Mitral Valve Disease Breeding Protocol
for the Cavalier King Charles Spaniel


Early-onset mitral valve disease has been found to be "highly heritable" in the Cavalier King Charles spaniel breed, and "selection against the disease should be successful.", according to an April 2011 research report.

Veterinary specialists have designed breeding guidelines to eliminate early-onset mitral valve disease in Cavalier King Charles spaniels in the United States and the United Kingdom. The guidelines (called the MVD Breeding Protocol) were strongly advised to US breeders in 1998 (and in 1996 to UK CKCS breeders) by a group of veterinary cardiologists and a geneticist who had dedicated years of study to mitral valve disease in Cavaliers.*

*In other countries, veterinary cardiologists and geneticists have designed similar breeding guidelines, either by auscultation (listening to the flow of blood through the mitral valve using a stethoscope), as in Canada and Sweden, or by electrocardiograph (ultrasound), as in France.

Both the UK's Cavalier King Charles Spaniel Club and the Cavalier King Charles Spaniel Club of Canada have endorsed the MVD Breeding Protocol.* In 2001, the Swedish Kennel Club introduced a modified, but mandatory version of the MVD Breeding Protocol for all cavaliers, and in 2011, the Dutch Kennel Club introduced its own mandatory, modified version of the MVD Breeding Protocol for all CKCSs being bred. The Cavalier King Charles Spaniel Club, USA endorsed the full MVD protocol from 1998 to 2010, when the leadership of that club decided to replace the protocol with a fictitious, watered-down version which no panel of veterinary cardiologists has ever recommended and is destined to fail.

 *However, neither the UK CKCS club nor the Canada CKCS club requires that the dogs be examined by veterinary cardiologists.

Since 1998, only an insignificant minority of breeders of Cavalier King Charles spaniels in the United States have followed these guidelines. In the 13 years since then, the vast majority of such breeders have squandered at least three generations (at 2.5 years per generation) of Cavaliers towards eliminating early-onset (onset before age 5 years) mitral valve disease.* By shunning the MVD Protocol and actually increasing the breedings of Cavaliers in violation of the MVD Protocol, the great majority of American breeders have acted irresponsibly and in callous disregard for the health and welfare of future generations of Cavaliers.

*For example, in 2010, 55% of all cavalier litters registered with the UK Kennel Club had at least one parent under the age of 2.5 years.

MVD Breeding Protocol

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In Depth

-- history of the protocol

The MVD Breeding Protocol has been designed to eliminate early-onset mitral valve disease. Veterinary cardiologists throughout North America and Europe conducted studies of MVD in Cavaliers in the 1990s.

Dr. James Buchanan, Penn Vet SchoolBruce KeeneA group of four world renowned veterinary cardiologists, Doctors Andrew Beardow from England, James Buchanan (right) from the United States, Virginia Luis Fuentes from Scotland, and Bruce Keene (left) from the US, and an internationally respected geneticist, Professor Lennart Swenson from Sweden, each presented reports on the results of their professional studies about the disease in1998. Their conclusions:

• MVD is the leading cause of death in cavaliers;
• It is a hereditary, genetic disorder;
• There has been no statistical improvement in cavaliers' mitral valves in the eleven years since the first studies; and
• The disease can be decreased and the age of onset delayed by following guidelines of only breeding cavaliers who are over the age of 2.5 years, have hearts free from MVD murmurs, and have parents whose hearts were MVD murmur-free at age 5 years. No cavaliers should be bred which have murmurs before age 5 years.

Anne Eckersley RobinsThese experts presented their findings and conclusions at a symposium in May 1998, which was sponsored by the Cavalier King Charles Spaniel Club, U.S.A. (CKCSC,USA).* Under the leadership of its then president, C. Anne Eckersley-Robins (left), the board of directors of the CKCSC,USA then also endorsed the MVD Breeding Protocol in 1998.

* A similar presentation was made in November 1996 before the UK Cavalier King Charles Spaniel Club.

Professor Lennart SwensonThese guidelines were developed by the Swedish Kennel Club, and are based upon that club's successful efforts to reduce hip dysplasia in Rottweilers. Between 1976 and 1994, the percentage of Rottweilers diagnosed with hip dysplasia decreased from 36% to 11% by following a similar breeding program. Professor Swenson (right) reported that hip dysplasia is a multifactorial, polygenic trait, and it is believed MVD is also.

