Quantification of mitral regurgitation with the proximal flow convergence method: A clinical study

Accurate quantitation of valvular incompetence remains an important goal in clinical cardiology. It has been shown previously that when color flow Doppler mapping is used, simple measurements of apparent jet size do not correlate closely with regurgitant flow rate and regurgitant fraction. Recently the proximal flow convergence method has been proposed to quantify valvular regurgitation by analysis of the converging flow field proximal to a regurgitant lesion. Flow rate Q can be calculated as Q = 2πr²v_a, where v_a is the aliasing velocity at a distance r from the orifice. In 54 patients (43 with sinus rhythm and 11 with atrial fibrillation) who had at least mild mitral regurgitation according to semiquantitative assessment, regurgitant stroke volume, regurgitant flow rate, and regurgitant fraction were calculated with the proximal flow convergence method and compared with values that were obtained by the Doppler two-dimensional echocardiographic method. Regurgitant stroke volumes (V_r) as calculated by the proximal flow convergence method correlated very closely with values that were obtained by the Doppler two-dimensional method, with r = 0.93 (y = 0.95x + 0.55) and ΔV_r = -0.3 ± 4.0 cm³. Regurgitant flow rates (Q) as calculated by both methods showed a similar correlation: r = 0.93 (y = 0.95x + 54) and ΔQ = -34 ± 284 cm³/min. The correlation for regurgitant fraction (RF) as calculated by both techniques showed r = 0.89 (y = 0.98x + 0.006) and ΔRF = -0.005 ± 0.06. All correlations were slightly better for the group of patients with sinus rhythm than for the study group of patients with atrial fibrillation. This study demonstrates that the proximal flow convergence method is an accurate and reproducible technique to quantify mitral regurgitation in patients with at least mild mitral regurgitation. This approach is easy and less time-consuming than the Doppler echocardiographic method. Although future refinements of this method are to be expected, flow calculations that are based on the assumption of simple hemispheric symmetry of the proximal flow field show excellent results and appear to be suitable for clinical application at present.