Assessment of Mitral Valve Area in Patients with Mitral Stenosis Using Color Doppler Proximal Isovelocity Surface Area Method

ABSTRACT

BACKGROUND: It has been proposed recently that measuring the flow convergence region proximal to an orifice by Doppler flow mapping can provide a means of calculating regurgitant flow rate. And this method also can be used to derive cardiac output or flow rate proximal to stenotic orifices and therefore to calculate their areas by the continuity equation(area=flow rate/velocity). Applying this method in mitral stenosis would provide a unique way of validating the underlying concept because the predicted areas could be compared with those measured directly by planimetry and pressur half-time method. METHOD: We studied 50 patients with mitral stenosis using imaging and Doppler echocardiography. Doppler color flow recordings of mitral inflow were obtained from the apex, and the radius of the proximal flow convergence region was measured at its peak diastolic valve from the orifice to the first color alias along the axis of flow. Flow rate was calculated assuming uniform radial flow convergence toward the orifice, modified by a factor that accounted for the inflow funnel angle formed by the mitral leaflets. Mitral valve area was then calculated as peak flow rate divided by peak velocity by continuous-wave Doppler. RESULTS: The calculated areas agreed well with those from comparative techniques. 1) Cross-sectional area by planimetry(y=0.38×+0.81, r=0.51, p < 0.001). 2) Area derived from the Doppler pressure half-time(y=0.35+0.55, r=0.44, p=0.002). 3) Agreement with planimetry was similar for 26 patients with mitral regurgitation and 24 without it, as well as for 34 in atrial fibrillation. CONCLUSION: These results suggested that the proximal flow convergence concept in the clinical setting demonstrate calculating method of mietral valve area in patients with mitral stenosis.