PULMONARY VASCULAR REMODELING IN PULMONARY-HYPERTENSION

Pulmonary vascular remodelling is different in pulmonary hypertension associated with chronic alveolar hypoxia and in that associated with the formation of plexiform lesions. In the case of hypoxia the remodelling is the same in native highlanders and in patients with chronic obstructive lung disease. In plexogenic pulmonary arteriopathy the remodelling is the same irrespective of whether the underlying cause is a congenital cardiac septal defect. or primary pulmonary hypertension. In chronic hypoxia the remodelling takes the form of muscularization of pulmonary arterioles, and the limited migration of vascular smooth muscle cells from the media into the intima where the adult myocytes assume a longitudinal orientation. A formation of in inner muscular tube internal to the longitudinal muscle occurs. In plexogenic pulmonary arteriopathy there is also migration of smooth muscle inwards from the media but in this case the myocytes are altered being electron-dense and having a smooth outline. In this form of remodelling there is extensive infiltration of the intima by these cells which become transformed into myofibroblasts which enter and block the vascular lumen leading to an elevation of pulmonary vascular resistance.