What is MMVD?

As the name suggests, myxomatous mitral valve disease, MMVD, affects the mitral valve, which is located on the left side of the heart between the atrium and the ventricle.  MMVD is a slowly progressive condition in which the mitral valve thickens. Normally, heart valves form a perfect seal when closed ensuring that blood flows in the right direction through the heart.  Therefore the function of the mitral valve is to channel blood from the left atrium into the left ventricle.  However, in MMVD the thickening of the mitral valve results in an imperfect seal and allows blood to “leak” backward into the atrium as the ventricle contracts.

How prevalent is MMVD?

MMVD affects about:

• 10% of dogs between the ages of 5 and 8 years
• 25% of dogs between the ages of 9 and 12 years
• 35% of dogs more than 13 years

This form of heart disease usually occurs in small-to medium-size dogs. The most susceptible breeds are Cavalier King Charles Spaniels, Poodles, Schnauzers, Chihuahuas, and Fox Terriers. Also, male dogs are more commonly affected than females.