Accurate measurement of the transmitral gradient in patients with mitral stenosis: A simultaneous catheterization and Doppler echocardiographic study

Objectives. This study compared the accuracy of Doppler echocardiography with that of conventional cardiac catheterization in the measurement of transmitral gradients in patients with mitral stenosis. Background. Simultaneous measurement of left atrial and left ventricular pressures is the most accurate method for determination of the mean mitral valve gradient in patients with mitral stenosis. Because of the inherent risks of transseptal catheterization, pulmonary capillary wedge pressure has been used in many invasive laboratories for determination of the mean mitral valve gradient. Recent studies have observed significant errors when pulmonary capillary wedge pressure was used for these measurements. Doppler echocardiography provides a noninvasive alternative for measurement of the transmitral gradient, but its relative accuracy has remained unclear. Methods. Seventeen patients with mitral stenosis who underwent transseptal cardiac catheterization had simultaneous measurement of 1) transmitral gradient by direct left atrial and left ventricular pressures, 2) transmitral gradient by pulmonary capillary wedge and left ventricular pressures, and 3) transmitral gradient by Doppler echocardiography. Results. Transmitral gradient measured by pulmonary capillary wedge and left ventricular pressures significantly overestimated the gradient obtained by direct measurement of left atrial pressure, with a mean (±SD) difference of 3.3 ± 3.5 mm Hg (or 53%). Correcting the pulmonary capillary wedge pressure for the phase shift resulted in better correlation, but a consistent overestimation still remained, with a mean difference of 2.5 ± 2.9 mm Hg (or 43%). The best correlation with the smallest variability was comparison of the Doppler-derived mean gradient with the gradient from direct measurement of left atrial and left ventricular pressures, with a mean difference of 0.2 ± 1.2 mm Hg. Conclusions. Compared with the transmitral gradient obtained by direct measurement of left atrial and left ventricular pressures, the Doppler-derived gradient is more accurate than that obtained by conventional cardiac catheterization and should be considered the reference standard.