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Heart Valve Malformation in Dogs

Atrioventricular Valve Dysplasia in Dogs

Dogs with malformed mitral or tricuspid valves are said to have atrioventricular valve dysplasia (AVD). This condition can result in the valves not closing sufficiently to stop blood flow when it supposed to, or to blood outflow obstruction due to a narrowing of the valves. The result of the malformation will depend on the size and location of the anatomic abnormality that is present.

Valvular insufficiency causes the atrium on the same side as the affected valve (right or left) to be dilated and the ventricle to enlarge. Over time, this chronic volume overload raises atrial pressures and causes blood to build up in the lungs (if the mitral valve is malformed) or pool in the body (if the tricuspid valve is malformed). The opposite malformation, valvular stenosis, a narrowing of the valve, causes atrial dilation along with shrinkage of the ventricle on that same side.

Abnormality in the mitral valve, for example, affects blood flow to the lungs because it located on the left side of the heart, while the tricuspid valve, found on the right side of the heart, affects blood flow to the rest of the body.

These types of dysplasias are more common in some dog breeds. Tricuspid valve dysplasia is often seen in German shepherds, Great Pyrenees, old English sheepdogs, and is recessive in Labrador Retrievers. Mitral valve dysplasia is more often seen in bull terriers, Newfoundlands, Labrador retrievers, great Danes, golden retrievers, German shepherds, and Dalmatians. In addition, male animals are more likely to develop heart failure as a result of this condition.

Congenital valvular defects are most often diagnosed in a dog's first few years of life.

Symptoms and Types

Tricuspid valve dysplasia

  • Stunted growth
  • Loud breathing
  • Fluid or swelling in the abdomen

Mitral valve dysplasia

  • Exercise intolerance
  • Trouble breathing/coughing
  • Fainting

Causes

  • Congenital (malformation present at birth); suspected of being of genetic origin

Diagnosis

You will need to give a thorough history of your dog's health and onset of symptoms, including any information you have on your dog's family line. A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, and a urinalysis. The results of these tests typically return normal levels. Based on the apparent symptoms and the results of the initial physical exam, your veterinarian should be able to narrow the cause down to which type of heart valve disease is present. This will need to be confirmed with further testing.

For diagnostic purposes, your veterinarian will need to view the heart using imaging tools. X-rays can help your veterinarian to determine if there is enlargement of the valves or atrium on either side of the heart, and echocardiography will show atrial dilation, and possibly abnormal flow of the blood through the heart, in the case of tricuspid valve dysplasia. Electrocardiograph readings can also help your doctor to determine if the heart's electrical functioning is being affected. An abnormal rhythm, and the exact measurement of the abnormality can be a great help in determining which side of the heart is most affected.

 
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