Mitral Valve Disease (MVD) is the most common form of heart disease that develops in dogs. It generally occurs in small to medium size dogs rather than big dogs.
There seems to be a genetic tendency to the development of MVD in certain breeds, which include: Cavalier King Charles Spaniels, Poodles, Schnauzers, Chihuahuas, Fox Terriers and Boston Terriers.
Male dogs are more commonly affected than females and it is mostly older dogs who tend to show signs of this disease, although young dogs can be affected too. MVD is a disease affecting the surface of the heart valves. Other terms you may hear used to describe MVD are endocardiosis or valvular insufficiency.
In MVD, one of the heart valves gradually becomes thickened, lumpy, distorted and leaky, so that when the ventricle pumps, some of the blood flows backwards into the atrium. This backward flow creates a noise that your vet can hear with a stethoscope, and is called a murmur. Vets often grade a murmur depending on how loud they are compared to the normal sounds when the heart beats.
This leaking means that the heart is working less efficiently and as MVD progresses your dog will start becoming unwell and will show signs of heart failure.