Broken Hearts
by JEANNE O'DONNELL, Donegal Himalayans
Published January 2015

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As breeders we face a whole host of obstacles, the least of which is producing that perfect cat.

Inheritance plays a role in so many factors, and it is often just a roll of the genetic dice that determines the outcome. Sometimes that outcome is devastating. One kitten may have the ideal head structure, but it fails to FIP (Feline Intestinal Peritonitis). Another may have a dynamite body, but it dies in your arms from a heart problem.

If we breed long enough, we will suffer the pain of a broken heart, both our own and that of some of our treasured feline companions. HCM (Hypertrophic Cardiomyopathy) is one such cause of this pain.

Hypertrophic Cardiomyopathy

In humans, researchers have discovered hundreds of mutations spread across a number of genes encoding for HCM. In cats, it hasn’t seemed quite as complicated. However, to date, there are only two breeds that have had some success in locating genetic markers for HCM. It was because of the discovery of mutations in cardiac myocin binding protein C genes associated with HCM in Maine Coons (A31P) in 2005 and in the Ragdoll (C820T) in 2007, that a DNA test was subsequently developed for those breeds.

So far, the Ragdoll’s genetic test seems to be fairly accurate. Unfortunately, the Maine Coon breeders have seen some positives develop that tested negative genetically for this disease. However, even that is a step in the right direction. And it’s a testimony that until we find a definitive marker for this disease in our breed, we must get cardiac ultrasounds on our breeding cats. There is nothing worse than getting a phone call or an email from a kitten buyer with the tragic news that their Himalayan or their Exotic or their Persian has just suddenly died, often without obvious signs. If breeders aren’t educating their clients about HCM, they will have no clue of the signs to look for, how to catch it early enough to treat it, and potentially extend that kitty’s life.

 

CH Donegal’s Tow The Line


CH Donegal's Tow The Line

My seal lynx point boy, CH Donegal's Tow The Line(aka Toby), is a good example.

Toby first exhibited labored breathing when being bathed for a show. His show agent assumed it was just the stress of getting a bath. Let’s face it, not all cats like being bathed.

Because I knew that Toby's sire, Ronan, was positive for HCM and I was more informed about the signs of HCM and its dominant mode of inheritance, Toby’s symptom was a cause for concern. His agent and I agreed that he should be tested for HCM.

So Toby received his first cardiac ultrasound at sixteen months of age, earlier than the recommended two years of age. He was positive for HCM, with enlargement already becoming evident upon ultrasound.

The veterinarian started him on daily Atenolol, a blood pressure medicine, and his ultrasound at four years of age showed a functional improvement. The enlargement is still there. That won’t go away. But the medicine helped to take the load off of the heart enabling it to pump more efficiently.

Ultrasound For HCM

So when is the right time to test by cardiac ultrasound for HCM? Baseline scans should begin at two years of age (recommended by veterinarian cardiologists) unless symptoms present sooner. A heart murmur can be a sign of HCM, particularly if it wasn’t present on previous examinations. Kittens will sometimes present with a murmur that goes away after six months of age. If a murmur is detected before that age, the kitten should be rechecked after it reaches six months. A murmur after that age should warrant further investigation with an echocardiogram (cardiac ultrasound) to rule out HCM or some other cardiac abnormality.

An echo, as it is often called, uses sound waves to view the pumping activity of the heart and the size of the chambers, including wall thickness. It is not to be confused with an ECG or EKG which is an electrocardiogram that measures the electrical activity of the heart. Typical symptoms of this disease are deep chest breathing, lethargy or inactivity uncharacteristic for the age of the cat, exercise intolerance, and saddle thrombosis (hind leg paralysis due to a blood clot). In its more developed phase, the cat will develop CHF (Congestive Heart Failure) with one or more of these symptoms. Different medications are given for cats who have HCM without compromised function verses those with compromise (i.e. beta blocker for functional cats verses an ace inhibitor with diuretic and Vetmedin for cats in CHF). Originally developed for dogs, Vetmedin (Pimobendan) is literally a life saver for CHF cats. At the time of this writing, my twelve year old Himalayan, Irish, is a six year survivor of CHF on that drug, Enalapril, and Furosemide.

It is important that cardiac ultrasounds be administered by someone well versed in diagnosing HCM. A positive result on either the genetic tests (currently only available for Maine Coons and Ragdolls) and/or cardiac ultrasound (any breed) should be considered definitive and those cats should be eliminated from any breeding program. Cats that are positive for HCM should be monitored by echocardiogram at six month to one year intervals (depending on severity of the HCM) for disease progression and medication requirements. Negatives for HCM should be retested by ultrasound at least every other year in the event of a testing error or a new, spontaneous genetic mutation, which is rare but possible.

A negative may not always mean negative, meaning that those cats with normal ultrasounds are considered negative merely at that point in time, with a possible exception in Ragdolls via genetic testing. In the research for HCM mutations in the Maine Coons, one mutation was discovered and a test was provided for that mutation. However, some of those negative cats later went on to develop HCM, detected by cardiac ultrasounds. So in that breed, there is more than one mutation responsible for HCM. The Ragdoll mutation called R820W has been fairly accurate in identifying HCM cats. So each breed is unique and may have one or more markers for this disease.

