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We are grateful to Anne Marie Rasmussen from Canada who has written about :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 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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