= Mitral regurgitation
\b[Mitral regurgitation] is backward <blood flow> from the <left ventricle> into the <left atrium> through the <mitral valve> during ventricular <systole>. Incomplete leaflet <coaptation> permits a second outflow route while ventricular <pressure> drives forward ejection through the <aortic valve>. The imaging framework distinguishes primary leaflet disease from secondary dysfunction associated with the surrounding ventricular apparatus.<Recommendations for Noninvasive Evaluation of Native Valvular Regurgitation by William A. Zoghbi and others>[Section III, Mitral Regurgitation; III.B, primary and secondary mechanisms]{ref}
An original volume balance separates total ventricular emptying from forward output. Suppose there is no other abnormal communication and no appreciable inlet flow during the chosen systolic interval. Then
$$
V_{\rm LV,ejected}=V_{\rm aortic,forward}+V_{\rm regurgitant}.
$$
For stipulated total ejection 90 mL and forward aortic ejection 60 mL, the <regurgitant volume> is 30 mL and the <regurgitant fraction> relative to total ejection is $30/90=1/3$. Reporting only the 90 mL volume change would not identify how much reached the forward outlet. The technical report describes this complementary ventricular-volume/aortic-flow approach.<Recommendations for Noninvasive Evaluation of Native Valvular Regurgitation by William A. Zoghbi and others>[Figure 8, page 316; Section III.H.2]{ref}
Backward volume also depends on duration, not just instantaneous speed. For a chosen outlet surface $A(t)$ with normal directed toward the <left atrium>,
$$
V_{\rm regurgitant}=\int_{\rm systole}\int_{A(t)}\boldsymbol u\mathbin{\cdot}\boldsymbol n\,dA\,dt.
$$
This defines an integrated transport quantity. A short high-speed episode and a longer lower-speed episode can have the same integral, and a single peak <velocity> supplies neither surface area nor duration.
Consequently, leaflet anatomy, <mitral coaptation index>, <regurgitant volume> and chamber remodeling are distinct observations. <Doppler echocardiography> relates measured motion to flow, while anatomical imaging identifies the moving structures. Combining these measurements makes the question of leakage more precise than treating any one image dimension as a complete measure of <mitral regurgitation>.
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