Friesen RM, et al. - Researchers assessed the main pulmonary artery (MPA) stiffness in children with pulmonary arterial hypertension (PAH) in this first-ever comprehensive evaluation exploring the mechanistic link between flow hemodynamics and MPA stiffness and the prognostic ability of these measures regarding clinical outcomes. In these subjects, a major contribution of MPA stiffness to right ventricular (RV) dysfunction was found as children with PAH. Prediction of moderate clinical outcomes was possible by pulse wave velocity, which was suggested to be a possible useful predictive marker of disease activity in children with PAH.