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What is the mitral valve?
By Ernest Ward, DVM

The heart has four chambers. The upper chambers are called atria (one chamber is called an atrium) and the lower chambers are called ventricles. The heart is also divided into right and left sides.

Each chamber of the heart has a one-way valve to keep blood from flowing backward. The valve between the left atrium and left ventricle is called the mitral valve.

What causes mitral valve disease?
Unoxygenated blood returns from the body to the heart by entering the right atrium (right upper chamber). It is stored there briefly and then pumped into the right ventricle (right lower chamber). The right ventricle pumps blood into the lungs where it picks up oxygen. Oxygenated blood flows from the lungs into the left atrium (left upper chamber) where it is held before flowing into the left ventricle. From the left ventricle, oxygen-rich blood is pumped throughout the body through the aorta and the arteries. The left ventricle is surrounded by the largest and strongest of the heart muscles. This large muscle is necessary to pump blood out of the heart and throughout the body.
Because of the high pressure created when the left ventricle contracts and pumps blood out to the body, the mitral valve may begin to “wear out” and leak over time. This is known as mitral valve insufficiency (MVI) or mitral regurgitation and is often associated with a heart murmur. Other causes of mitral valve insufficiency include ruptured chordae tendinae, a condition in which the fibrous cords that hold the valve leaflets in position break and heart valve infections known as endocarditis. Endocarditis may result from blood-borne infections or, more commonly, may be secondary to chronic oral infections (periodontal disease).

How common is mitral valve disease?
Approximately one in ten dogs (10%) will develop some form of heart disease during their lifetime, and approximately 80% of the heart disease is due to mitral valve insufficiency. MVI is more common in small dogs than large breeds. Read More…

Related Links
Learn more about cardiac disease testing and health screening certification through the Orthopedic Foundation For Animals
Current research from the Canine Health Foundation

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