Differences in pulmonary arterial flow hemodynamics between children and adults with pulmonary arterial hypertension as assessed by 4D-flow CMR studies

Despite different developmental and pathological processes affecting lung vascular remodeling in both patient populations, differences in 4D MRI findings between children and adults with PAH have not been studied. The purpose of this study was to compare flow hemodynamic state, including flow-mediated shear forces, between pediatric and adult patients with PAH matched by severity of pulmonary vascular resistance index (PVRi). Adults ( n = 10) and children ( n = 10) with PAH matched by pulmonary vascular resistance index (PVRi) and healthy adult ( n = 10) and pediatric ( n = 10) subjects underwent comprehensive 4D-flow MRI to assess peak systolic wall shear stress (WSS max ) measured in the main (MPA), right (RPA), and left pulmonary arteries (LPA), viscous energy loss (E L ) along the MPA-RPA and MPA-LPA tract, and qualitative analysis of secondary flow hemodynamics. WSS max was decreased in all pulmonary vessels in children with PAH when compared with the same age group (all P < 0.05). Similarly, WSS max was decreased in all pulmonary vessels in adult PAH patients when compared with healthy adult subjects (all P < 0.01). Average E L was increased in adult patients with PAH when compared with the same age group along both MPA-RPA ( P = 0.020) and MPA-LPA ( P = 0.025) tracts. There were no differences in E L indices between adults and pediatric patients. Children and adult patients with PAH have decreased shear hemodynamic forces. However, pathological flow hemodynamic formations appear to be more consistent in adult patients, whereas flow hemodynamic abnormalities appear to be more variable in children with PAH for comparable severity of PVRi. NEW & NOTEWORTHY Both children and adult patients with PAH have decreased shear hemodynamic forces inside the pulmonary arteries associated with the degree of vessel dilation and stiffness. These differences also exist between healthy normotensive children and adults. However, pathological flow hemodynamic formations appear to more uniform in adult patients, whereas in children with PAH flow, hemodynamic abnormalities appear to be more variable. Pathological flow formations appear not to have a major effect on viscous energy loss associated with the flow conduction through proximal pulmonary arteries.