Effect of mitral regurgitation and volume loading on pressure half-time before and after balloon valvotomy in mitral stenosis. Doppler pressure half-time (PHT) is frequently used to assess mitral valve area (MVA), but the reliability of PHT has recently been challenged, specifically in the setting of balloon mitral valvotomy when hemodynamics have been abruptly altered. The effect of volume loading both before and after balloon mitral valvotomy on computation of MVA by Gorlin and by PHT in 18 patients with high-fidelity micromanometer measurements of left atrial and left ventricular pressure was therefore examined. Echocardiographic MVA increased from 0.91 +/- 0.15 to 1.97 +/- 0.42 cm2 after valvotomy. Volume loading produced significant increases in left atrial pressure (16 to 23 before and 12 to 20 mm Hg after valvotomy), in cardiac output (3.7 to 4.1 before and 3.9 to 4.6 liters/min after valvotomy), and in mitral valve gradient (11 to 14 before and 5 to 7 mm Hg after valvotomy). These hemodynamic changes were associated with modest but significant decreases in PHT and increases in MVA estimated by 220/PHT (0.66 to 0.81 before and 1.64 to 1.96 cm2 after valvotomy), whereas the MVA by Gorlin was not affected in a consistent fashion by volume loading (0.85 to 0.89 before and 1.66 to 1.69 cm2 after valvotomy). The correlation between Gorlin MVA and 220/PHT was only fair (r = 0.73, p less than 0.001) and was significantly poorer among patients with greater than 1+ mitral regurgitation (r = 0.72) than among those with less or no regurgitation (r = 0.79) (p = 0.001 by analysis of covariance for mitral regurgitation effect). 