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| Mitral Valve Disease
(MVD) |
This disease is a condition which eventually affects most Cavalier King Charles Spaniels worldwide to some degree. In some cases it may shorten the lifespan of the Cavalier, though some may live past the average lifespan for the breed despite having symptoms of MVD. Mode of Inheritance: unknown, most likely polygenic 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, 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 diseases 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. Symptoms 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 who 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 hear) 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. Treatment Treatment will depend upon the grade of the 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 hear 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 breath 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 coughing and laboured breathing medications such as vasodilators and diuretics will be considered. Implication for Owner The Cavalier will have their heart checked during their annual visit to the veterinarian for a heart murmur. Many Cavaliers do develop a murmur which is the early sign of MVD, however, if the progression of the disease is slow, they may live out long lives without further symptoms or requiring medications. In many cases, a Cavalier will not need heart medications or monitoring until late in life. Implication for breeders At present the mode of inheritance is unknown for MVD, though it is suspected to be polygenetic (several genes involved) and multifactorial (environment, food, weight). 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. At the moment the most commonly used test available to breeders is annual auscultation (listening to the heart with a stethescope) by either a veterinarian or preferably a cardiologist. (Please note: cardiologists are not always available to breeders in all areas of every country, so some breeders may have no choice but to use a veterinarian which is acceptable). One problem with this test is that it only tells a breeder that at the time the test was performed the dog did not have a heart murmur. This does not mean that the dog will not develop MVD at any point in time nor does it mean that the dog does not carry the genes which might produce MVD. Only a definitive test like DNA which is not available with respect to MVD would be able to tell if a dog was clear of MVD. Dr. Rusbridge in the UK has undertaken a DNA study which includes Syringomylia, Mitral Valve Disease and Epilepsy. Information on this study can be found at the Cavalier King Charles Spaniel Club, UK site at http://www.thecavalierclub.co.uk/ Another important factor in Mitral Valve Disease is the rate of progression of the heart murmur and this is why breeders should continue to monitor the heart on an annual basis to see how fast the progression of the degeneration of the valve which is indicated by the grade of murmur. The realities are that likely all Cavaliers alive carry the genes for MVD, given their breed history, so it is extremely doubtful that 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. By having their dogs checked annually for evidence of a heart murmur and breeding older, mature dogs who are unaffected it is hoped that the age of onset will also move back as well, which may be the best that can be hoped for in the breed |
