Degenerative mitral valve disease (MVD) - often referred to as myxomatous mitral valve disease (MMVD) - is the most common form of heart disease diagnosed in dogs. Although dogs may live comfortably with the disease, many die due to complications associated with disease progression including congestive heart failure. Dr. Katsuhiro Matsurra - a veterinary heart surgeon - explains the anatomy of the heart and how severe mitral valve disease results in congestive heart failure.