is a genetic disease. It is a disease of the sarcomere. Sarcomeres are the basic contractile units of muscle and sarcomeric proteins are responsible for the strength, speed and extent of muscle contraction. So, this study is saying that a genetic mutation affects heart muscles, specifically sarcomeres, which causes HCM in both domestic cats and humans.

If it is a genetically inherited disease, I would have thought that no purebred cat would suffer from it because cat breeders could remove carriers of the disease from their breeding lines. That may be an oversimplification. Perhaps the disease is embedded so fundamentally within some cat breeds, going back to foundation cats, that it is impossible to remove this gene from the breeding lines. I just don't know but if that is the case it is surely a failure in the breeding programmes of the purebred cats mentioned in the first paragraph.

Perhaps HCM in these cat breeds and others is the product of selective breeding which is essential to the creation of purebred cats. Cat breeders have to select individual breeding cats that have the correct characteristics in terms of appearance as per the breed standards. Therefore, the breeding stock is reduced in number, which means the cats are inbred. Selective breeding encourages the inheritance of defective genes.

It seems that inherited illnesses such as hypertrophic cardiomyopathy are part of the package when you adopt some purebred cats. They go with the territory. However, I just wonder whether it is possible to change this perception and remove HCM from these popular breeds. I have quite a big page on HCM and Bengal cats which might interest you.

Bengal cats blighted with inherited HCM. Photo: copyright Helmi Flick

The Bengal Cat Club (UK club) so that breeders do their best to eliminate HCM from breeding lines. They say that there is very little information about the prevalence of the disease in the various breeds. In other words, how do breeds compare with each other in terms of a predisposition to getting HCM? Perhaps there needs to be more data on that available through a study? 

They say that there are a number of causes but breeders are obviously more concerned with hereditary HCM. As mentioned above, it is caused by a defect in a gene coding for a particular protein in the cardiac muscle cells that make up the heart wall. When the gene is defective the muscle cells are abnormal and they do not contract properly. The heart produces more muscle cells to compensate for this deficiency which results in a thickening of the heart wall.

The upshot is that the ventricles of the heart cannot relax and fill properly, the mitral valve becomes distorted which results in progressive congestive heart failure, the symptoms of which are lethargy and reduced exercise tolerance and an increased respiratory rate.

They say that there is no DNA test at the time that they wrote their article for HCM and Bengal cats. The article is undated. They say that breeders should buy breeding cats from "echo tested lines". This means cats which have been tested with echocardiograms. 

When mating a female cat with a stud cat they say that breeders should use a stud cat who is ideally four years old plus and who has been scanned negative for the disease. It appears that HCM can develop later in life and therefore if you wait you can then detect whether HCM has developed or not. Also, do not sell cats for breeding from young parents as they may develop HCM later. That is another feature of their advice.

All Bengal cats should be screened with echocardiography annually, ideally. It is a very complicated subject from my reading of it. It is difficult to remove the genetic inheritance of HCM from Bengal cats. This probably applies to other cat breeds; the ones mentioned above for example.

It is a great shame that such a wonderful cat as the Bengal is blighted with such a profoundly serious genetically inherited disease. The same sentiment would apply to the other cats mentioned.

Maine Coon cat: top 5 health conditions claimed for under pet insurance

Tesco Bank Pet Insurance usefully provide the public with the top five health conditions claimed for by owners of the Maine Coon cat in the UK. It is interesting and perhaps revealing. The information may not be generally indicative of Maine Coon health issues. It tells us that the Maine Coon in the UK typically might suffer from these health issues. They appear to point to diseases of internal organs. 

Average Treatment Costs Table

Condition	Average treatment cost
Lump	£439.47
Diabetes	£221.93
Pancreatitis	£425.21
Hyperthyroidism	£229.70
Organ tumour	£949.61

Average annual pet insurance premiums by cat breed - top five

The information in the table relates to the period 01/01/18 to 31/12/18 and refers to paid treatments including excesses. They say that Maine Coons can suffer from specific ailments although they describe the breed as relatively healthy. 

They can suffer from the common heart condition hypertrophic cardiomyopathy which affects middle-aged cats. The heart grows bigger and the symptoms are shortness of breath, reduced appetite and a reduction in activity levels.

They mention tumours. To the best of my knowledge, Maine Coons are not predisposed to developing cancer tumours. But Tesco argues that common feline growths include lipomas (benign fatty tumours), mast cell tumours (a cancer of the immune system) and lymphomas (a cancer of the lymph nodes).

Tesco Pet Insurance do say that this breed may be predisposed to developing inflammatory bowel disease (IBD). The small or large intestines becomes inflamed. My research indicates that it can be quite difficult to cure this disease in felines. I have a page on home remedies for this disease which you can read by clicking on this link.

