Thread: HCM gene testing- are we wasting our time?

Yes it is a shame that research is always profit driven......I would also be interested in how diet and obesity affects outcome for feline HCM! But that's another story, and another piece of research that wont get done. Although the cat food industry might be interested.....

NCarver- it is indeed encouraging that heterozygous status was not strongly associated with LVH, although as you say, some of the cats weren't massively old. I'm really sorry to hear about your cat which died through HCM- I only hope that Sylvester's murmur does not worsen (my boss suggested I put him on beta blockers early, but he is only drawing from experience with humans.... but then it seems like this is all the information we have).

Hi Catlover,what grade murmur has Sylvie got,my daughters MC had one picked up at a pretty early age,it stayed at grade 1 for several years & has now gone to grade two,she is 11.5ysr old,full of life & in no need of medication yet,I know there are lots of causes of heart murmurs in cats,some cardiac,some non cardiac but at the momen it seems as if it is a MC then it must be HCM related.As a matter of interest{all my cats are pet neuters} I swabbed three of them,all came from different breeders & they all came back as negatives,the eldest one is 13.5yrs & she is the mother of the above cat.
It is going to be very interesting to see over the next few years what the outcome of this is,especially if another gene is isolated....

My ancient moggie Barney has a grade 6 murmour, but no vet has said it needs treatment. How much of a worry should it be anyway?

They can be a very big worry,some causes are really dangerous to the animal,some are dangerous if not treated accordingly,some just carry on with life & no medication,obviously its all down to the cause, but if Barney is happy & enjoying life & your vet hasn't suggested him going on medication then he must be happy that Barney is coping.....

Originally Posted by jckkerrison

Hi Catlover,what grade murmur has Sylvie got,my daughters MC had one picked up at a pretty early age,it stayed at grade 1 for several years & has now gone to grade two,she is 11.5ysr old,full of life & in no need of medication yet,I know there are lots of causes of heart murmurs in cats,some cardiac,some non cardiac but at the momen it seems as if it is a MC then it must be HCM related.As a matter of interest{all my cats are pet neuters} I swabbed three of them,all came from different breeders & they all came back as negatives,the eldest one is 13.5yrs & she is the mother of the above cat.
It is going to be very interesting to see over the next few years what the outcome of this is,especially if another gene is isolated....

The vet didn't say, just commented on it then said 'but then he seems a bit stressed by being here, his heart is going like the clappers'. I assume therefore that it is fairly low grade- having now met the breeder it sounds like he didn't have a murmur when vet checked by her as a kitten. I guess all I can do at the moment is make sure he has a stress-free life. Dudley is a bit of a stressor and has definitely made him more active playing 'chase me chase me', but hopefully having company will be good for him in the long run!

Originally Posted by Catlover

I'm really sorry to hear about your cat which died through HCM- I only hope that Sylvester's murmur does not worsen (my boss suggested I put him on beta blockers early, but he is only drawing from experience with humans.... but then it seems like this is all the information we have).

Though his passing was of course very sad, we did manage to give him almost four years of great and actually quite healthy life. Every time I think about his last few hours, though, it is very hard not to get upset. If we had known that nothing would work and how much he would suffer we would have had him put down immediately, but we and the vets assumed he could be pulled through the incident (which came quite out of the blue, with no warning signs). Some cats with HCM just pass suddenly and with little/no pain. Others, though, go into CHF or throw clots and suffer greatly at the end.

At various points and in various combinations, Karma was on diuretic, beta-blocker, and calcium channel blocker. We eventually reduced him to just the calcium channel blocker, as that was what seemed to make him feel best. Beta-blocker definitely reduced his energy levels. As far as I know, though, best practice for vet cardiologists in US is still not to do any treatment at all on unsymptomatic cats as they do not believe any treatments slow progression or prolong life. We are still planning on having our hetero girl Allie echoed at least every two years so that we know the condition of her heart and thus might have better warning about any symptoms that develop. In a sense, though, it is pointless as nothing would be done based just on the echo results.

As already stated, some murmurs could be quite benign and some could indicate a serious problem. The only way to know for certain is to have an echocardiogram done by what in the US is called a "board certified veterinary cardiologist." Not sure what analog would be in UK. In the US vet cardiologists can be hard to find unless you live in a very big city. Our experience with even "radiologist specialist vets" has not been good, and I would never recommend spending the money with such a vet. I would probably give it a while and see what happens on vet next visit. Certainly not all murmurs are HCM and not all HCM cats even have murmurs.

