HCM – Hypertrophic Cardiomyopathy
What is HCM? – Hva er HCM?
HCM is a heart disease that can be found in all cats, also housecats, and it is in fact the most common heart problem in cats. Hypertrophic Cardiomyopathy means thickening of the heart walls, that make the heart ineffective. The heart can stop, or the cat can get blood clots and die.
If discovered, there is medication and treatment. Also it is good if the cat is not overweight. Some cases of HCM can give sudden death, while some cats can live long in spite of HCM diagnosis. Fox 2018 indicates the following numbers:
- around 6-7 % will die within the first year
- around 28-30 % will die within ten years
- 10 % can live to over 9-15 years age
HCM er en hjertesykdom som fins hos alle katter, også vanlige huskatter. Det er den vanligste hjertelidelsen hos katt. Hypertrofisk kardimyopati betyr at hjerteveggene fortykkes, og gjør hjertet lite effektivt. Hjertet kan da stoppe, eller katten kan utvikle blodpropp.
Om HCM oppdages fins det medisiner og behandling. Det er også best om katten ikke er overvektig. Noen tilfeller av HCM gir brå død, mens andre varianter utvikler seg veldig sakte. Noen katter kan leve lenge tross diagnosen. Fox 2018 anslår de følgende tallene:
- omkring 6-7 % dør det første året
- omkring 28-30 % vil dø innen ti år etter sykdommen starter
- 10 % kan leve til over 9-15 år alder
HCM in Maine Coon
In Maine Coons, a related colony of cats affected with HCM was studied to discover more about this illness (Meurs 2006), and there has been more research in our breed than other breeds. This does not mean HCM is only found in Maine Coons, but we know a lot more about it than for other breeds at risk.
- Approximately 10 % of Maine Coon (2018 numbers) carry a mutation that increases risk of getting HCM
- Approximately 5-15 % of Maine Coons will develop HCM during their life
- Offspring of tested lines have much lower risk than offspring of non-tested lines
What to do – Hva bør man gjøre?
Breeders should follow the rules of the PawPeds health programme for HCM, with regular screenings of breeding cats. No one can claim “HCM free” lines, but all breeders can do their best to limit this disorder.
Alle oppdrettere bør følge PawPeds helseprogram for HCM, med jevnlige undersøkelser av avlskatter. Ingen oppdrettere kan påstå å ha “HCM-frie” linjer, men alle oppdretter kan gjøre sitt beste for å begrense forekomst av denne lidelsen.
HCM health programme – DNA testing and echocardigraphy
Both ultrasound screenings and known DNA-status for A31P is necessary for breeding cats.
We scan (ultrasound) our breeding animals according to the PawPeds health programme, with scans by a veterinary specialist, see list of PawPeds approved veterinary cardiologists. All results from these scans are publically available in the PawPeds Maine Coon database.
All our cats are negative for the HCM1-A31P DNA mutation.
Både ultralyd og DNA-testing er nødvendig for avlskatter.
Vi hjertescanner våre avlskatter etter PawPeds’ helseprogram, med ultralydundersøkelser hos hjertespesialist, se egen liste over PawPeds-godkjente kardiologer. Alle resultater fra disse er offentlig tilgjengelige i PawPeds Maine Coon-database online.
Alle våre katter er negative for A31P-mutasjonen.
Ultrasound – echocardiography
To check for HCM it is necessary to scan for clinical HCM through ultrasound (echocardiography), and this test needs to be repeated several times in a cat’s life. The most important is to first scan young breeding cats before they are mated the first time, in order to leave the most serious cases who get HCM early out of breeding. Then also very important is to scan middle aged or older breeding cats (over 7 years), as most cases of the disease usually develops quite late in life.
Recommendations are ultrasound scans repeatedly through the cat’s life:
- at 1 year’s age and at least before breeding
- 2 years age
- 3 years age
- 5 years age
- after 7 years of age, 8-9 is very good
For å undersøke katten for klinisk HCM er det nødvendig å utføre ultralyd hos spesialist på hjerte, og denne undersøkelsen må gjentas flere ganger gjennom kattens liv. Det viktigste er først å scanne unge avlskatter før paring, slik at de alvorlige tilfeller med HCM i ung alder kan tas ut av avl. Det er også svært viktig å scanne de middelaldrende og eldre avlskatter (over 7 år), ettersom de fleste tilfeller av sykdommen vanligvis utvikles sent i livet.
