Abstract :
Pulmonary hypertension is usually classified as primary (idiopathic) or secondary 1. In 2003, the World Health Organization revised the classification of PAH into 5 categories based in part on etiology: pulmonary arterial hypertension, pulmonary venous hypertension, pulmonary hypertension, pulmonary hypertension associated with hypoxemia, pulmonary hypertension resulting from chronic thrombotic or embolic disease, and miscellaneous. 2 Pulmonary arterial hypertension is defined as a sustained elevation of pulmonary arterial pressure to more than 25 mm Hg at rest or to more than 30 mm Hg with exercise, with a mean pulmonary – apillary wedge pressure and left ventricular end-diastolic pressure of less than 15 mm Hg. 3 Diagnosis of PPH one much excludes all secondary cause of PHT and demonstrates normal pulmonary wedge pressure. 2,3 Although pulmonary vascular resistance may be as high as 8-10 Wood units immediately after birth, it normally fall rapidly through the first week of life, by 6-8 weeks, pulmonary vascular resistance usually has reached a normal adult level of 1-3 Wood units. 2.3 pulmonary vascular disease with morphologic alterations of the pulmonary vasculature is one of the most serious complications of congenital heart disease. Once established, it is progressive and leads to premature death. Although the pathogenesis of most forms of pulmonary arterial hypertension is unknown, there have been many recent developments, especially pertaining to the molecular genetics and cell biology of idiopathic pulmonary arterial hypertension. The main vascular changes in pulmonary arterial hypertension are vasoconstriction, smooth-muscle cell and endothelial-cell proliferation, and thrombosis. In this review, we discuss these developments and relate them to other forms of pulmonary arterial hypertension.
