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Category: Canine
Chronic degenerative atrioventricular valvular disease, endocardiosis, chronic valvular fibrosis
Mitral valve disease, mitral valve degeneration, mitral valve insufficiency
AffectedAnimals:
Dogs. The disease is extremely rare in cats. Mitral valve disease more commonly affects middle-aged and older small-to-medium sized breeds. Breeds with a high prevalence of this disease include the cavalier King Charles spaniel, the Chihuahua, the miniature poodle, the miniature pinscher, fox terriers, Boston terriers, and miniature schnauzers. Males are 50 percent more likely than females to be affected. Cavalier King Charles spaniels may have symptoms at an earlier age than other breeds.
Overview:
Mitral valve disease is a serious heart condition caused by the abnormal function of the valve that separates the upper and lower chamber of the left side of the heart. Dogs with mitral valve disease typically have difficulty exercising and a cough that increases in frequency as the disease progresses towards congestive heart failure and pulmonary edema.
The heart is made up of four chambers: the left and the right atria and left and right ventricles. Each upper chamber, or atrium, is separated from a lower chamber, or ventricle, by an atrioventricular valve. The valve on the left side of the heart is called the mitral valve, and the valve on the right side is called the tricuspid valve. In a normal dog, the leaflets of each valve open to allow blood to move from the atria into the ventricles and then close completely when the heart pumps the blood out of the ventricles and into the blood vessels.
Right Atrium
Right Atrioventricular Valve (Tricuspid Valve)
Right Ventricle
Left Atrium
Left Atrioventricular Valve (Mitral Valve)
Left Ventricle
Papillary Muscle
Chordae Tendinae
Diseased Mitral Valve Leaflets
Mitral valve disease is caused by the accumulation of the plaque within the heart valve, although the cause of this plaque is unknown. The plaque results in the deformation of the valve leaflets and regurgitation of blood back into the atrium. This leakage in turn causes a decrease in blood flow from the heart. A valve that fails to close completely will allow blood to leak back into the atrium, resulting in a heart murmur.
In order to compensate for this deficiency, the heart dilates and the volume of blood pumped increases. This compensation allows a dog to remain free of symptoms for some time, but simultaneously worsens the disease, the eventual result of which is congestive heart failure.
Mitral valve disease is more common in middle-aged and older small-to-medium breeds. While the prognosis for dogs with mitral valve disease is poor, some dogs may be managed with medications for a period that varies from case to case. Dogs may live for years after manifesting symptoms of mitral valve disease.
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