Adjustment of pulmonary capillary wedge pressure for wave delay increases the accuracy of mitral valve area measurement.

Pulmonary capillary wedge pressure, currently accepted as an approximation of left atrial pressure, leads to underestimation of mitral valve area calculated with the Gorlin formula. Wave delay has been pointed out as a major source of the underestimation. The aim of this study was to increase the accuracy of pulmonary artery wedge pressure-based measurements through a correction for time delay. Electrocardiogram, pulmonary capillary wedge, left atrial and left ventricular pressures were recorded simultaneously at high paper speed in 18 patients with mitral stenosis who underwent transseptal left atrial catheterization prior to mitral valvulotomy. Heart rate and wedge pressure wave delay were closely correlated (r = 0.78, p < 0.001). Linear regression equation (y = 1.1x + 8) was then applied in order to adjust the pulmonary capillary wedge pressure for time delay in every complex. Relative to mitral area measured with left atrial pressure, areas calculated using wedge pressure with and without correction were, respectively, 5 +/- 6% and 16 +/- 7% (p < 0.001) lower. Both methods showed a close correlation (r > 0.95) with measurements obtained using left atrial pressure; plotting the standard deviation against the mean, the correction of capillary wedge pressure significantly (p < 0.001) increased the accuracy of area measurement. In conclusion, pulmonary wedge pressure, properly obtained and adjusted for time delay, allows a more reliable measurement of the mitral area.