Degenerative mitral valve disease (DMVD) is a common acquired heart disease of older dogs that is characterized by progressive degeneration of the mitral valve on the left side of the heart, which causes the valve to leak (mitral regurgitation). Over time, if the leak is severe enough, the chambers of the left side of the heart (the left atrium and the left ventricle) enlarge. Pressure may then back up into the blood vessels in the lungs, allowing fluid to seep out of the vessels and into the air spaces of the lungs (pulmonary edema). When an animal has evidence of fluid in the lungs secondary to heart disease, this is called congestive heart failure. Other potential complications of DMVD include arrhythmia (abnormal heart rhythm), syncope (“fainting”), pulmonary hypertension (resistance to blood flowing to the lungs), and decreased contractility of the heart.
Treatment of DMVD generally involves attempting to slow disease progression with medications, as well as managing clinical signs when they arise. Ultimately the goal is to provide your pet with the best quality of life for as long as possible. Unfortunately, definitive treatment options (such as surgical mitral valve repair or replacement) are limited in veterinary patients.
The prognosis for mild DMVD is good, and most dogs remain free of clinical signs associated with mild disease for several years. The short-term prognosis for more advanced degenerative mitral valve disease is generally fair with appropriate therapy and monitoring; the long-term prognosis at this stage of disease is dependent on how quickly it progresses. Once a dog has developed congestive heart failure secondary to DMVD, reported median survival times for small to medium breed dogs range from 6-18 months after the first episode of heart failure. However, an individual animal’s prognosis is dependent on several factors, such as concurrent arrhythmia, pulmonary hypertension or decreased left ventricular contractility, as well as the presence of other diseases like chronic kidney disease. Unfortunately, DMVD in larger breed dogs tends to progress more rapidly than small and medium breeds, and larger breed dogs seem to be at higher risk for the development or arrhythmia and decreased left ventricular contractility.
Echo video loops showing a thickened, irregular mitral valve (characteristic of degenerative mitral valve disease) with significant enlargement of the left side of the heart (left); color flow Doppler showing a severe leak (regurgitation) at the mitral valve (right)