Effect of severe pulmonary hypertension on the calculation of mitral valve area in patients with mitral stenosis. We studied 50 consecutive patients with mitral valve stenosis (MS) by cardiac catheterization and Doppler echocardiography to assess whether the presence of severe pulmonary hypertension affected the calculation of valve area by Doppler pressure half-time method and by the Gorlin formula using pulmonary capillary wedge pressure as an index of left atrial pressure. Patients with severe mitral regurgitation were excluded. In patients with pulmonary artery systolic pressure (PAS) less than 70 mm Hg (n = 33), there was good correlation between the mitral valve area derived from Doppler echocardiography and from cardiac catheterization (r = 0.85). However, in patients with PAS greater than or equal to 70 mm Hg (n = 17), this correlation was not as good (r = 0.57). In these 17 patients, the Gorlin formula tended to underestimate the valve orifice area (mean valve area 0.85 +/- 0.49 and 1.06 +/- 0.46 cm2 by catheterization and by Doppler respectively, p = NS). Direct measurement of the valve area by two-dimensional echocardiography was possible in 12 of the 17 patients and correlated well with Doppler values (r = 0.91). Hence in the presence of severe pulmonary hypertension, Doppler pressure half-time estimation of mitral valve area is more accurate than is catheterization-derived valve area, using the wedge pressure and the Gorlin formula. 