Pulmonary Artery Acceleration Time Provides a Reliable Estimate of Invasive Pulmonary Hemodynamics in Children

Abstract

Background Pulmonary artery acceleration time (PAAT) is a non-invasive method to assess pulmonary hemodynamics, but lacks validity in children. This study sought to evaluate the accuracy of Doppler echocardiography (DE) derived PAAT in predicting right heart catheterization (RHC) derived pulmonary arterial pressure (PAP), pulmonary vascular resistance (PVR) and compliance in children. Methods Prospectively acquired and retrospectively measured DE derived PAAT and RHC derived systolic PAP (sPAP), mean PAP (mPAP), index PVR (PVRi) and compliance were compared by regression analysis in a derivation cohort of 75 children (median age, 5.3 years; 1.3–12.6) with wide ranges of pulmonary hemodynamics. To account for heart rate variability, PAAT was adjusted for right ventricle ejection time (RVET) and corrected by the RR interval. Regression equations incorporating PAAT and PAAT:RVET from the derivation cohort were then evaluated for the accuracy of its predictive values for invasive pulmonary hemodynamics in a validation cohort of 50 age- and weight- matched children with elevated PAP and PVR. Results There were significant inverse correlations between PAAT and RHC derived mPAP (r = −0.82) and PVRi (r= −0.78) and direct correlation (r= 0.78) between PAAT and pulmonary compliance in the derivation cohort. For detection of pulmonary hypertension (PRVi > 3 WU x m2 and mPAP > 25 mmHg), PAAT < 90 msec and PAAT:RVET < 0.31 resulted in a sensitivity of 97% and a specificity of 95%. In the derivation cohort, the regression equations relating PAAT with mPAP and PVRi were: mPAP = 48 – 0.28 x PAAT and PVRi = 9 –0.07 x PAAT. These PAAT integrated equations predicted RHC measured pulmonary hemodynamics in the validation cohort with good correlations (r = 0.88, 0.83 respectively), small biases (<10%), and minimal coefficient of variation (<8%). Conclusions PAAT inversely correlates with RHC measured pulmonary hemodynamics and directly correlates with pulmonary arterial compliance in children. The study established PAAT based regression equations in children to accurately predict RHC derived PAP and PVR.

Derivation and Validation of Formula relating Pulmonary Acceleration Time and Mean Pulmonary Artery Pressure in Indian Population

“…In the ROC curve analysis, the cutoff values of PAT and HRcPAT to detect PAH (MPAP < 25 mm Hg) were 74 and 99 ms with a sensitivity and specificity of 93/100% and 100/100% respectively. The cutoff of PAT value to detect PAH in this study is comparatively lesser, whereas the HRcPAT cutoff was very similar to that described in other studies like 100 ms by Dabestani et al, 34 100 ms by Granstem et al, 37 90 ms by Levy et al 25 in Western population. Even though the PAT cutoff is lesser than the previously described values in Western population, it predicts PAH in the Indian population with better sensitivity and specificity, suggesting the use of this lesser cutoff of PAT value or use of HRcPAT to define PAH in Indian population.…”

“…Further in the subgroup analysis, MPAP in patients with severe PAH (MPAP ≥ 50 mm Hg) showed a better correlation (r 2 = 0.433) with PAT than in patients with less than severe PAH (r 2 = 0.260). As shown by Levy et al 25 and Kitabatake et al, 38 PAT is better in estimating MPAP in patients with severe PAH than in patients with less than severe PAH. Similarly, PAT also showed a good correlation (r 2 = 0.6193) with PVRI measured invasively and the regression equation derived (PVRI = 14.9 − 0.09 PAT) in the derivation cohort showed good correlation with the PVRI derived invasively and from the formula given by Levy et al 25 (PVRI = 9 − 0.07 PAT) with minimal bias (<10%),…”

“…The earlier studies did not take into account the influence of HR in the study and suggested the HR correction in upcoming studies, which has been followed in our study, which showed HR has an influence on PAT-based measurement of MPAP. Even though the recent study by Levy et al 25 in children included RV function parameters like RV strain and RVET, patients with shunt lesion are included in that study, which is known to affect the duration of RVET, which, in turn, affects PAT. These limitations have been eliminated by including only patients with no shunt lesions and RVOTO.…”

“…To eliminate this confounding factor, Levy et al 25 in their study of 75 pediatric patients used the parameter PAT/ RVET and found that PAAT/RVET < 0.30 had sensitivity of 96% and specificity of 95%, with an area under the curve of 0.92 of predicting patients with PAH (MPAP > 25 mm Hg), whereas, in this study, the PAAT/RVET had poor correlation with the measured MPAP, raising doubt on the reliability of this parameter in measuring MPAP.…”

Normal Reference Values and z Scores of the Pulmonary Artery Acceleration Time in Children and Its Importance for the Assessment of Pulmonary Hypertension

“…In children, PVR and mPAP were shown to have high associations with PAAT. 32 If these parameters may explain a substantial amount of the remaining variance cannot be answered within this study.…”