Merck Manual

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Understanding Stenosis and Regurgitation

Understanding Stenosis and Regurgitation

The heart valves can malfunction either by leaking (causing regurgitation) or by not opening adequately and thus partially blocking the flow of blood through the valve (causing stenosis). Stenosis and regurgitation can affect any of the heart valves. These two disorders are shown below affecting the mitral valve.

Understanding Stenosis and Regurgitation

Normally, just after the left ventricle finishes contracting and starts to relax and fill with blood again (during diastole), the aortic valve closes, the mitral valve opens, and some blood flows from the left atrium into the left ventricle. Then the left atrium contracts, ejecting more blood into the left ventricle.

As the left ventricle begins to contract (during systole), the mitral valve closes, the aortic valve opens, and blood is ejected into the aorta.

Understanding Stenosis and Regurgitation

In mitral stenosis, the mitral valve opening is narrowed, and blood flow from the left atrium into the left ventricle during diastole is reduced.

In mitral regurgitation, the mitral valve leaks when the left ventricle contracts (during systole), and some blood flows backward into the left atrium.