Mitral valve insufficiency is the most common acquired cardiac disease in older dogs, affecting over one third of dogs greater than 10 years of age. In some breeds however, mitral insufficiency develops at a much younger age, due to an inherited predisposition for this disorder. Although the pattern of inheritance has not been identified, it is agreed that there is a genetic basis for the early development of mitral valve disease. It is also seen, not as commonly, in the miniature pinscher, toy and standard poodle, whippet, chihuahua, Pekinese, dachshund, beagle, papillon, great Dane, and German shepherd. In general, small breeds are most often affected.
Some studies show a greater incidence in males than in females.
For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a general consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed. You can help by maintaining your dog at a healthy weight, and ensuring regular exercise and a good diet. Over time however, changes will occur in your dog's heart because of the increased work to make up for the insufficient, or leaky, mitral valve. Early signs that the heart is no longer able to compensate for mitral valve disease may include a reduced tolerance for exercise, difficulties in breathing, or a cough at night or at rest.