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Mitral valve disease is a condition where, over time, the mitral valve of the heart degrades. The heart is separated into 4 chambers; top and bottom, left and right. The upper chambers are the atria (singular atrium) and the lower chambers are the ventricles. There are valves which are in place between each of the chambers to keep blood flowing in one direction. Blood travels from the right atrium to the right ventricle into the lungs, where it is oxygenated, then into the left atrium and finally to the left ventricle and out to the rest of the body. The mitral valve is located between the left atrium and the left ventricle. It functions here to prevent the back flow of blood back into the left atrium. When functioning correctly all the blood contained in the left ventricle will be pumped out into the body as the heart contracts. As the mitral valve degrades it cannot close properly and small amounts of blood leak back into the left atrium. The condition is progressive and over time the valve will continue to degrade until the heart can no longer compensate. The result of this is that the heart must work harder to supply blood to the body. This eventually leads to congestive heart failure. Mitral valve disease is seen most often in older small dogs.
MVD is common in older, small dogs. There are however, certain breeds which seem to be at a higher risk for developing this disease. These breeds include the Cavalier King Charles Spaniel, Norfolk Terrier, and Japanese Chin. Of these breeds the Cavalier King Charles Spaniel is at the highest risk of developing MVD and it is suggested that, beginning at age one, all Cavaliers should be checked for heart problems.
The exact cause for mitral valve disease is not known. In some breeds however there is very strong evidence that it is genetic. One of these breeds is the Cavalier King Charles Spaniel. There has been and currently is research going on to find out more about this disease.
The first sign that your dog may have mitral valve disease is a heart murmur. This can normally only be heard by using a stethoscope. Because of this it is important to take your dog to the veterinarian every year for a checkup. In the early stages of MVD a heart murmur may be the only sign and dogs will still act happy and healthy. As the disease progresses the hear murmur will get worse and other symptoms will arise. These symptoms are normally ones which are associated with congestive heart failure. They include a cough, increased blood pressure, lethargy, reluctance to exercise, and in some cases fainting. Treatment options will depend on how much the disease has progressed.
There are a number of ways in which mitral valve disease can be diagnosed. The first is auscultation, or listening with a stethoscope. By listening to the heart a veterinarian can hear heart imperfections such as heart murmurs and arrhythmias. It is also possible for them to hear lung sounds to determine the overall progression of the disease. A second method is a chest radiograph. A chest x-ray can show the size and shape of the heart. An enlarged heart is a sign that it is not functioning properly. An electrocardiogram (ECG) can also be used in the diagnosis of MVD. The ECG provides information about the electrical activity of the heart. A final method used to diagnose MVD is an ultrasound. An ultrasound of the heart is called an echocardiogram. When doing an echocardiogram a veterinarian can see, in real time, the activity of the heart. In dogs that have MVD the flow of blood can be seen as it is regurgitated back into the left atrium. All of these methods can help diagnose and track the progression of mitral valve disease.
There is currently no cure for mitral valve disease. The option of replacing the degenerate valve is available but is very expensive and requires the dog to be healthy enough to undergo surgery. The usual treatment option is to manage the heart failure. This is done by using medications which help improve heart function. These include diuretics, which help remove excess water from the body, digitalis, which strengthens the contractions of the heart, and vasodilators, which make it easier for blood to flow through out the body. In addition to these a diet low in sodium may be prescribed by your veterinarian. The goal of treatment is to improve the dog's quality and length of life.
As with any disease it is very important to follow your veterinarian's instructions when caring for your pet with MVD. All medications should be giving at the specified times and in the right dosage. To make your dog more comfortable their activity may need to be restricted along with keeping them at a healthy weight; not too heavy and not too thin. If you notice any changes in your dog's behavior it should be noted and reported to your veterinarian.
The AKC Canine Health Foundation has funded 9 grants dealing with mitral valve disease. There are 3 active grants that are currently being funded which deal with slowing the progression of the disease and looking into factors which cause the disease. With your help we can continue to look for better treatment options and ways to prevent this disease.
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