Quantification of mitral regurgitation by the proximal convergence method using transesophageal echocardiography: Clinical validation of a geometric correction for proximal flow constraint

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=2Πr² V(a)/V(p) and RSV=ROAxVTI(ew), where r and v(a) are the radius and velocity of the aliasing contour and v(p) and VTI(ew) 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 cm²) 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 cm²), 68% of whom had leaflet prolapse or flail. ΔRSV was correlated with a (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 cm²) 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.