Pathophysiology of PAH. The pulmonary vascular remodeling responsible for PAH is the consequence of closely intertwined predisposing and acquired factors. Thoses pathological elements affect all three layers of precapillary pulmonary arteries leading to intimal hyperplasia, medial thickening and adventitial remodeling/fibrosis. Intra- but also extra-pulmonary cells, such as inflammatory and progenitor cells, are suspected to play a role in this remodeling. This increases right ventricular afterload and consequently results in right ventricular failure.