NEJM article

Pulmonary hypertension is a syndrome characterized by marked remodeling of the pulmonary vasculature and a progressive rise in the pulmonary vascular load, leading to hypertrophy and remodeling of the right ventricle. Death results from right ventricular failure if pulmonary hypertension is left untreated. Pulmonary hypertension is currently defined hemodynamically by a mean pulmonary arterial pressure of higher than 20 mm Hg at rest, as measured by right heart catheterization.1 Precapillary pulmonary hypertension due to pulmonary vascular disease is further defined by an elevation in pulmonary vascular resistance of at least 3 Wood units (WU), in contrast to isolated postcapillary pulmonary hypertension, in which the pulmonary vascular resistance is less than 3 WU and the elevation in the mean pulmonary arterial pressure is due to elevated filling pressures on the left side of the heart.