Mitral Valve Disease (MVD) or Endocardiosis (as referred to by veterinarians) is a chronic degenerative heart disease affecting the valve between the left atrium and the left ventricle. Deposition of mucopolysaccharide in the valve and its attached cords causes the valve to become distorted and allows blood to leak back into the atrium during contraction of the ventricle. Most often only the mitral valve is affected, but in one-third of affected dogs, the tricuspid valve (between the right atrium and the right ventricle) is affected as well. MVD is most often seen in small breeds, particularly the Cavalier King Charles Spaniels and most other small spaniels. The Chihuahua, Miniature Poodle, Miniature Pinscher, Dachshund, Pekinese and Whippet can be affected as well.
A diagnosis of MVD is usually done by auscultation. Murmurs are rated as grade 1 through 6 and is dependent on how loud the heart murmur is. As MVD progresses, your dog’s heart murmur will be become louder; to the point that you’ll be able to hear the murmur without a stethoscope. As the heart disease progresses, other organ systems can be affected. Controversy remains about when to start treatment for MVD. Commonly, treatment begins at stage 3.
The most common treatments include a vasodilator such as enalapril, a diuretic such as furosemide and digoxin, a drug to help the heart beat slower and stronger. Surgical mitral valve replacements have been successful, but this is not considered standard treatment yet. A yearly heart exam is strongly recommended.
There is a strong genetic component for contracting MVD. Breeders are encouraged to use older stud dogs (over 5 years old) with healthy hearts. Another suggestion asks that Cavaliers be at least 2 to 2 and a half years old and free of heart murmurs when breeding.