Mitral Insufficiency

(also called mitral regurgitation (MR), chronic degenerative valve disease (CVD), myxomatous degeneration or endocardiosis )

Disease Info

Mitral Insufficiency (MI)

(also called mitral regurgitation (MR), chronic degenerative valve disease (CVD), myxomatous degeneration or endocardiosis )

Mitral Insufficiency or Mitral Regurgitation


  • DEFINITION (What it is):
    • Mitral insufficiency is due to a degeneration of the mitral valve, which separates the left atrium (the receiving chamber) from the left ventricle (the pumping chamber)
      • The valve starts leaking backwards, so that blood flows both forward and backward within the heart.
        • There are varying amounts of leak
          • This usually (but not always) corresponds to how enlarged the chambers get
    • This is an age related degenerative process, and not related to infection or inflammation
  • EPIDEMIOLOGY (Who gets it):
    • Mitral insufficiency is a disease of small breed dogs, though we see occasional cases in medium and large breed dogs
      • It is very common, seen in about 75% of all canine heart cases
        • about 30% of cases will have degeneration of both the mitral and tricuspid valves
        • about 10% of cases will have only tricuspid valve degeneration (see Tricuspid Insufficiency)
      • These breeds include miniature Poodles, minature Schnauzers, terriers, Dachsunds and American Cocker Spaniels.
        • Cavalier King Charles Spaniels
          • are at increased risk for developing the disease
          • occurs earlier in this breed
      • It occurs in older pets
        • > 5 years
    • It is very rare in cats


  • CAUSE:
    • Mitral insufficiency is due to age-related degeneration of the valve
      • It appears to be related to collagen disorganization at the cellular level
      • It is not related to
        • infection
        • inflammation
        • dental disease (though dental health is important for your pet)
      • There is probably a genetic component since we see this commonly in certain breeds, but these genes have not been identified
  • CLINICAL SIGNS:
    • This depends on the severity of the disease, and we have provided specific breakdowns for you

      • These pets may show signs of “slowing down”, and are often attributed to age
      • Exercise intolerance
      • Weakness
      • Fainting
      • Cough
      • Fast or difficult breathing
  • DIAGNOSTICS (See Tests We Often Perform)

    • Echocardiography (heart ultrasound)
      • Staging of the mitral valve disease is typically performed with echocardiography (heart ultrasound)
    • Doppler Blood Pressure
      • We often will want a blood pressure to make sure blood pressure is not too high and causing progression of disease
    • Radiographs (x-rays)
      • If cough is present, radiographs (x-rays will be recommended)
    • Electrocardiogram
      • Very occasionally, there are heart rhythm disturbances that require and electrocardiogram (ECG or EKG)
    • Laboratory testing is often necessary, especially if we are going to start medications that may affect the kidneys


  • THERAPY
    • Therapy is very dependent on the stage of the clinical disease. See the appropriate level of disease for your pet.
  • PROGNOSIS
    • Prognosis is very dependent on the stage of the clinical disease. See the appropriate level of disease for your pet.
  • FOLLOW UP CARE
    • We understand that your money has to be spent wisely to be able to monitor and treat your pet for it’s lifetime, so we are very respectful of your finances and yet provide excellent care for your pet
      • We work as a team with your family veterinarian, and maintaining routine and non-specialist care is a very important part of our consideration
    • Follow up care is very dependent on the stage of disease. See the appropriate level of disease for your pet.

Quick Info

DEFINITION (What it is): Mitral insufficiency is due to a degeneration of the mitral valve, which separates the left atrium (the receiving chamber) from the left ventricle (the pumping chamber)
EPIDEMIOLOGY (Who gets it): Mitral insufficiency is a disease of small breed dogs
CAUSE: Mitral insufficiency is due to age-related degeneration of the valve
CLINICAL SIGNS: These pets may show signs of "slowing down", and are often attributed to age
POSSIBLE DIAGNOSTICS: Echocardiography (heart ultrasound), Doppler Blood Pressure, Radiographs (x-rays), Electrocardiogram
THERAPY: Therapy at this stage is somewhat controversial, though growing evidence for earlier intervention continues to grow
PROGNOSIS: For the short term, excellent
FOLLOW UP CARE: At this stage we will be recommending either repeat echocardiograms (heart ultrasounds) or radiographs (X-rays) at intervals based on your pets individual condition