He pointed out that it is not realistic to expect to eliminate the causes of mitral valve disease by any breeding program without further research into the reason for the high prevalence of the disorder in cavaliers. Instead, the goal is to postpone the onset of the disease so that all cavaliers die a natural death before MVD becomes a health problem.

Professor Swenson believes that if the recommended breeding guidelines are followed by all breeders, we would see improvement after the first generation and significant progress towards delaying the onset of MVD over two to three generations. Mitral valve disease is not controlled by a single gene, but there may be one dVirginia Luis Fuentesominant gene which controls the worst (earliest onset) 30% of MVD cases. He stated that if that is correct, this worst gene would be the first one to disappear once the breeding guidelines are universally followed.

Dr. Luis Fuentes (right) reported on the British studies, which began in 1987 and showed that 50% of all 5 year old cavaliers had MVD murmurs, and all examined Cavaliers over the age of 10 had murmurs. The English Cavalier King Charles Spaniel Club has endorsed the Swedish guidelines, and it also is publishing a registry of all cavaliers over age 5 years with murmur-free hearts.

Andrew BeardowDr. Beardow (left) explained that the guidelines call for each breeding cavalier to be examined annually by a veterinary cardiologist using a stethoscope. He said that, compared to an echocardiographic examination, the use of a stethoscope (called auscultation) by a cardiologist is 90% accurate in detecting MVD. In view of the relative wide availability and low cost of auscultation diagnosis, it is preferred over more expensive alternatives. Compliance with the guidelines is enhanced by using relatively inexpensive, simple, and effective measuring methods. Also, the speakers expressed their concern that the testing device be specific enough to identify MVD but not so sensitive as to eliminate all of the breeding stock.

Most importantly, the experts emphasized that, to be effective, the breeding guidelines must be widely supported and uniformly implemented. The biggest reason that breeding guidelines fail is that the breeders do not follow them. Therefore, the results of the tests should be published for all to see. The English Cavalier Club's registry of murmur-free dogs is aimed at encouraging breeders to follow the guidelines.

A printable abridged version of the transcript of the May 1998 MVD symposium proceedings is available online, or send your name and postal (street and street number) mailing address to Editor@CavalierHealth.org for a full verbatim transcript to be mailed to you.

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-- since the 1998 symposium

--- United States cavalier clubs

CKCSC,USA Up-Side-DownThe board of directors of the Cavalier King Charles Spaniel Club, USA (CKCSC,USA) promptly endorsed the MVD Breeding Protocol as recommended guidelines in May 1998, the same weekend that the MVD symposium was presented to its club members. The club also started a registry of all cavaliers which were certified to have been murmur-free over the age of five years, called the CKCSC,USA Health Registry. However, in 2002, the CKCSC,USA began ignoring the protocol, including removing it from the club's Internet website and firing its Health Registry secretary. In 2010, the CKCSC,USA's board pretended that it had never endorsed the protocol in 1998 and approved a set of worthless breeding guidelines which no cardiologist ACKCSC Up-Side-Downresearchers had ever suggested would be effective. See here for details.

The American Cavalier King Charles Spaniel Club (ACKCSC), which is the cavaliers' parent club in the American Kennel Club (AKC) has never acknowledged the existence of the MVD Breeding Protocol. See here for details.

--- CKCSC of UK

UK Cavalier ClubThe United Kingdom CKCS club's version of the MVD Breeding Protocol does not require that veterinary cardiologists perform the stethoscopic examinations for heart murmurs, although it does require that cavaliers over the age of five years be examined by cardiologists in order to qualify for inclusion on the club's "Over Five" list.

Since the 1998 report, studies conducted by veterinary heart and genetic specialists have confirmed the efficacy of the MVD Breeding Protocol. In a 2000 research study of 4,255 CKCS heart examinations, Dr. James Wood of the Animal Health Trust in the United Kingdom reported that:

• MVD is the major killer of cavaliers under 10 years of age.
• Veterinary cardiologists were better able to identify early mitral valve murmurs than were non-specialist veterinarians.
• The parent's heart status can predict the offspring's future heart status.
• The offspring were ten to twenty times more likely to be free of MVD murmurs if the sire's heart was clear of murmurs at ages nine to eleven years.

In a 2009 report by UK veterinary cardiologist Simon Swift to the UK's Cavalier Club, he stated that 50% of cavaliers still are developing MVD murmurs by their fifth birthday. This is because most breeders are not following the MVD breeding protocol.  At the November 2010 "Cavalier Health Day", sponsored by the UK Cavalier Club, Mr. Swift reiterated the importance of breeders following the MVD breeding protocol.  He told the assembled breeders that the protocol was "rigorous advice that should be properly followed."

