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| {{CMG}}
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| '''Associate Editor-In-Chief:''' {{CZ}}; [[Varun Kumar]], M.B.B.S.; [[Lakshmi Gopalakrishnan]], M.B.B.S.
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| {{Editor Help}}
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| <table border="1" cellpadding="5" cellspacing="0" align="right">
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| <caption>'''Determination of the degree of mitral regurgitation'''</caption>
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| <tr>
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| <th style="background:#efefef;">Degree of mitral regurgitation</th>
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| <th style="background:#efefef;">Regurgitant fraction</th>
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| <th style="background:#efefef;" width="100px">Regurgitant Orifice area</th>
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| </tr>
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| <tr><td>Mild mitral regurgitation</td><td>< 20 percent</td></tr>
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| <tr><td>Moderate mitral regurgitation</td><td>20 - 40 percent</td></tr>
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| <tr><td>Moderate to severe mitral regurgitation</td><td>40 - 60 percent</td></tr>
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| <tr><td>Severe mitral regurgitation</td><td>> 60 percent</td><td>> 0.3 cm<sup>2</sup></td></tr>
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| </table>
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| The degree of severity of mitral regurgitation can be quantified by the percentage of the left ventricular stroke volume that regurgitates into the left atrium (the regurgitant fraction).
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| Methods that have been used to assess the regurgitant fraction in mitral regurgitation include echocardiography, cardiac catheterization, fast CT scan, and cardiac MRI.
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| The echocardiographic technique to measure the regurgitant fraction is to determine the forward flow through the mitral valve (from the left atrium to the left ventricle) during ventricular [[diastole]], and comparing it with the flow out of the left ventricle through the aortic valve in ventricular [[systole]].
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| This method assumes that the aortic valve does not suffer from [[aortic insufficiency]]. The regurgitant fraction would be described as:
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| <center><math>\frac{forward\ flow\ through\ the\ mitral\ valve - flow\ through\ the\ aortic\ valve} {forward\ flow\ through\ the\ mitral\ valve}</math></center>
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| Another way to quantify the degree of mitral regurgitation is to determine the area of the regurgitant flow at the level of the valve. This is known as the regurgitant orifice area, and correlates with the size of the defect in the [[mitral valve]].
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| One particular echocardiographic technique used to measure the orifice area is measurement of the [[proximal isovelocity surface area]] (PISA). The flaw of using PISA to determine the mitral valve regurgitant orifice area is that it measures the flow at one moment in time in the cardiac cycle, which may not reflect the average performance of the regurgitant jet.
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