Doppler ultrasound evaluation of valvar pulmonary stenosis from multiple transducer positions in children requiring pulmonary valvuloplasty.

The modified Bernoulli equation has been used to determine the peak pressure difference across stenotic pulmonary valves. The direction of the poststenotic jet may be eccentric in relation to the axis of the pulmonary artery. Consequently, the maximal velocity obtained from the parasternal transducer position may inaccurately estimate peak pressure difference. Thus, Doppler-derived estimates of pressure difference from the parasternal, subcostal, apical, and suprasternal notch transducer positions were compared with peak-to-peak pulmonary artery to right ventricle catheter withdrawal pressure differences in 24 patients admitted for pulmonary valvuloplasty. Suprasternal, subcostal or apical transducer positions produced higher maximal velocities than the parasternal transducer position in 12 of 24 patients when the studies were performed before cardiac catheterization and in 8 of 12 patients when performed during cardiac catheterization. The Doppler-derived estimates using the highest maximal velocity predicted catheterization pressure difference accurately when the measurements were not performed simultaneously (y = 1.05x - 3.3, r = 0.86, standard error of the estimate +/- 18.7 mm Hg) and the correlation was closer when the measurements were performed simultaneously (y = 1.09x - 2.7, r = 0.97, standard error of the estimate +/- 9.4 mm Hg). The transducer position that yielded the highest maximal velocity in an individual patient was the same before and after valvuloplasty. In all groups, the correlation with pressure at cardiac catheterization was improved by using the highest maximal velocity rather than the parasternal maximal velocity.