As recently as 2009, the chairman of the UK's Cavalier King Charles Spaniel Club stated: "There are many members who are still not prepared to health check their breeding stock, and of those who do, it would appear that many would not hesitate to breed from affected animals."

--- CKCSC of Canada

Cavalier Club of CanadaOn the bright side, since 2011, the Canadian cavalier club has endorsed the MVD breeding protocol. On its website, it states:

"The Cavalier King Charles Spaniel Club Of Canada has recently included the recommendation within its Breeders' Guidelines that Breeders breed Cavalier King Charles Spaniels that are at least 2.5 years old and murmur-free that have parents that were murmur-free at age 5 years."

However, the Canadian club's version of the MVD Breeding Protocol does not require that veterinary cardiologists perform the stethoscopic examinations for heart murmurs.

--- Swedish Kennel Club

Swedish Cavalier ClubThe Swedish Kennel Club and the Swedish Cavalier King Charles Spaniel Club follow a mandatory modified version of the MVD Breeding Protocol. In Sweden, to be eligible for breeding, all cavaliers must be tested clear of MVD murmurs at age 24 months, and their parents must have been tested clear of MVD murmurs at age 48 months. This breeding protocol was begun in 2001 and, ironically, is weaker than the MVD protocol devised by Swedish veterinary geneticist Lennart Swenson.

Dr. Jens Häggström & CavalierThe Swedish clubs do not require that all stethoscopic examinations of the cavaliers' hearts be performed by veterinary cardiologists, which is a requirement of the MVD Breeding Protocol. However, all Swedish veterinarians who are licensed to issue clear-heart certificates for this registry must pass an auscultation examination conducted by Sweden's top cardiologists/researchers, Drs. Jens Häggström (left) and Clarence Kvart (below).

Dr. Clarence KvartIn a 2010 study by cardiologist Dr. Clarence Kvart of the mandatory Swedish CKCS club breeding protocol, Dr. Kvart reports that that the prevalence of MVD in six-year-old cavalier King Charles spaniels, born 2001 and 2003, is at least 50% and lacks signs of decrease despite the current breeding program introduced in Sweden 2001.  The Swedish clubs have declined to toughen their program to match Prof. Swenson's recommendation.

Nevertheless, in 2012, the Swedish Kennel Club reported that of 988 cavaliers tested in 2012 for mitral valve disease, only six under the age of four years had murmurs, and only 61 of all of them had murmurs.

--- Dutch Kennel Club

Cavalier Club NederlandSince 2011, the Dutch cavalier King Charles spaniel club (Cavalier Club Nederland) and the Dutch Kennel club also have been following a mandatory modified version of the MVD breeding protocol. In theirs, all breeding stock cavaliers must have their hearts examined by ultrasound at age one year or prior to breeding. Thereafter, their hearts must be re-examined by auscultation by a specialist. If a mitral valve murmur is detected before the dog's fifth birthday, it may not be bred.

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-- cavalier breeders' objections

Breeders' Thumbs Down!Since 1998, only an insignificant minority of breeders of cavalier King Charles spaniels in the United States have followed the MVD breeding guidelines. In the fifteen years since then, the vast majority of such breeders have squandered at least six generations (at 2.5 years per generation) of cavaliers towards eliminating early-onset (onset before age 5 years) mitral valve disease.

We now find some cavalier breeders who claim to be following an MVD breeding protocol which turns out not to be the MVD Breeding Protocol. Some breeders have made up their own watered-down breeding protocol (something like: "try to breed" females over 2 years of age and MVD-clear, to males over 6 years and MVD-clear), which makes breeding decisions much easier for them, but which totally ignores the many years of statistical research and cardiologists' and geneticists' recommendations which has led to the MVD Breeding Protocol.

ACKCSC Up-Side-DownThe American Cavalier King Charles Spaniel Club (ACKCSC), which is the CKCS parent club of the American Kennel Club (AKC) has pointedly ignored the MVD breeding protocol and has gone so far as to even concoct a fictitious MVD breeding guideline of its own. On its website (as of this writing in 2013), the ACKCSC has stated:

"Currently, the recommended practice is to wait until a Cavalier is two years old or older before the first breeding and to know the parents and ancestral cardiac status. Cavaliers with early onset presentations of MVD (before four years of age) should not be bred and breeders need to work with the guidance of their cardiologists."

