Pulmonary hypertension is currently classified into the following categories: 1. Arterial pulmonary hypertension (idiopathic, familial, caused by diseases related to connective tissue disease and shunt congenital heart disease, caused by pulmonary venous or capillary lesions, persistent pulmonary hypertension in newborns) 2.Pulmonary venous hypertension (usually caused by left heart disease and valvular disease). 3.Pulmonary hypertension caused by respiratory disease and hypoxia. 4.Pulmonary hypertension caused by chronic thrombosis and embolism. 5.Mixed pulmonary hypertension.