Hi catlover,yep stress & infection are two of the main causes that the vet picks up heart murmurs from in both cats & dogs but when the animal improves then the murmur more often than not disappears,if stress related it is normally in the younger animal but as they get used to coming in although they still hate it the stress levels must reduce as the murmur very often is no longer audible.
Oh what a worry having pets is,you wouldn't be without them but....!

The most recent study is out of France:

Prevalence of the MYBPC3-A31P mutation in a large ... [J Vet Cardiol. 2010] - PubMed result

Abstract

OBJECTIVES: The MYBPC3-A31P mutation has been identified in the USA in a colony of Maine Coon cats with an autosomal dominant hypertrophic cardiomyopathy (HCM). The objectives of this prospective study were: 1) to evaluate the prevalence of this mutation in a large feline population from Europe; 2) to compare these data with the prevalence of HCM in the Maine Coon breed.

ANIMALS AND METHODS: 1) 3757 cats from different breeds including 2744 Maine Coon cats were screened for the mutation. 2) 164/2744 Maine Coon cats were subjected to echocardiography (Echo-Group, mean age = 2.6 years [0.3-11.5]).

RESULTS: 1) In the whole study population, the mutation was only found in Maine Coon cats (prevalence = 41.5%), except for one British Longhair cat. 2) 55/164 (34%) cats from the Echo-Group carried the mutation while only 12/164 (7%; 5/48 heterozygous, 5/7 homozygous mutated, 2/109 homozygous wild-type cats) showed HCM. MYBPC3-A31P was associated with a significant increased risk of HCM (relative risk = 9.91).

CONCLUSION: The MYBPC3-A31P mutation is highly prevalent in Maine Coon cats in Europe and appears to be breed specific with potential marginal events. Young unaffected mutated cats and affected homozygous wild-type cats illustrate the phenotypic and etiological heterogeneity of feline HCM, as demonstrated in humans.
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There was an extremely elevated incidence of HCM in Maine Coons homozygous for the mutation - 71%.

Thanks Ekimmel for taking the time to post. Unfortunately I'm finding it hard to decipher this information. What is a 'marginal event'? How do I know if my cat is mutated, or does that not matter? Could you explain the conclusion? Sorry for being a bit thick... but, help!

Nice to see some new research, and thanks for the post.

Originally Posted by Howlinbob

Unfortunately I'm finding it hard to decipher this information. What is a 'marginal event'? How do I know if my cat is mutated, or does that not matter? Could you explain the conclusion? Sorry for being a bit thick... but, help!

Let me take a shot at the above questions from reading the abstract...

The researchers assembled a population of 3757 European cats of which 2744 were Maine Coons.

They screened these cats for the known HCM mutation and found only one non-MC cat that tested positive. 41.5% of the MCs had the mutation (abstract does not say fraction with one copy, heterozygous, vs. two copies, homozygous). So this is largely a MC-specific health issue.

164 of the MCs were screened by echocardiogram to look for evidence of heart changes indicative of HCM. 55 (34%) of the echoed MCs had the mutation. Only 12 of the 164 cats showed evidence of HCM changes, broken down as follows: 5/48 heterozygous, 5/7 homozygous mutated, 2/109 homozygous wild-type cats (wild-type means free of the mutation).

So here the probability of MCs free of the mutation showing HCM changes was less than 2%, while the probability for hetero MCs was 10%, but for homo mutated cats it was 71%!

So again we see that homozygous MCs--those with two copies of the MYBPC3 mutation--are virtually certain to undergo structural changes of the heart consistent with HCM. How many of these will show symptoms and how many will die prematurely was not addressed by this study.

Hetero MCs fared much better, though I note that the median age of the echoed population of cats was stated as 2.6, which is quite young. If it was more like 5, we might have seen the hetero percentage be much higher (and the homo group be much smaller due to them having died!).

What does this tell a person thinking of buying a MC? In my opinion it tells them quite clearly that if they want to buy a MC that has the best chance to live a long and healthy life, they should absolutely avoid getting a kitten that was homozygous for the mutation, and most likely also avoid a hetero kitten.

The only thing I found surprising here was the claim that over 40% of European MCs carry the mutation. That makes buying from breeders that do not do HCM testing pretty risky.

As for how you can find out about your own cat, well ideally your breeder could tell you. However it is possible to have your cats tested with a simple mouth swab. Here is the original lab that does it (run by the person that discovered the mutation):
Cat DNA Tests from the VCGL at the College of Veterinary Medicine

Other labs now do the testing as well, though whether they are as reliable is probably an open question.