Doppler estimation of pressure gradient in pulmonary stenosis: maximal instantaneous vs peak-to-peak, vs mean...

We undertook a study to identify the hemodynamic significance of a Doppler-derived gradient across a stenotic pulmonary valve. Furthermore, we attempted to define the optimal plane for velocity data acquisition. A total of 17 children with valvar pulmonary stenosis were evaluated using Doppler echocardiography. Flow-velocity profiles were obtained from both the parasternal and subxiphoid windows. Ten of 17 patients were studied before and after balloon valvotomy. Therefore, 27 different transvalvar gradients were assessed by Doppler and these data were compared with the catheter-derived maximal instantaneous, peak-to-peak, and mean pressure gradients. The maximal Doppler gradient correlated well with the catheter-derived peak-to-peak pressure gradient (r = 0.95) and catheter maximal instantaneous pressure gradient (r = 0.95). Although these correlation coefficients were similar, the Doppler maximal gradient consistently overestimated the peak-to-peak catheter gradient by as much as 25%-40%. Such an overestimation was not observed when we compared the maximal Doppler gradient with the catheter-derived maximal instantaneous gradient. Moreover, the regression line of the latter comparison closely approximated the line of identity. The correlation coefficient between Doppler mean and catheter mean gradients was only 0.91. Doppler velocities were best derived when multiple transducer positions were employed to interrogate pulmonary artery velocity.