Pulmonary hypertension is characterized by high blood pressure (hypertension) in the blood vessels that supply oxygen-poor blood to the lungs. There are two forms of pulmonary hypertension: primary and secondary. Primary pulmonary hypertension  (PPH) has no known cause and is relatively uncommon. It is sometimes called idiopathic pulmonary hypertension. Secondary pulmonary hypertension (SPH) is caused by an underlying heart condition, lung disease or pulmonary embolism (a blood clot that has become lodged in one or more of the pulmonary blood vessels). Secondary pulmonary hypertension has also been associated with the use of certain diet drugs, cocaine abuse and HIV infection.

Like all forms of high blood pressure, pulmonary hypertension requires treatment to reduce the risk of serious consequences. These consequences can include a leaking valve on the right side of the heart (tricuspid regurgitation) or complete right-side heart failure. In many cases pulmonary hypertension is not detected until after a diagnosis of right-sided heart failure.

Treatment for pulmonary hypertension includes lifestyle changes, medication and, in extreme cases, surgery.