A Comparative Study of the echocardiographic Methods Assessing Severity of Stenosis in Pateints with mitral Stenosis

ABSTRACT

BACKGROUND: Determination of mitral valve area (MVA) in patients with mitral stenosis is very important in clinical practice. Therefore, the ability to assess accurately MVA by noninvasive technique is of great meaning to the management of patients with mitral stenosis. Echo-Doppler(ED) method was derived from the study of fluid dynamics that the flow volume is proportional to orifice area, velocity of flow which shows period requird by the flow. It has been proposed recently that measuring the flow convergence region proximal to an orifice by Doppler flow mapping 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 these methods 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 pressure half-time method. Valve resistance has been proposed as an alternative hemodynamic indicator, but initially this index was not used because it was unlikely to remain constant at different flow rates. Recently valve resistance provided a better indices of hemodynamic obstruction than mitral valve area, and these indices usually estimated by invasive method, but it is able to calculate from Doppler echocardiography and compared to the results of invasive method. METHODS: The mitral inflow volume can be obtained by estimating the stroke volume (SV) by Teichholz's method from M-mode echocardiogram of the left ventricle, and the mean diastolic velocity(MDV) and diastolic filling period (DFP) by mitral inflow continuous-wave Dopler echocardiogram. Therefore, Echo-Doppler method is MVA=SV/MDV×DFP. 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 value from the 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. To Compare the stenotic indices from noninvasive method and invasive method, cardiac catheterization was performed. RESULTS: 1) ED-MVA of these 28 patients with mitral stenosis correlated well at a coeffitient of 0.867 than PHT-MVA(r=0.513) or 2DE(r=0.513) in comparison with Cath-MVA. 2) Excluding 4 patients with mitral regurgitation, the ED-MVA of 24 patients with isolated mitral stenosis showed a better correlation with r=0.944 than with PHT-MVA(r=0.642) or 2DE-MVA(r=0.647) in comparison with Cath-MVA. 3) MVA determined by PISA method were correlated with planimetry method on 2DE(r=0.51, p < 0.001). 4) MVA determined by PISA method were correlated with PTH method(r=0.44, p=0.002). 5) Agreement with planimetrymethod was similar for 26 patients with mitral regurgitation and 24 without it, as well as for 34 in atrial fibrillation. 6) The correlation coefficient of mitral valve area and mitral valve resistance between echocardiography(r=0.87) and cardiac catheterization(r=0.82) showed positive correlation(p < 0.001). 7) Linear regression analysis showed a negative correlation of mitral valve resistance and Gorlin mitral valve area between echocardiography (r=−0.84) and cardiac catheterization(r=−0.84). CONCLUSION: Echocardiographic evaluation of mitral valve stenosis by planimetry, pressur half-time method, Echo-Doppler method, PISA method, and mitral valve resistance were useful noninvasive methods in assessing the severity of mitral stenosis. In mitral stenosis patients with mitral regurgitation and/or aortic regurgitation, PISA and mitral valve resistance methods were also reliable. In conclusion, these results suggested that the echocardiographic methods could be sufficient for assessing the severity of mitral stenosis without the necessity of invasive technique.