DefinitionPulmonary hypertension is abnormally high blood pressure in the arteries of the lungs. It makes the right side of the heart need to work harder than normal.Alternative NamesPulmonary arterial hypertension; Sporadic primary pulmonary hypertension; Familial primary pulmonary hypertension; Idiopathic pulmonary arterial hypertension; Primary pulmonary hypertension; PPH; Secondary pulmonary hypertensionCauses, incidence, and risk factorsThe right side of the heart pumps blood through the lungs, where it can receive oxygen.When the small arteries (blood vessels) of the lung become narrowed, they cannot carry as much blood. When this happens, pressure builds up. This is called pulmonary hypertension.The heart needs to work harder to force the blood through the vessels against this press