Abstract 4387: Artery Dilatation in Pediatric Pulmonary Hypertension Patients Decreases Hemodynamic Wall Shear Stress
Wall shear stress (WSS) is reported to regulate transcriptional events in vascular remodeling. Using PC-MRI, our group has found that pediatric PAH patients exhibit a progressive decrease in RPA WSS with age compared to controls. This study aims to quantify the pathology responsible for abnormally low WSS measurements in PAH patients. 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 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, n=34 PAHs and n=23 controls). Regression analysis of the combined MR and echo data 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). 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.