(by C Alport; content approved by Dr RW Mitten BVSc DVM)
As a breed, Cavalier King Charles Spaniels are genetically predisposed to a heart condition known as Mitral Valve Disease. In most breeds and in humans, degeneration of the Mitral Valve is a normal aging condition, but the onset of the condition in Cavaliers can occur at much younger ages than in other animals. This "early onset MVD" is genetically inherited, and generally leads to a shortened lifespan. Through early diagnosis however, affected breeding dogs/bitches can be removed from breeding programs and they and affected pets can undergo lifestyle changes which will improve their chances of combating the symptoms of the condition.
Mitral Valve Disease is the commonly used term to describe premature aging and degeneration of the Mitral Valve, in the heart. The Mitral Valve is supposed to allow blood to flow from the left atrium into the left ventricle but not vice versa, as it makes its way around the heart before being sent back into the body. As a result of Mitral Valve degeneration, blood flows back into the left atrium, placing strain on this chamber of the heart and ultimately leading to congestive heart failure. This "backflow" is known as Mitral Regurgitation or Mitral Valve Insufficiency and is diagnosed initially by the sound of a systolic murmur. Symptoms, as the disease progresses, will include coughing, difficulty in breathing, loss of appetite and unwillingness to exercise. Medication is required in the latter stages, to reduce fluid build-up in the lungs, stabilise the heart and improve quality of life for the dog. Less commonly, the same type of degeneration can affect the Tricuspid and Aortic valves.
The art of listening to heart sounds is known as "auscultation" and this is how Mitral Valve Disease is (generally) initially diagnosed in dogs, by suitably qualified veterinarians. When a dog is free of a murmur, it is pronounced "Heart Clear" but when a murmur is found, the murmur is graded from I (mild, no symptoms) to VI (severe, latter stages of congestive heart failure). According to studies, most GP vets cannot detect a murmur until it reaches Grade III or IV, by which time a breeding dog/bitch may have produced the problem in a number of offspring. By allowing a specialist in auscultation to listen to your dog's heart, you greatly improve the chances of an early diagnosis of MVD. If your dog/bitch is being bred from, and is found to have MVD, you can remove it from your breeding program, thus decreasing the number of offspring affected (and bred from). Whether or not your dog is bred from, an early diagnosis will allow you to make lifestyle choices which will improve your dog's quality of life: changing their diet to exclude salt; adjusting their exercise regime as appropriate; weight loss if required and administering medication.
On the positive side, if your dog is pronounced "Heart Clear" and is over five years of age, it is more likely to live over 10 years of age, and it’s breeding may be quite important for breeders to pursue (assuming the dog is free of other hereditary problems). Even if your dog has been desexed, the breeder may have littermates and other near relatives still being bred from, so the breeder of your dog may be grateful for the information you can provide.
For further information about MVD in Cavaliers, the following websites contain a lot of helpful information:
Australian Clear Hearts Register: www.geocities.com/ozcavaliers3/index.htm
Premier Cavalier info site: www.premiercavaliersite.net/MVD.htm
Cavalier Club (UK): www.cavalierclub.co.uk/breed/mvd2000/
Helping He@rts - About MVD: http://cavalierkingcharles.com/Helping_Hearts/MVD.shtml