I have a page on Maine Coon cat health problems - click here to read it. In a post I wrote in 2018 I said that Maine Coons are more expensive to insure than Bengal cats in the UK.

Tesco Bank Pet Insurance helpfully provide us with some suggestions for Maine coon cat names: Max, Luna, Bella, Milly, Lola.

Maine Coon cat. Photo: copyright Helmi Flick and published here with her express permission.

HCM in Maine Coon cats

The prevalence of HCM in Maine Coon cats that were asymptomatic (got the disease but no symptoms) and in Sweden is set out below:

Background

Maine coon cats have a familial disposition for developing hypertrophic cardiomyopathy (HCM) with evidence of an autosomal dominant mode of inheritance [1]. The current method to diagnose HCM is by the use of echocardiography. However, definite reference criteria have not been established. The objective of the study was to determine the prevalence of echocardiographic changes consistent with hypertrophic cardiomyopathy in Swedish Maine coon cats, and to compare echocardiographic measurements with previously published reference values.

Echocardiography is cardiac ultrasound.

Methods

All cats over the age of 8 months owned by breeders living in Stockholm, listed on the website of the Maine Coon breeders in Sweden by February 2001, were invited to participate in the study. Physical examination and M-mode and 2D echocardiographic examinations were performed in all cats.

Results

Examinations of 42 asymptomatic Maine coon cats (10 males and 32 females) were performed. The age of the cats ranged from 0,7 to 9,3 years with a mean of 4,8 ± 2,3 years. Four cats (9,5%) had a diastolic interventricular septal (IVSd) or left ventricular free wall (LVPWd) thickness exceeding 6,0 mm. In 3 of these cats the hypertrophy was segmental. Two cats (4,8%) had systolic anterior motion (SAM) of the mitral valve without concomitant hypertrophy. Five cats (11,9%) had IVSd or LVPWd exceeding 5,0 mm but less than 6,0 mm.

Conclusion

Depending on the reference values used, the prevalence of HCM in this study varied from 9,5% to 26,2%. Our study suggests that the left ventricular wall thickness of a normal cat is 5,0 mm or less, rather than 6,0 mm, previously used by most cardiologists. Appropriate echocardiographic reference values for Maine coon cats, and diagnostic criteria for HCM need to be further investigated.

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HCM in Maine Coon cats (the original title is "Prevalence of myocardial hypertrophy in a population of asymptomatic Swedish Maine coon cats" - This article is reproduced under a Attribution 2.0 Generic license. These are the details appertaining to this article:

(HCM in Maine Coon cats) - Copyright © 2008 Gundler et al; licensee BioMed Central Ltd.

Prevalence of myocardial hypertrophy in a population of asymptomatic Swedish Maine coon cats

Suzanne Gundler,corresponding author1 Anna Tidholm,2 and Jens Häggström3

1Bagarmossen Animal Hospital, Ljusnevägen 17, S-128 48 Bagarmossen, Sweden

2Albano Animal Hospital, Rinkebyvägen 23, S-182 36 Danderyd, Sweden

3Department of Physiology, Faculty of Veterinary Medicine, Swedish University of Agricultural Science, PO box 7018, Uppsala, Sweden



Update

9th July 2011: VG, a work colleague and a professor has added some useful scientific thought to the matter of the limitations of the echocardiography. You can see her comments on the document referred to above annotated to the document.

 These are VG's comments:

• How the cardiogram is done is important. (not for amateurs), say at cat shows (my comment: the person who I saw at a cat show in Oklahoma doing ultrasound was a professional and he used a mobile ultrasound device (see video above).
• Cats’ hearts are affected in different ways and there is no typical pattern of morphological measures/ abnormalities from echocardiograms for cats with HCM. So, it’s not a simple thing, like “look here” “see that” It’s not like getting your car’s muffler checked.
• Seems like the breeders in Stockholm were interested in participating in this study.
• There may be other heart abnormalities that eventuate in HCM, or possibly sudden cardiac death.
• Whatever heart anatomy abnormalities [were] observed via echocardiogram [they] were not due to random other diseases.
• The diagnostic criteria differ according to cardiologists, and how different researchers define “abnormality”. This is important! So, It is not an exact science.
• They are being cautious as to how the percentage range of HCM they report for the cats in their study would extrapolate to the global MC population. This is a responsible statement. It does not, however, take away from the more general thrust of the problems with using echocardiograms to assess HCM.
• [a] more recent article I am analyzing certainly suggests that the one identified genetic mutation for MCs is not the only mutation responsible for HCM. From the Meurs study (or studies), - different mutations in Maine coons and Ragdolls.