Abstract Details

Presented By: Barker, Alex
Affiliated with: University of Colorado, Boulder, Department of Mechanical Engineering
Authors: Alex J. Barker (1), Craig Lanning (2 3), Dunbar Ivy (3), Kendall Hunter (2 3), Robin Shandas (1 2 3)
From: (1) Dept of Mechanical Engineering – University of Colorado at Boulder, (2) Center for Bioengineering – University of Colorado at Denver and Health Science Center Aurora, (3) Dept. of Pediatrics Division of Cardiology – The Children’s Hospital Denver
Title
Artery Dilatation in Pediatric Pulmonary Hypertension Patients: Functional Implications and Outcomes
Abstract

Introduction: Using phase contrast magnetic resonance imaging (PC-MRI), our group has previously reported blood flow and morphology characteristics in the RPA of pediatric pulmonary arterial hypertension (PAH) patients. One striking difference between control and PAH patients is rate of dilatation in the right pulmonary artery (RPA). Since artery size plays a large role in the determination of wall shear stress (WSS) – and since WSS is reported to regulate transcriptional events, this study aims to quantify the affect of abnormal RPA sizes on WSS and morbidity outcomes.

Methods: The parameters affecting WSS are: artery morphology, compliance, flow, and pulsatility. Thus, the RPA size, distension, flow waveform, and circumferentially averaged systolic WSS were measured in 10 control and 11 PAH (MPAP>25 mmHg or PVR>5 Woods units) patients using PC-MRI. ANCOVA analysis of the data as a function of age and body surface area (BSA) were performed. Color M-Mode Tissue Doppler Imaging of additional patients was used to augment the analysis of artery size with age and BSA (combined numbers, n=34 PAHs and n=23 controls). A cumulative logistic regression was performed on World Health Organization (WHO) functional assessment scores to predict the significance of RPA size to patient outcome.

Results: Linear regression analysis of the combined MR and echo data of pediatric patients found that age was best correlated to RPA size (PAH: r=0.81, P<0.001; Control: r=0.83, P<0.001). The rate of PAH dilatation was 250% the rate of the controls and significantly different (0.81 vs. 0.33 mm/year, P<0.001). Peak systolic flow was found to be correlated to age for both MR populations (P<0.001) but no differences as a function of age existed between populations (P=0.55). WSS was found to decrease significantly with age in the MR PAH population (P=0.02) while no correlation was found in the controls (P=0.41). Logistic regression predicted a 76% percent chance of WHO score worsening with an RPA diameter greater than 2 cm.

Conclusions: Pulmonary artery dilation occurs at a significantly faster rate in PAH patients versus controls, while systolic flow does not vary between populations. The consequence of maintaining equal flow through a larger artery is a decrease in WSS. Artery size and WHO functional score are correlated.