Instead of not breeding until age 2.5 years, ACKCSC claims in its baseless "recommended practice" to start breeding at 24 months, and it also shortens the definition of early-onset MVD from five years to four years. Instead of requiring that all four parents of the breeding pair be certified to be murmur-free by age five years, ACKCSC says its "recommended practice" is simply "to know the parents and ancestral cardiac status." That is a meaningless phrase apparently designed to provide AKC breeders with "cover" for ignoring the real MVD breeding protocol. It allows them to claim that, in their "wisdom" as experienced breeders, they "know the parents" and they have taken into account the "ancestral cardiac status".

The ACKCSC, as the AKC's parent club for cavaliers, has been assigned by AKC the responsibility of "the education of breed owners on the nuances of the breed, and overseeing the breed's health and welfare." So, the ACKCSC is the primary source for AKC breeders to find out about the health of cavaliers. The ACKCSC has refused to accept that responsibility, and instead, it has misled the AKC breeders about the true MVD breeding protocol in the United States.

CKCSC,USA Up-Side-DownIn April 2010, the Cavalier King Charles Spaniel Club, USA (CKCSC,USA) withdrew its 1998 endorsement of the MVD Breeding Protocol and replaced it with a recommended guideline even more worthless than that of the ACKCSC. The CKCSC,USA's new guideline is:

"The CKCSC,USA recommends that prior to breeding any Cavalier, the dog have 1) a clear rating at two years of age from an auscultation by a board certified veterinary cardiologist; ..."

This new worthless guideline ignores the research experts' conclusions that: (A) All four parents of the breeding pair be MVD-clear as of their 5th birthday; (B) The breeding pair be at least 30 months old and MVD-clear at the time of breeding; and (C) No cavalier be bred if diagnosed with an MVD murmur before its fifth birthday.

In October 2010, in the face of an onslaught of justifiable criticism, the board tweaked their bogus breeding recommendation thusly:

"The CKCSC,USA recommends that prior to breeding any Cavalier, the dog should have a heart clearance from an auscultation by a board certified veterinary cardiologist that is consistent with prevailing cardiology protocols; however, the CKCSC,USA recommends a minimum of a cardiology clearance at age 2.5 years by a board certified cardiologist."

So we find that the two CKCS breed clubs in the United States are not a part of the solution to early-onset mitral valve disease in the breed.  Instead, these clubs are affirmatively contributing to the problem by enabling breeders to ignore the protocol and continue to breed generations of cavaliers destined to develop early-onset MVD.

By shunning the real MVD Protocol and actually increasing the breedings of cavalier King Charles spaniels in violation of the MVD Protocol, the large majority of American breeders have acted in callous disregard for the health and welfare of future generations of cavaliers. They continue to breed untested, un-cleared, and/or under-aged cavalier King Charles spaniels in the United States, and the number of breedings and resulting litters of these early death-marked cavaliers has increased dramatically since the American breeders were warned by the experts in 1998 to stop breeding underaged cavaliers and never breed any cavalier in violation of the MVD Protocol.

Similarly, in the United Kingdom, the chairman of its Cavalier King Charles Spaniel Club stated in March 2009:

"There are many members who are still not prepared to health check their breeding stock, and of those who do, it would appear that many would not hesitate to breed from affected animals."

In 2010, 55% of all cavalier litters registered with the UK Kennel Club had at least one parent under the age of 2.5 years.

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Research News

Swedish Cavalier ClubMay 2013: Sweden's cavaliers show great progress against MVD in 2012. The Swedish Kennel Club reports that of 988 cavaliers tested in 2012 for mitral valve disease, only six under the age of four years had murmurs, and only 61 of all of them had murmurs. The Swedish Kennel Club and the Swedish Cavalier Club follow a mandatory modified version of the MVD breeding protocol. See its breeding protocol here.

The Swedish clubs do not require that all stethoscopic examinations of the cavaliers' hearts be performed by veterinary cardiologists, which is a requirement of the MVD Breeding Protocol. However, all Swedish veterinarians who are licensed to issue clear-heart certfiicates for this registry must pass an auscultation examination conducted by Sweden's top cardiologists/researchers, Professors Clarence Kvart and Jens Häggström.

2011: Dutch CKCS club implements mandatory MVD breeding tests. The Dutch cavalier King Charles spaniel club (Cavalier Club Nederland) and the Dutch Kennel club has implemented a mandatory modified version of the MVD breeding protocol. In theirs, all breeding stock cavaliers must have their hearts examined by ultrasound at age one year or prior to breeding. Thereafter, their hearts must be re-examined by auscultation by a specialist. If a mitral valve murmur is detected before the dog's fifth birthday, it may not be bred.