DNA Tests For HCM

Regarding the current genetic testing in those two breeds, and hopefully a future test for HCM in Persian cats, another example of a “false” negative would be if the DNA on that cat was marked correctly before being sent and/or was documented by the lab accurately. Testing is managed by humans and human error is possible. Many of us saw what happened at a lab years ago in contract with the Cat Fanciers’ Association, when we received erroneous DNA test results. Many breeders are not aware that the coalition with that researcher (Dr. Melba Ketchum, DNA Diagnostics dba Catgenes) was dissolved and the DNA was sent to Ernest (Gus) G. Cothran, DVM, PhD at Texas A&M Veterinary Genetics Lab (www.catDNAtest.org).

 

Dr. Cothran is now developing cat DNA genotyping that will offer hundreds more markers than previously available. And it is that very researcher, Dr. Cothran, who initiated the Persian HCM study that Donegal Cattery has contributed DNA to since 2008. At the time of this writing, the DNA profile testing which had been available online is currently unavailable while the lab installs new testing modalities involving this new state of the art genetic testing.

Based upon historical research in those two breeds of cats and in humans, it has been postulated that HCM is primarily a genetic mutation with autosomal dominant genetic inheritance. Simplistically defined, it is mutations in genes that code for structural proteins. In the case of HCM it is the structural proteins that build sarcomeres in the heart, affecting its structure over time. The sarcomeres “tell” the heart muscles to grow abnormally large, eventually causing the heart to fail by either sudden cardiac death or congestive heart failure. It is considered to be autosomal dominant but with variable penetrance, because it can develop at various points in a cat’s life with varying degrees of symptoms. It typically strikes symptomatically at middle age (somewhere between six and eight years of life), but some will have symptoms as young as kittens, less than a year of age. It has been postulated also that there may be mild forms and malignant forms of the disease.  

Given the similarities in the historical data, some predictions can be postulated for the statistical potential for inheritance in the Persian breed, which includes Himalayans. Further research will be required for a definitive predictive capability. We are familiar with this projected rate of inheritance with our experience with PKD (Polycystic Kidney Disease).


Heterozygosity and Homozygosity of HCM are discussed in the articles below:


Feline Hypertrophic Cardiomyopathy:  Genetics and HCM
Authors:                                                                                                                                      
Mark D. Kittleston, DVM, PhD, Diplomat ACVIM (Cardiology),
Jody A. Chinitz
,
Marcia J. Munro                         

NOTE:  A portion of this article and its online reference is quoted below by permission. The entire article may be viewed at https://web.archive.org/web/20140723170353/http://mysite.verizon.net/jachinitz/hcm/genetics.html    

“It was originally thought that homozygous individuals would not survive (would die in utero or be stillborn) but it is now well established that cats (and humans) that are homozygous for a mutation do survive. They add another level of complexity to the disease. When a cat that is homozygous for one of the mutations is bred to a cat without a mutation all of the kittens in a litter will be heterozygous for the mutation and so have the potential for developing HCM and, even if they don’t, can still pass the mutation on to descendants. When a cat that is homozygous for a mutation is bred to a cat that is heterozygous, on average, 50% of the kittens will be homozygous and 50% will be heterozygous. Obviously, if two homozygous parents are bred, all of the kittens will be homozygous.”



As described in the article above, each kitten inherits a gene from each of its parents that determines whether it will or will not develop HCM. (the gene is present or not present, for example, as in the PKD tests with which we are so familiar).

  • A cat is Heterozygous ( -/+ or N/P) for the HCM mutation if it received the HCM gene from only one parent.
  • A cat is Homozygous (+/+ or P/P) for the HCM mutation when it received a copy of the HCM gene from EACH parent .

In a publication in May, 2004, the following researchers authored a joint paper on this disease. The following reference discusses symptomatic expression of HCM and the need for breeder involvement in research efforts.


Feline Hypertrophic Cardiomyopathy:   Advice for Breeders
Authors:                                                                                                                                      
Mark Kittleston, DVM, PhD, DACVIM (Cardiology) at UC Davis in California,                                         
Rebecca Gompf, DVM, PhD, DACVIM (Cardiology) at the University of Tennessee,                                                       
Susan Little, DVM, DABVP, at the Winn Feline Foundation
NOTE:  A portion of this article and its online reference is quoted below by permission.
Ref.
http://www.2ndchance.info/hyperthyroid-cardiomyopathyKittleson2004.pdf

“In Maine Coons and American Shorthairs, HCM has been confirmed as an autosomal dominant inherited trait, as it is in humans where over 130 gene mutations in 10 genes have been found to cause the disease. The disease has variable expression; meaning some cats are severely affected, others are only mildly to moderately affected, and some cats may not have evidence of the disease yet produce affected offspring….

