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Mitral Valve Disease (MVD)

Perhaps one of the most heartbreaking aspects of owning a Cavalier King Charles Spaniel is the knowledge of that ever-looming timeline: That somewhere between the age of 8 - 10 years old (and unfortunately sometimes even earlier, despite even the most reputable breeder efforts), we can expect to hear what are probably the most commonly stated and regretted words uttered from the mouths of  veterinarians and cardiologists to Cavalier owners everywhere....

 "Your Cavalier has a heart murmur."

 

A heart murmur adds an extra sound to a heartbeat — introducing a whooshing noise that your veterinarian and cardiologist can hear when they listen to your dog's heart. A murmur can be mild and barely detectable (grade 1-2), or quite loud (grade 3 - 6), and possibly even strong enough that it can be felt placing a hand on your dog's chest.

Murmurs are graded 1 to 6 :

Grade 1 – Barely audible

Grade 2 – Can consistently be heard with a stethoscope

Grade 3 – Can be heard as soon as the stethoscope is applied

Grade 4 – Very audible barely touching chest (murmur can be felt with hand)

Grade 5 – Very loud, audible without stethoscope

Grade 6 – So loud it can be heard without a stethoscope

Mitral Valve Disease (MVD) is a degeneration of the heart's mitral valve, which is one of four sets of valves in a dog's heart. A dog's heart valves have flaps (leaflets) which open and close tens of thousands of times a day. This is what forces blood flow through the heart.  The valves open and blood flows forward. They close and this prevents blood from going backward.  This all-important valve--the mitral valve--is located between the left atrium and ventricle.

drawing of the heart and mitral valve

Figure 1

After developing a murmur (but usually not until grade 3), beginning treatment will be based on whether your Cavalier has an enlarged heart or not. This can be assessed through an x-ray with your regular veterinarian (this step does not require a cardiologist) to determine if the heart has changed in size. With no enlargement, the usual recommendation is to do nothing but follow up with a cardiologist in 6 months, and another x-ray within 6 months to a year. Once heart enlargement is involved, the next step is to begin treating with medication.

 

The most common drug for this is  Pimobendan, which goes by the brand name: Vetmedin® It helps increase muscle strength and lower pressure in the arteries and veins. This medication can extend a dog's life up to an additional 6 - 24 months from the time of involved heart enlargement. Unfortunately, there just is no more specific time frame for how long a dog can live with an enlarged heart. Though true that MVD can follow a typical ordered progression, ultimately it all factors on the level of aggressiveness of the disease in each individual case.

Once the mitral valve is affected, the valve no longer fully closes, and as it continues to degenerate, with continually increasing backflow and stress on the heart, it will eventually bring a dog into heart failure.

When a dog is in heart failure (HF) the heart is still working, but it cannot keep up with the body's need of blood. The symptoms of heart failure can include high respiratory rates, the inability to tolerate exercise, and shortness of breath, to where the effort can even lead to fainting.  This level is then referred to as "congestive heart failure". This leads to pulmonary edema (the buildup of fluid in the lungs) and around the heart, putting pressure on the heart. 

Though scientifically isolating a single gene has proven difficult, top cardiologists in the country and overseas continue to work ever-diligently toward this goal. There is currently a (2023) study being conducted in the United States by Dr. Kate Meurs, at NC State University College of Veterinary Medicine. "The goal of the study is to use the research to develop a test to help breeders decrease the frequency of the disease with hopes to also help use the research to predict disease severity and response to therapy." You can learn more about this study, and possibly even have your Cavalier participate, here: https://hospital.cvm.ncsu.edu/services/small-animals/genetics/cavalier-king-charles-spaniels-mitral-valve-endocardiosis-study/

 

Unfortunately, MVD afflicts over half of all Cavalier King Charles Spaniels by age 5 years and nearly all Cavaliers by age 10. It is the cause of death in many older dogs in different breeds but only Cavaliers have the early onset type. For this reason, it is highly recommended that Cavaliers be screened yearly for the detection of the presence of a heart murmur, beginning at one year of age. No matter if your Cavalier is a pet or part of a breeding program, this needs to be done.

Breeders who conduct these screenings can publish results on the OFA website in order to make these records public, and the public in turn can look up results by entering a dog's information into the search tool.

 

All active Cavaliers of Fairhaven dams' and studs' results can be found on the OFA website. 

 

NOTE: Screening the heart of breeding Cavaliers DOES NOT GUARANTEE THE HEALTH OF A CAVALIER'S HEART AND CANNOT DETERMINE AT WHICH TIME A MURMUR WILL DEVELOP. See our "HEALTH PAGE" to read, "What Is A Health Guarantee, Really?" It is a "best tool" to help a breeder understand  the health of that particular breeding dog so far, and over time and through generations, helps in the continuous reevaluation of that breeder's breeding lines.  

 

Author: Angela Schuller

Disclaimer: As a breeder who cares deeply for my dogs and puppies I act as responsibly as I can.  The information provided is intended to inform and help to lessen the alarm when MVD becomes a topic with your veterinarian. Ultimately, once a puppy leaves my home relinquished to an owner's care, owners must then take on the responsibility for their decisions. As always, if your pet has an urgent medical concern, please consult your veterinarian. Finally, as your trusted breeder, I am always available to offer support and answer questions. 

SOURCES:

 Cavalier Health Website, https://cavalierhealth.org/mitral_valve_disease.htm

Cornell University Website, https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information/get-jump-heart-murmurs#:~:text=A%20heart%20murmur%20adds%20an,hand%20on%20your%20dog's%20chest 

Cavalier Matters Website, https://www.cavaliermatters.org/unique-hereditary-diseases-index/mvd-heart-disease

"Figure 1"jpg, https://www.rvc.ac.uk/research/animals-in-research/case-studies/mitral-valve-disease-in-dogs   Accessed 22 July 2023

NC State University, College of Veterinary Medicine, https://cvm.ncsu.edu/cavalier-king-charles-spaniels-research/

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