2011: Canada's CKCS club endorses MVD Breeding Protocol. The Canadian cavalier club has Cavalier King Charles Spaniel Club of Canadaendorsed the MVD breeding protocol. On its website, it states:

"The Cavalier King Charles Spaniel Club Of Canada has recently included the recommendation within its Breeders' Guidelines that Breeders breed Cavalier King Charles Spaniels that are at least 2.5 years old and murmur-free that have parents that were murmur-free at age 5 years."

However, the Canadian club's version of the MVD Breeding Protocol does not require that veterinary cardiologists perform the stethoscopic examinations for heart murmurs.

January 2011: UK CKCS breeders still largely ignore the MVD Breeding Protocol. In 2010, 55% of all cavalier litters registered with the UK Kennel Club had at least one parent under the age of 2.5 years.

October 2010: CKCSC,USA modifies its new phony MVD breeding protocol. In April 2010, the CKCSC,USA's board of directors replaced the REAL protocol with a worthless watered-down version, in which they stated:

"The CKCSC,USA recommends that prior to breeding any Cavalier, the dog have a clear rating at two years of age from an auscultation by a board certified veterinary cardiologist."

In the face of an onslaught of justifiable criticism, the board met in October and tweaked their bogus breeding recommendation thusly:

"The CKCSC,USA recommends that prior to breeding any Cavalier, the dog should have a heart clearance from an auscultation by a board certified veterinary cardiologist that is consistent with prevailing cardiology protocols; however, the CKCSC,USA recommends a minimum of a cardiology clearance at age 2.5 years by a board certified cardiologist."

This October revision is only a miniscule improvement over their April version and is still worthless. It ignores these essential elements of the REAL protocol:

• Do not breed any cavalier under the age of 5 years, unless its parents' hearts were free of MVD murmurs by age 5 years.

• Do not breed any cavalier who is diagnosed with an MVD murmur under the age of 5 years.

September 2010: Swedish Kennel Club's modified mandatory MVD breeding protocol is not showing progress. In a 2010 study by cardiologist Dr. Clarence Kvart of the mandatory Swedish CKCS club breeding protocol -- which is weaker than the MVD protocol recommended by Lennart Swenson -- Dr. Kvart reports that that the prevalence of MVD in six-year-old cavalier King Charles spaniels, born 2001 and 2003, is at least 50% and lacks signs of decrease despite the current breeding program introduced in Sweden 2001. The Swedish clubs have declined to toughen their program to match Prof. Swenson's recommendation.

CKCSC,USAApril 2010: CKCSC,USA dumps MVD Breeding Protocol. The Cavalier King Charles Spaniel Club, USA (CKCSC,USA) has withdrawn its 1998 endorsement of the MVD Breeding Protocol and replaced it with a recommended guideline even more worthless than that of the ACKCSC. The CKCSC,USA's new guideline is:

"The CKCSC,USA recommends that prior to breeding any Cavalier, the dog have 1) a clear rating at two years of age from an auscultation by a board certified veterinary cardiologist; ..."

This new worthless guideline ignores the research experts' conclusions that: (A) All four parents of the breeding pair be MVD-clear as of their 5th birthday; (B) The breeding pair be at least 30 months old and MVD-clear at the time of breeding; and (C) No cavalier be bred if diagnosed with an MVD murmur before its fifth birthday.

2010: ACKCSC concocts fictitious, worthless MVD breeding guideline. The American Cavalier American Cavalier King Charles Spaniel ClubKing Charles Spaniel Club (ACKCSC), which is the CKCS parent club of the American Kennel Club (AKC) has pointedly ignored the MVD breeding protocol and has gone so far as to even concoct a fictitious MVD breeding guideline of its own. On its website, the ACKCSC has stated:

"Currently, the recommended practice is to wait until a Cavalier is two years old or older before the first breeding and to know the parents and ancestral cardiac status. Cavaliers with early onset presentations of MVD (before four years of age) should not be bred and breeders need to work with the guidance of their cardiologists."

Instead of not breeding until age 2.5 years, ACKCSC claims in its baseless "recommended practice" to start breeding at 24 months, and it also shortens the definition of early-onset MVD from five years to four years. Instead of requiring that all four parents of the breeding pair be certified to be murmur-free by age five years, ACKCSC says its "recommended practice" is simply "to know the parents and ancestral cardiac status." That is a meaningless phrase apparently designed to provide AKC breeders with "cover" for ignoring the real MVD breeding protocol. It allows them to claim that, in their "wisdom" as experienced breeders, they "know the parents" and they have taken into account the "ancestral cardiac status".

