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Mitral Valve
Disease
What is Mitral Valve Disease
(MVD)?
The heart consists of 4 chambers, 2 atria and 2 ventricles,
with the atrioventricular valves ensuring that blood flows from the atria to
the ventricles when the heart is beating. A defect or weakness in the mitral
valve or the left atrioventricular valve allows some blood to move back into
the left atrium, known as mitral regurgitation. This means the heart is less
efficient at pumping blood through the body.
Mitral valve insuffiency is the
most common of the acquired cardiac disesase in older dogs, affecting over 1/3
of dogs older than 10 years. However, in certain breeds, mitral valve
insufficiency develops at a younger age, due to an inherited predisposition for
the disorder.
Some of the breeds affected with a higher incidence of this
condition are the Cavalier King Charles Spaniel, Cairn Terrier, all 3 sizes of
Poodles, Bull Terrier, Miniature Pinschers, Whippets, Chihuahua, Pekinese,
Dachshund, Beagle, Papillion, Dobermans, Great Dane and German Shepherd. In
general, the smaller breeds are most often affected.
What does it really mean?
The first signal that a dog might have Mitral Valve Disease
is the development of a heart murmur. However, a dog with a heart murmur may
live a full life span, depending upon the progression of the disease in that
particular dog. Some dogs who have developed heart murmurs at young ages have
lived to the average lifespan of that breed. A veterinary while listening to a
dog's heart may hear a heart murmur on the left side. (Please note there are
other causes for heart murmurs, to diagnose MVD it will depend upon where the
regurgitation is heard) The veterinary will then grade the murmur for severity
from Grade 1 (mild) to Grade 6 (severe) and depending upon the grade will
advise proper treatment.
Treatment
Treatment will depend upon the grade of murmur and
any clinical signs your dog may be showing.
During the early stages of the
disease, though a systolic murmur of grade 1-2 is heard there are usually no
clinical signs. As the disease progresses, the murmur will become more audible,
the dog may become intolerant of exercise, respiratory rate will increase and
finally as fluid begins to accumulate in the lungs coughing and laboured
breathing develops.
Many dogs live for years with a low grade murmur and
treatment consists of dietary changes such as low sodium foods. Some Cavalier
King Charles Spaniel breeders are recommending that any dog diagnosed with a
heart murmur is put on Co-enzyme Q10. This is a natural medication which may be
helpful in treating the disease. While no studies have been done with this
medication in dogs, there have been considerable studies in humans and the
evidence is pointing to great success in treatment of cardiac disease with its
use. Co-enzyme Q10 is an over the counter product and can be picked up at
virtually any drug store or health food store.
As the disease progresses and
clinical signs appear such as the coughing and laboured breathing medications
such as vasodilators and diuretics will be considered.
What is testing all about?
At present the mode of inheritance for Mitral Valve Disease
in Cavaliers in unknown. It is considered multi-factorial. In other words there
is a genetic predisposition for the disease but other unknown factors will go
into why one dog is affected and at what age and another dog, even a
littermate, is not affected at all.
While it is extremely doubtful the disease will
ever be irradicated from the Cavalier King Charles Spaniel completely, the hope
of breeders is to move the age of onset back as late in life as possible. So
many breeders will have their dogs checked annually for evidence of a heart
murmur and breed mature dogs who are unaffected. By breeding older Cavaliers
who are clear of a murmur until as late as possible in life it is hoped that
the age of onset will also move back as well.
The suggested protocol at present
in many countries is to try to breed females who are older than 2 years of age
and clear, to males who are 6 years and older and still clear. As yet there is
no evidence that this protocol is successful but it is still early days yet.
Testing is merely a breeder's tool to try to establish a
dog's health at any point in time. It does not mean that dog may not develop a
heart murmur 3 months onwards or that he will not produce puppies with Mitral
Valve Disease. Also while testing is important in Cavaliers one should also ask
one's breeder about the lifespan of their dogs. Longevity is the true test.
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on this site is copyrighted by Rhiannon Cavalier King Charles Spaniels and
Creature Comforts Inn. Redistribution on any other website is only
permitted via a link to this site.
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