Helseprogrammets anbefalinger er gjentatte hjertescanninger gjennom kattens liv:
- ved 1 års alder og før første paring
- 2 års alder
- 3 års alder
- 5 års alder
- etter 7 års alder, 8-9 er veldig bra
A heart ultrasound scan shows the heart’s status at that date and age. It is therefore important to follow the recommendations of continued HCM-ultrasounds, as the cat gets older, and especially at high ages. Some critics claim that a heart scan shows only “a moment in time”, but that means they have not quite understood how HCM works. “Still healthy heart at this age” is a better formulation, and describes also why continued scans are needed, and why they are more valuable the older the cat is.
En hjerteultralyd viser hjertets status pr den dato og alder katten har undersøkelsesdagen. Det er derfor viktig med fortsatte HCM-undersøkelser, etter hvert som katten blir eldre, og det viser viktigheten av å undersøke på nytt ved høy alder. Enkelte kritikere påstår at en hjerteultralyd bare er “et øyeblikksbilde”, men det viser at de ikke har forstått hvordan HCM virker. Det er mer korrekt å si “fremdeles friskt hjerte ved denne alder” – og jo eldre katten er, desto viktigere er resultatet.
Challenges for the Breeder – Utfordringer for oppdretteren
HCM is hereditary, but only one cause, mutation is known, and we know there must be other mutations also not yet known.
- HCM can be “late onset”, meaning no symptoms at all until the cat is 4-5 years old
- many breeders scan only young cats, under 3 years old
- HCM scans before breeding and at under 2 years of age, will only discover the “early onset” cases
- HCM seems to sometimes skip a generation and then reappear in offspring of the next generation
- most cats who die early will not have autopsies, so cause of death will remain unknown
DNA-test: A31P – HCM1
Most Maine Coon breeders test for the one known factor that can cause HCM, the A31P mutation in the MyBPC3 gene, often called HCM1. This genetic test is only one indication of risk of getting ill with HCM later in life, but it seems to be responsible for many of the cases. Cats who have “double” of the affected gene (homozygous positive) have a very high risk of getting ill, and a slightly higher risk is also seen in those with one gene (heterozygous positive), but these cats will typically stay healthy until at least 4-5 years old and those who get ill might not be as seriously affected (Longeri 2013).
- N/N: normal risk (around 5 %)
- N/A31P HCM: almost 2 times risk
- A31P HCM/A31P HCM: around 18 times risk
There are cats who suffer from HCM who are N/N (negative) for the MyBPC3 A31P gene, implying that there must be other yet undiscovered factors involved. In the future there will hopefully be yet further HCM-mutations discovered to test for. There is ongoing research.
Patterns of matings:
It is very important to know A31P (HCM1-DNA) status to avoid homozygous positives who have a very high risk of illness.
Review study of all the research done on A31P and HCM in Maine Coons
Read my article (review study) on HCM/A31P in MCO and research:
Berge. 2014. “A31P DNA-test and HCM in Maine Coon.”
Berge. 2014. “A31P DNA-test og HCM-sykdom hos Maine Coon”
List of reference papers with links to full text under Research papers below.
Excerpt with findings
Comparing the numbers from all the research studies (table 2), a more complete picture can be seen. The number of cats in a study, the gene frequency of A31P for those cats, and the number of affected cats can all influence the results of a single study.
Wess who concluded that A31P had no effect on HCM, also had the smallest study, and the gene frequency for A31P in his study was significantly lower in his study than in all the other studies. The number of cats diagnosed with HCM was also higher than the supposed prevalence for HCM in the breed. This could have influenced the conclusion. Longeri who also did a meta study based on Longeri, Mary and Wess arrived at similar numbers that we see in table 2 regarding disease prevalence and gene frequency.
Summed up these studies show:
- Homozygous cats have a highly increased risk to get HCM, with few cats without signs of illness at 4-5 years of age.
- Heterozygous cats also have an increased risk, but the disease strikes much later and often after 5-8 years of age. Over half of the cats are healthy at 5 years of age.
- A high number of the HCM-affected Maine Coons do have this mutation.
Summary and Conclusion
Summing up the results of all the studies, it is clear that there is a strong correlation between the A31P mutation and development of HCM. It is also clear that HCM is found among cats without this mutation, so there are other causes in addition to A31P.