The ACKCSC, as the AKC's parent club for cavaliers, has been assigned by AKC the responsibility of "the education of breed owners on the nuances of the breed, and overseeing the breed's health and welfare." So, the ACKCSC is the primary source for AKC breeders to find out about the health of cavaliers. The ACKCSC has refused to accept that responsibility, and instead, it has misled the AKC breeders about the true MVD breeding protocol in the United States.

March 2009: UK's cavalier club chairman says many club breeders ignore health checks. Mrs. Lesley Jupp, Chairman of the Cavalier King Charles Spaniel Club of the UK, stated on March 24, 2009:

"There are many members who are still not prepared to health check their breeding stock, and of those who do, it would appear that many would not hesitate to breed from affected animals."
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Related Links

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Veterinary Resources

Mitral Valve Disease in Cavalier King Charles Spaniels. Darke, P., Fuentes VL, Kvart C, Häggström J. Swenson L.  Proceedings, Seminar by Intervet UK Ltd and The Cavalier King Charles Spaniel Club UK. November 1996.

International Symposium on Chronic Cardiac Valve Disease in the Cavalier King Charles Spaniel. Beardow A, Buchanan J, Fuentes VL, Keene B, Swenson L. Transcript of Private Recording of Proceedings, CKCSC,USA. May 1998.

Evaluation of the Swedish breeding program for cavalier King Charles spaniels. Tobias Lundin, Clarence Kvart. Acta Veterinaria Scandinavica, Sept. 2010, 52:54. Quote: "The Swedish Kennel club and the Special club for cavalier King Charles spaniels (SCKCS) started a breeding program in 2001 with the aim of reducing MMVD in the Swedish population of CKCS. In this program, dogs are not allowed to breed until four years of age and need a heart auscultation without murmurs within eight months before mating. However, dogs are allowed to breed at an age of 24 months, if the dog and its parents are examined and no murmurs are detected. Male dogs that have a heart auscultation at seven years of age without murmurs are allowed to breed without further heart evaluation. Breeding animals whose parents have heart murmurs before four years of age are not allowed to breed. The aim of this investigation was to study the prevalence of heart murmurs in the Swedish population of six-year-old CKCS born 2001 and 2003, and to estimate if prevalence has decreased since the breeding program was introduced 2001. ... In this investigation 353 CKCS were selected as a sample of the population and 150 were examined by auscultation for heart murmurs when they reached the age of six years in 2007 and 2009. ... The effect of the breeding program was evaluated by comparing the prevalence of heart murmurs in the two groups. In 2007, the prevalence of heart murmurs was 52% (50% for females and 54% for males) and in 2009, the prevalence was 55% (44% for females and 67% for males). No significant difference was found in the prevalence of heart murmurs between 2007 and 2009 (P=0.8). For all six-year-old CKCS, the prevalence of heart murmur was 53% (females 46% and males 61%), which is higher than previous Swedish investigations. ... The result from this investigation indicates that the prevalence of MMVD in six-year-old cavalier King Charles spaniels, born 2001 and 2003, is at least 50% and lacks signs of decrease despite the current breeding program introduced in Sweden 2001."

Heritability of premature mitral valve disease in Cavalier King Charles spaniels. Tom Lewis, Simon Swift, John A. Woolliams, and Sarah Blott. Vet J, April 2011, 188(1):73-76. Quote: "Mixed model analysis of 1252 records of cardiac auscultation of ≥4- to <5-year-old Cavalier King Charles spaniels (CKCS) from 1991 to 2008 in conjunction with the Kennel Club pedigree records of all dogs registered from the mid 1980s to September 2007 was used to estimate variance parameters of premature mitral valve disease (MVD). Data were limited to dogs 4 and <5 years of age to ensure diagnostic distinction between early and late onset MVD. Cardiac murmurs were detected in 108/1252 (8.6%) dogs. Heritability estimates of 0.67 (standard error, SE 0.071) for the grade of murmur and 0.33 (SE 0.072) for the presence/absence of murmur were calculated. The variance due to clinician was 0.02 (SE 0.012) for grade and 0.03 (SE 0.017) for presence/absence of murmur. These results indicate that the presence and severity of MVD, as assessed by cardiac auscultation, in 4- to 5-year-old CKCS is highly heritable and that selection against the disease should be successful."

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