Value and limitations of Doppler echocardiographic determination of mitral valve area in Lutembacher syndrome

Department of Cardiology, All India Institute of Medical Sciences, New Delhi.

OBJECTIVES. Our objective was to compare the Doppler pressure half-time, Doppler continuity equation and two-dimensional echocardiographic planimetric methods of estimating mitral valve area in Lutembacher syndrome. BACKGROUND. Fluid dynamics theory predicts that mitral pressure half-time varies inversely with mitral valve area and directly with net chamber compliance and the peak early diastolic transmitral gradient in pure mitral stenosis. The effects of an atrial shunt on these interrelations have not been investigated. METHODS. Correlation and agreement between mitral valve area estimates obtained by the three methods and that obtained by cardiac catheterization was ascertained in 11 patients with Lutembacher syndrome. RESULTS. Valve areas determined by planimetry and the continuity equation method correlated and agreed well with catheterization measurements (r = 0.83 and 0.81, respectively). The pressure half-time method consistently overestimated mitral valve area; the extent of overestimation was greater in patients with larger atrial shunts. The hemodynamic pressure half-time was independent of the mitral valve area, chamber compliance and the peak transmitral gradient. It was dependent on the magnitude of the atrial shunt, although the correlation obtained was only fair (r = 0.61). CONCLUSIONS. These findings suggest that the Doppler pressure half-time method is an inaccurate measure of mitral valve area whenever an atrial shunt coexists with mitral stenosis. Planimetry and the Doppler continuity equation methods yield accurate estimates of mitral valve area in Lutembacher syndrome.