Quantification of Mitral Regurgitation by the Proximal Convergence Method Using Transesophageal Echocardiography

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Abstract
Background Proximal flow convergence is a promising method to quantify mitral regurgitation but may overestimate flow when the flow field is constrained. This has not been investigated clinically, nor has a correction factor been validated. Methods and Results Eighty-five patients were studied intraoperatively with transesophageal echocardiography and divided into two groups: central convergence (no constraining wall) and eccentric convergence (at least one constraining wall). Regurgitant stroke volume (RSV) and orifice area (ROA) were calculated by ROA=2π r 2 V a /V p and RSV=ROA×VTI cw , where r and v a are the radius and velocity of the aliasing contour and v p and VTI cw are the peak and integral of regurgitant velocity. In eccentric convergence patients, convergence angle (α) was measured from two-dimensional Doppler color flow maps, and ROA and RSV were corrected by multiplying by α/180. For reference, RSV was the difference between thermodilution and pulsed Doppler stroke volumes. In central convergence patients (n=45), RSV ( r =.95, Δ=2.5±10.8 mL) and ROA ( r =.96, Δ=0.02±0.08 cm 2 ) were accurately calculated, but significant overestimation was noted in the eccentric convergence patients (n=40, ΔRSV=63.9±38.0 mL, ΔROA=0.54±0.31 cm 2 ), 68% of whom had leaflet prolapse or flail. ΔRSV was correlated with α ( r =–.69, P <.001). After correction by α/180, overestimation was largely eliminated (ΔRSV=15.5±19.3 mL and ΔROA=0.14±0.14 cm 2 ) with excellent correlation for the whole group (RSV, r =.91; ROA, r =.95). Conclusions A simple geometric correction factor largely eliminates overestimation caused by flow constraint with the proximal convergence method and should extend the clinical utility of this technique.