Dysplasia is the enlargement of an organ or tissue due to proliferation of cells. Atrioventricular Valve Dysplasia (AVD) is a congenital disorder characterized by malformation of either mitral valve or tricuspid valve.
The heart is made up of four chambers. The upper two chambers are called atria (singular atrium) and lower two chambers are called ventricles. Mitral valve is located between left atrium and left ventricle while tricuspid valve is located between right atrium and right ventricle. These valves prevent backward flow of blood into the corresponding atria when the ventricles contract.
AVD occurs due to various types of malformation in the mitral or tricuspid valve. Due to malformations, various degrees of valvular stenosis (narrowing of valves) may be present. This results in inflow obstruction (obstruction in flow of blood through atria into corresponding ventricles).
Valvular insufficiency is due to malformation of either of the valves which allows backward flow of blood from ventricle into atrium from where is just came. Since mitral and tricuspid valves are responsible to restrict backflow of blood into atria when the heart beats, valvular malformation allows backflow of the blood into atria,(known as tricuspid or mitral valve insufficiency or regurgitation) resulting in blood accumulating in corresponding atrium. To overcome this situation, the heart must work harder. 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 oppostie of valvular insufficiency is valvular stenosis (abnormal narrowing of valve opening) which causes atrial dilation and shrinking of ventricle on the same side (either left or right).
Mitral valve abnormality affects blood flow to the lungs since mitral valve is located on left side of the heart while tricuspid valve malformation affects blood flow to the rest of the body.
Certain breeds are predisposed to either mitral or tricuspid valve malformation. German shepherds, Great Pyrenees, old English sheepdogs are breeds with a higher risk of having tricuspid valve dysplasia while bull terriers, Newfoundlands, Labrador retrievers, great Danes, golden retrievers, German shepherds, and Dalmatians are the breeds with a higher risk of mitral valve dysplasia. The condition is diagnosed in most dogs in the first year.
Common symptoms associated with both mitral and tricuspid valve dysplasia include
Tricuspid valve dysplasia
Fluid or swelling in the abdomen
Mitral valve dysplasia