Is noninvasive determination of pulmonary artery pressure feasible using deceleration phase doppler flow velocity characteristics in mechanically ventilated children with congenital heart disease?

Abstract

Noninvasive determination of pulmonary hemodynamics is important for the management of congenital heart disease complicated by pulmonary hypertension. Flow deceleration is less influenced by right ventricular function and would allow more accurate estimation of pulmonary hemodynamics than acceleration. Respiratory influences on pulmonary blood flow are exaggerated by mechanical ventilation. Doppler-derived pulmonary artery (PA) blood flow velocity characteristics were therefore compared with pulmonary hemodynamic parameters in 42 mechanically ventilated children, aged 0.2 to 14.8 years (mean ± SD 6.7 ± 4.9). Mean PA pressure ranged from 11 to 47 mm Hg (21 ± 9 mm Hg). Pulmonary hypertension was present in 14 patients. Significant differences were found between patients with and without pulmonary hypertension in maximal velocity (1.03 ± 0.22 vs 0.88 ± 0.18 m/s), acceleration time (119 ± 39 vs 136 ± 29 ms), maximal acceleration (17.6 ± 6.4 vs 13.1 ± 4.0 m/s 2), mean acceleration (9.3 ± 2.6 vs 6.7 ± 2.0 m/s 2), and mean deceleration (4.5 ± 1.0 vs 3.8 ± 0.8 m/s 2). In contrast to our hypothesis of the deceleration phase-derived parameters, only maximal deceleration correlated with PA pressure. Acceleration parameters showed closer relations with PA pressures, but correlations were generally low and did not permit accurate prediction of PA pressure (SEE 5 to 11 mm Hg), PA resistance (SEE 1.14 U · m 2) or PA driving force (SEE 7 mm Hg). An analysis that took respiratory phase into account did not improve correlations. Measurement of mean acceleration, maximal deceleration, and rate-corrected preejection period permitted for accurate discrimination between the presence or absence of pulmonary hypertension, with positive and negative predictive values being 92% and 90%. In mechanically ventilated children with congenital heart disease, accurate noninvasive PA pressure assessment is not possible. Accurate predictions for the presence of pulmonary hypertension can be made by measurement of both acceleration and deceleration parameters.