Value and limitations of Doppler pressure half-time in quantifying mitral stenosis: A comparison with micromanometer catheter recordings

The purpose of this study was to compare the Doppler and catheterization pressure half-time methods of estimating mitral valve area with valve areas obtained by the Gorlin equation in a group of patients with clinically significant mitral stenosis. Data were analyzed from 67 consecutive patients who were undergoing continuous-wave Doppler examination and catheterization with micromanometer catheters. Doppler pressure half-time was calculated as the interval between peak transmitral velocity and velocity divided by the square root of 2, as measured from the outer border of the spectral envelope. Doppler mitral valve area (MVA) was obtained with the equation: MVA = 220 ÷ pressure half-time. For catheterization data, the pressure half-time was measured directly from simultaneously recorded left ventricular and left atrial pressure (18 patients) or pulmonary capillary wedge pressure (49 patients). The catheterization half-time was taken as the time required for the peak pressure gradient to fall to one half of the initial value. Calculations of the mitral valve area at catheterization were obtained by the Gorlin equation with pressure gradient and cardiac output determinations. Mitral valve area as determined by the Gorlin equation for all cases ranged from 0.4 to 2.0 (mean = 1.03 ± 0.37) cm². Linear regression analysis that compared cardiac catheterization and Doppler half-times yielded r = 0.68. For the subgroup of patients with sinus rhythm, the correlation improved to r = 0.76. A comparison of Doppler-derived mitral valve area with the use of the half-time method and Gorlin-derived valve areas resulted in r = 0.80 with an exponential curve fit with CATH PHT = 228 (MVA)^-63, where CATH PHT is catheterization pressure half time. When patients were analyzed by subgroup according to the presence of atrial fibrillation and mitral regurgitation, correlations between Doppler- and Gorlin-derived valve areas showed: r = 0.84 for patients with sinus rhythm and 0 to 1+ mitral regurgitation (n = 37); r = 0.76 for patients with atrial fibrillation and 0 to 1+ mitral regurgitation (r = 17); r = 0.01 for sinus rhythm and 2 to 4+ mitral regurgitation; (n = 7); and r = 0.33 for the group with atrial fibrillation and 2 to 4+ mitral regurgitation (n = 6). Thus our data show that both catheterization and Doppler pressure half-times are fair predictors of Gorlin-derived mitral valve area within a clinically relevant range of mitral stenosis. However, the relationship of pressure half-time to valve area is best described by an exponential equation. The Doppler half-time valve area is clinically useful for valve areas less than 2.0 cm², but agreement with catheterization-derived Gorlin valve areas appears to be adversely affected by the presence of atrial fibrillation and significant mitral regurgitation.