Physiologic Application of the Proximal Flow Convergence Method: Clinical Data and Experimental Testing

Background The proximal flow convergence method, a quantitative color Doppler flow technique, has been validated recently for calculating regurgitant flow and orifice area. We investigated the potential of the method as a tool to study different pathophysiological mechanisms of mitral valve incompetence by assessing the time course of regurgitant flow and orifice area and analyzed the implications for quantification of mitral regurgitation. Methods and Results Fifty-six consecutive patients with mitral regurgitation of different etiologies were studied. The instantaneous regurgitant flow rate Q(t) was computed from color M-mode recordings of the proximal flow convergence region and divided by the corresponding orifice velocity V(t) to obtain the instantaneous orifice area At). Regurgitant stroke volume (RSV) was obtained by integrating Q(t). Mean regurgitant flow rate Qm was calculated by RSV divided by regurgitation time. Peak-to-mean regurgitant flow rates Qp/Qm and orifice areas Ap/Am were calculated to assess the phasic character of Q(t) and A(t). In the first 24 patients (group 1), computation of Qm and RSV from the color Doppler recordings was compared with the conventional pulsed Doppler method (r=.94, SEE=29.4 mL/s and r=.95, SEE=9.7 mL) as well as with angiography (r,=.93 and r,=.94, P<.001). The temporal variation of Q(t) and A(t) was studied in the next 32 patients (group 2): In functional regurgitation in dilated cardiomyopathy (n= 12), there was a constant decrease in At) throughout systole with an increase during left ventricular relaxation; Ap/Am was 5.49±3.17. In mitral valve prolapse (n=6), A(t) was small in early systole, increasing substantially in midsystole, and decreasing mildly during left ventricular relaxation; Ap/Am was 2.48±0.26. In rheumatic mitral regurgitation (n= 14), a roughly constant regurgitant orifice area during most of systole was found in 4 patients. In the other patients there was significant variation of ASt) and the time of its maximum; Ap/Am was 1.81 ±0.56. ANOVA demonstrated that