Both DNA-testing with a gradual selection away from the mutaton from the gene pool, and repeated ultrasound scans (echocardiography) by a cardiologist are necessary to limit the cases of HCM in the Maine Coon breed.
Research papers on HCM – Forskning og studier:
HCM and the A31P mutation in Maine Coon
- Carlos Sampedrano, Carolina. et al. 2009. “Prospective echocardiographic and tissue Doppler imaging screening of a population of Maine Coon cats tested for the A31P mutation in the myosin-binding protein C gene: a specific analysis of the heterozygous status.” In: Journal of Veterinary Internal Medicine. 2009; 23:91–99
- Fries R, et al. 2008. “Prevalence of the Myosin-binding Protein C Mutation in Maine Coon Cats.” In: Journal of Veterinary Internal Medicine. 22:893-896, 2008.
- Godiksen, Mia. et al. 2013. “Feline Hypertrophic Cardiomyopathy Associated with the p.A31P Mutation in cMyBP-C Is Caused by Production of Mutated cMyBP-C with Reduced Binding to Actin.” In: Open Journal of Veterinary Medicine, 2013, 3, 95-103 doi:10.4236/ojvm.2013.32016 Published Online June 2013
- Godiksen, Mia, et al. 2011. “Hypertrophic cardiomyopathy in young Maine Coon cats caused by the p.A31P cMyBP-C mutation–the clinical significance of having the mutation.” In: Acta Veterinaria Scandinavica 2011, 53:7
- Gundler, Suzanne, et al. 2008. “Prevalence of myocardial hypertrophy in a population of asymptomatic Swedish Maine coon cats.” In: Acta Veterinaria Scandinavica. 2008, 50:22 doi:10.1186/1751-0147-50-22
- Longeri, Maria. et al. 2013. “Myosin-Binding Protein C DNA Variants in Domestic Cats (A31P, A74T, R820W) and their Association with Hypertrophic Cardiomyopathy.” In: Journal of Veterinary Internal Medicine 10.1111/jvim.12031
- Mary Jérôme, et al. 2010. “Prevalence of the MYBPC3-A31P mutation in a large European feline population and association with hypertrophic cardiomyopathy in the Maine Coon breed.” In: Journal of Veterinary Cardiology (2010) 12, 155e161.
- Meurs, Kathryn, et al. 2005. “A cardiac myosin binding protein C mutation in the Maine Coon cat with familial hypertrophic cardiomyopathy.” In: Human Molecular Genetics (2005) Vol.14, No. 23, doi:10.1093/hmg/ddi386.
- Wess, Gerhard, et al. 2010. “Association of A31P and A74T polymorphisms in the myosin binding protein C3 gene and hypertrophic cardiomyopathy in Maine Coon and other breed cats.” In: Journal of Veterinary Internal Medicine. 2010; 24:527–532.
Other HCM research
- Fox, Philip R. et al. 2018. “International collaborative study to assess cardiovascular risk and evaluate long-term health in cats with preclinical hypertrophic cardiomyopathy and apparently healthy cats: The REVEAL Study.” In: Journal of Veterinary Internal Medicine. April 2018 DOI: 10.1111/jvim.15122
- Freeman, Lisa M. et al. 2013. “Body size and metabolic differences in Maine Coon cats with and without hypertrophic cardiomyopathy.” In: Journal of Feline Medicine and Surgery 2013 15: 74
- Meurs, Kathryn, et al. 2007. “A substitution mutation in the myosin binding protein C gene in Ragdoll hypertrophic cardiomyopathy.” In: Genomics 2007; 90:261–264.
- Trehiou-Sechi, Emilie, et al. 2012. “Comparative echocardiographic and clinical features of hypertrophic cardiomyopathy in 5 breeds of cats: a retrospective analysis of 344 cases (2001-2011).” In: Journal of Veterinary Internal Medicine. 2012 May-Jun; 26(3):532-41. doi: 10.1111/j.1939-1676.2012.00906.x.
- PawPeds Health Programme for HCM, started by Maine Coon-katten breed society in January 2004.
- IG Herzgesunde Katzen, interest group for heart disease in cats, founded 2012 in Mannheim.
- IG Herzgesunde Katzen’s summary of PawPeds statistics on HCM
I happen to feel that the degree of a person’s intelligence is directly reflected by the number of conflicting attitudes she can bring to bear on the same topic.
– Lisa Alther