regurgitant fraction   =   
  
    
      
        
          
            
              
                V
                
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              −
              
                V
                
                  a
                  o
                  r
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                  c
                
              
            
            
              V
              
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        ×
        100
        %
      
    
    {\displaystyle {\frac {V_{mitral}-V_{aortic}}{V_{mitral}}}\times 100\%}
  where Vmitral and Vaortic are, respectively, the volumes of blood that flow forward through the mitral valve and aortic valve during a cardiac cycle.
Diagnosis
There are many diagnostic tests that have abnormal results in the presence of MR. These tests suggest the diagnosis of MR and may indicate to the physician that further testing is warranted. For instance, the electrocardiogram (ECG) in long-standing MR may show evidence of left atrial enlargement and left ventricular dilatation. Atrial fibrillation may also be noted on the ECG in individuals with chronic mitral regurgitation. The ECG may not show any of these findings in the setting of acute MR. The quantification of MR usually employs imaging studies such as echocardiography or magnetic resonance angiography of the heart. Chest X-ray
The chest X-ray in individuals with chronic MR is characterized by enlargement of the left atrium and the left ventricle, and then maybe calcification of the mitral valve. Echocardiogram
An echocardiogram is commonly used to confirm the diagnosis of MR. Color doppler flow on the transthoracic echocardiogram (TTE) will reveal a jet of blood flowing from the left ventricle into the left atrium during ventricular systole. Also, it may detect a dilated left atrium and ventricle and decreased left ventricular function. A transesophageal echocardiogram can give clearer images if needed as the back of the heart can also be viewed. Electrocardiography
P mitrale is a broad, bifid notched P wave in several or many leads with a prominent late negative component to the P wave in lead V1, and may be seen in MR, but also in mitral stenosis, and, potentially, any cause of overload of the left atrium.