Mitral Insufficiency-Moderate

Mitral insufficiency is due to a degeneration of the mitral valve. With moderate insufficiency, since a significant amount of blood is now moving back and forth within the left side of the heart, the left atrium especially starts to enlarge to accommodate the increased volume of blood

Disease Info

Mitral Insufficiency (MI)- Moderate

(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
        • with moderate insufficiency, since a significant amount of blood is now moving back and forth within the left side of the heart, the left atrium especially starts to enlarge to accommodate the increased volume of blood
    • 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 (with moderate mitral insufficiency):

    • These pets may show signs of “slowing down”, and are often attributed to age
      • Cough can be present due to the enlarging heart pressing up on the bronchus (lower airway)
  • 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 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)


  • THERAPY
    • Therapy at this stage is somewhat controversial, though growing evidence for earlier intervention continues to grow
    • Deciding to intervene at this time often is determined by specific diagnostic findings with echocardiography, radiographs, blood pressure, or electrocardiogram
      • Inodilators (pimobendan)
        • Make the heart pump blood forward more effectively
          • Early use of this medication has been shown to not only delay the onset to congestive heart failure, but also increase survival once a pet has gone into congestive heart failure
      • Vasodilators (amlodipine, benazepril, enalapril, hydralazine, others)
        • decrease blood pressure and make it easier for the heart to pump effectively
          • Since high blood pressure can adversely affect the heart, controlling systemic hypertension may be warranted
      • Hormone system control (benazepril, enalapril, spironolactone)
        • In heart disease, circulating hormones get activated that make the disease progress
          • In some cases, decreasing these circulating hormones can improve survival
      • Rhythm disturbance control (Digoxin, Diltiazem, Mexilitine, Sotalol, others)
        • This is pretty uncommon in moderate mitral insufficiency, but occasionally…
      • Dietary
        • We generally do not change foods at this time
          • We do want you to avoid high salt foods
          • Lunch meats, salted popcorn, potato chips, etc
      • Exercise
        • Your pet should be able to exercise normally
          • But be aware it is taking some extra effort for them to perform at their former level
  • PROGNOSIS
    • For the short term, excellent
    • Many of these pets will progress onward to significant disease, though this can take years to occur
  • 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
    • Monitoring
      • Monitoring at home consists of monitoring eating and activity, and to note breathing and coughing patterns. Because fluid in the lungs causes increased breathing rates as the first sign of congestive heart failure, noting breathing rates is very important, although usually does not happen for quite a while in these cases. See our Resting Breathing Rates page
      • How and how often they should be monitored really seems to vary by the cardiologist or practitioner
        • At this stage we will be recommending either repeat echocardiograms (heart ultrasounds) or radiographs (X-rays) at intervals based on your pets individual condition

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. Cough can be present due to the enlarging heart pressing up on the bronchus (lower airway)
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. Many of these pets will progress onward to significant disease, though this can take years to occur
FOLLOW UP CARE: Monitoring at home consists of monitoring eating and activity, and to note breathing and coughing patterns. At this stage we will be recommending either repeat echocardiograms (heart ultrasounds) or radiographs (X-rays) at intervals based on your pets individual condition