In the long term, we will need a genetic test for HCM in each breed. A genetic test would allow us to identify affected cats before they were bred and do so accurately. Since the disease is inherited as an autosomal dominant trait, once a mutation is identified, if all breeders cooperated by testing their breeding cats for the mutation the disease could be eliminated from the breed within several generations. However, the money and resources necessary to identify the gene or genes and to develop a genetic test for each breed are scarce in veterinary medicine. Breeders and cat fanciers can help by supporting research through organizations such as the Ricky Fund established by the Winn Feline Foundation.”


The Winn Feline Foundation

Winn Feline Foundation provides the predominance of feline research grants and is a non-profit organization. To issue a grant for a breed-related research study, there has to be a stipulated fund that must raise a minimum of $15,000 within five years or the funds are transferred to the general fund. If that minimum is reached within the allotted time frame, the money within that stipulated fund may be awarded to a researcher in the form of a grant.

NOTE:  The Ricky Fund, while a worthwhile endeavor that helped to pave the way for the Persian HCM Fund, is designated for general HCM research funds. The Breed Norwegian Forest Cat Fund is specifically for HCM research in the Norwegian Forest Cat breed.

When making a donation through Winn Feline Foundation, you must select the Persian HCM Fund to make sure your donation is appropriately allocated for research in Himalayans and Persians. 

Genomic Sequencing

 

In a recent conversation with Dr. Glen Olah, President of Winn Feline Foundation, I learned that there is a new field of affordable research (Genomic Sequencing) that will yield thousands of bits of genetic information. It is hoped that this type of DNA mapping will lead to unlocking the genetic code for HCM in the various breeds.

One such study is already in process for the Sphynx breed with Dr. Kathryn M. Meurs, DVM PhD in an effort called Hairless Hearts.

Dr. Olah made a phone call to Dr. Meurs on behalf of the Persian HCM Research Fund and subsequently put me in touch with her. I had a detailed conversation with Dr. Meurs in early December 2014 about the six year history of our efforts with funding the current Persian HCM Research project (Ronan’s Big Heart).

That project is the coalition with Ernest (Gus) G. Cothran, Jr., DVM PhD at VIBS (Veterinary Integrated Biosciences, Texas A&M University) initiated in 2008 which began using buccal swabs. Scores of DNA from Donegal Cattery have been banked at this research facility, most of which are from Himalayan cats and CPCs (Colorpoint Carriers). Unfortunately, a lack of adequate funding had set this study on the back burner.

We do have a window of hope, however. That conversation with Dr. Meurs led to a second coalition for Persian HCM Research using the new state of the art Genomic Sequencing. The first three subjects’ data and bloodwork were sent to NC State Veterinarian Laboratory on December 15, 2014. We need a minimum of five subjects for this study, but if we have more, Dr. Meurs will welcome what we can provide. This study will involve Himalayans as well as Persians that have no Himalayans documented in their five generation pedigree.


CH Donegal’s Irish Crème

CH InTheWind Peadar Ronan of Donegal was the reason for Project Ronan’s Big Heart. His son, CH Donegal’s Irish Crème, was the first case of HCM diagnosed at Donegal Cattery, the first DNA contribution to Dr. Cothran’s research at Texas A&M in 2008, and one of the first three submissions to Dr. Meurs study at NC State in 2014.

We are just at the beginning phase, so it is unknown whether or not Exotics will also be included. With this type of breed to breed comparative study, it is likely they will be requested at some point, especially since American Shorthairs have also been affected by HCM. If you have positive Exotics (cats with documented cardiac ultrasound enlargement due to a diagnosis of HCM) and would like to have them included, I will bring your offer before Dr. Meurs. If she decides to include them, I will let you know how to participate. It will involve 1-2ml. of blood in a purple top EDTA tube, wall thickness measurements from the cardiac ultrasound while the heart is in diastole, and a copy of the pedigree.

Project Ronan’s Big Heart was initiated to establish a fund for Persian HCM Research, regardless where the funds are appropriated. Winn Feline Foundation receives a grant proposal from the researcher (in this case perhaps from two researchers), then they decide who is awarded the grant. You can read about this project by going to Winn Feline Foundation’s web site on their Ways to Give page. Then click on the Stipulated Funds and scroll down to the Persian HCM Research Fund.

When you donate, make sure where it says on the form “How would you like your funds used?” you select:  “I would like to choose a specific purpose or fund.” Where it says “Specific Purpose” select Persian HCM Fund. Remember, the Ricky Fund HCM is for general HCM research. It is not breed specific. And the Norwegian Forest Cats HCM Fund is specifically for that breed.

Funding as of January 1, 2015

As of January 1, 2015, we have received donations of $10,066  towards funding the research to identify the gene in Persian cats that causes HCM. That means we are more than 2/3 of the way to reaching our goal of $15,000 to fund the research!

Facebook & Yahoo Groups

To keep up to date on the latest research regarding and the funding status join our Yahoo or Facebook pages:

A Final Appeal

If you are not a part of this potential for a solution by giving financially and/or participating in the research, then you are merely a part of the problem.

We will all face HCM in our breeding programs eventually, just as we did with PKD.

But if we get behind this research, and if it leads where the researchers hope it will lead, we will one day be able to have the confidence that we are providing our clients, including other breeders, and Himalayan and Persian cats with healthy hearts—not broken ones.

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