Note for Pet Owners:
If you have an animal diagnosed as having this disorder there are some important guidelines that you should follow:

  • Always give the medications that your veterinarian has prescribed at the correct dose and at the correct times
  • Contact your veterinary practice if you are concerned that your animal is having a relapse, or if it appears to react abnormally following treatment. Your observations may simply be normal side-effects to the treatment - but they may not be and, even if they are common side-effects, the drug dosage may need to be altered.
  • The condition may not be confirmed as genetically inherited in your animal - but you should assume that it could be, and so you must prevent your animal from mating and passing on the defect to another generation.

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Atrioventricular valve dysplasia is a
congenital abnormality of either the left (mitral) or left (tricuspid) valve which separate the ventricles from the corresponding atrial chambers. Many different anatomical abnormalities can occur and tricuspid dysplasia may also be associated with a defect (hole) in the wall of the septum separating the two atria - called an atrial septal defect.

Presenting signs and history
Affected animals have an abnormal heart sound when listened to with a stethoscope (called a heart murmur) which is the typical sound that is caused by a leaking valve. Clinical signs usually occur before 1 year of age and they are not specific for the disease, but are typical for
right-sided or left-sided heart failure.

Breed Occurrence
These diseases are thought to be hereditary.

Atrioventricular abnormalities occur most frequently in large and giant breeds of dog including the
German Shepherd Dog,Great Dane, Labrador Retriever and Old English Sheepdog. Mitral stenosis has been reported in the English Bull Terrier in the UK and in the Mastiff..

Endocardial cushion defects are quite common in cats and may also involve defects (holes) in the septum separating the two atria (atrial septal defects), and notched or cleft atrioventricular valves. Tricuspid valve dysplasia is reported to be common in domestic shorthaired cats.

The only form of long-term treatment is open heart surgery and replacement of the affected valve but there are very few veterinary centres in which this procedure is performed

Treatment is otherwise designed to minimise the signs of exercise intolerance, cough, abdominal swelling (ascites) etc that are due to congestive heart failure:

  1. Reduce the workload on the heart:
    1. Rest
    2. Reduce arterial pressure (afterload) and venous pressures (preload) on the heart by the use of vasodilator drugs - benazepril, enalapril, hydralazine, nitroglycerine. Diuretics can reduce preload through fluid loss from the circulation.
    3. Weight loss in obese animals

  2. Reduce volume overload and dilation of the heart. By the use of diuretics (e.g. frusemide), the use of ACE-inhibitors (enalapril and benazepril) or venodilators (e.g. nitroglycerine) and restriction of salt intake.

  3. Improve cardiac muscle efficiency
    1. Positive inotropic drugs (e.g. digoxin, pimobendan)
    2. Controlling any dysrhythmias - e.g. slow an increased heart rate (tachycardia)
    3. Improve blood supply to the heart muscle by the use of calcium antagonists that dilate the coronary blood vessels.


Updated January 2016