Chronic mitral regurgitation occurs when the mitral valve in the heart fails to close tightly. This allows some oxygen-rich blood to flow back into the heart rather than out into the body.

What is going on in the body?

The left side of the heart has two chambers:

Between them lies a one-way valve that allows blood to flow from the atrium to the ventricle. It is the mitral valve.

The left ventricle is the main pumping chamber of the heart. The mitral valve opens to allow the ventricle to fill. It closes as the ventricle contracts and ejects oxygen-rich blood into the aorta, the major artery in the body. This blood is then sent throughout the body.

If the mitral valve fails to close tightly, some blood is pumped back into the atrium when the ventricle contracts. This lessens the flow of blood to the rest of the body. The left ventricle then pumps harder to compensate for the decreased blood flow.

The build-up of blood in the left atrium puts pressure on the lungs and a chamber on the right side of the heart called the right ventricle. This can cause right ventricular failure. Elderly people often have minor problems or minor regurgitation in the mitral valve. Such problems cause little or no heart trouble. With larger mitral valve defects, though, the left atrium and ventricle enlarge over time. Congestive heart failure and abnormal heart rhythms, or arrhythmias, can follow.

What are the causes and risks of the condition?

A wide variety of conditions can cause mitral regurgitation. Generally speaking, any condition that changes the shape, structure, or function of the mitral valve or its attachments to the heart can cause this condition. These include:

Irregular heart rhythms, or arrhythmias, may be due to enlargement of the left atrium.