Cardiac & Circulatory
A primary health concern for Cavalier King Charles Spaniels is a form of degenerative valve disease called Mitral Valve Disease (MVD). Through careful breeding programs breeders have been successful in delaying the onset of this disease, but it will take many more years of careful breeding.
What is Mitral Valve Disease (MVD)?
The heart consists of 4 chambers, 2 atria and 2 ventricles, with the atrioventricular valves ensuring the blood flows from the atria to the ventricles when the heart is beating. A defect or weakness in the mitral valve, or left atrioventricular valve, allows some blood to move back into the left atrium. This is known as mitral regurgitation. Mitral valve insufficiency is the most common of the acquired cardiac diseases in older dogs, affecting over 1/3 of dogs older than 10 years. However, in certain breeds including the Cavalier King Charles Spaniel, mitral valve insufficiency develops at a younger age, due to an inherited predisposition for the disorder.
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 up the progression of the disease in that particular dog. Some dogs that have developed heart murmurs at young ages have lived to the average lifespan of that breed. A veterinarian, 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 veterinarian will then grade the murmur for severity from Grade 1 (mild) to Grade 6 (severe) and depending upon the grade will advise proper treatment. Severe Mitral Valve Disease will eventually lead to Congestive Heart Failure.
Implication for Owner
The Cavalier will have their heart checked during his or her annual visit to the veterinarian. Cavaliers that develop murmurs might have early signs of MVD. If the disease is present and progresses, the murmur will become more audible, the dog may become intolerant of exercise, respiratory rate will increase, fluid will begin to accumulate in the lungs and the dog will develop coughing and labored breathing. In most cases, a Cavalier will not need heart medications until late in life. There are treatments available to assist with management of advancing MVD. A board Certified Veterinary Cardiologist should be consulted to determine the exact mode of therapy for each Cavalier.
Implication for breeders
At present, MVD inheritance in the Cavalier is speculated in the veterinary community, however, research funded by the ACKCSC Charitable Trust is ongoing to confirm this hypothesis. The inheritance is suspected to be polygenetic (several genes involved) with multifactorial influences (e.g., dog's environment, food and weight). In other words, there would be a genetic predisposition for the disease but other factors will come into play similar to other species (such as humans). The Cavalier King Charles Spaniel has been studied and screened for over 20 years thanks to the dedication and generosity of owners, breeders and cardiologists in the USA. To date, other purebreds and mixed breed dogs predisposed to MVD have not been studied and screened to the level of Cavaliers.
The recommended health screenings for Cavaliers are annual auscultations (listening to the heart with a stethoscope) by board certified cardiologists and doppler (Echocardiogram) if there is a question on auscultation. The ACKCSC, Regional Cavalier clubs and local AKC All Breed Clubs are hosting and making health clinics with cardiologists accessible to breeders and owners throughout the USA. 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.
Screening for MVD
By having Cavaliers screened annually by board certified cardiologists for evidence of heart murmurs and breeding unaffected older dogs, breeders are striving to move the age of onset of the disease as far as possible. Some Cavaliers have not presented with cardiac disease even at advanced ages. An important factor in Mitral Valve Disease is the rate of progression of the disease (if present) and this is why breeders and owners are recommended to continue to monitor their Cavalier's heart on an annual basis. In reality though, cardiac diseases cannot be totally eradicated in dogs or humans.
In closing, we must understand that this is a greater canine (mixed breeds & purebred) health issue. "Degenerative valve disease accounts for about 75% of cardiovascular disease in dogs. Approximately 60% of affected dogs have degeneration of the mitral valve, 30% have lesions in both the tricuspid and mitral valve leaflets, and 10% have only tricuspid valve disease. In dogs, the disease is age and breed related, with older, small-breed dogs demonstrating a higher incidence. There is also a slight predisposition among male dogs". Quote Source: Degenerative Valve Disease by: Dr. Robert Prosek.