Pulmonary arterial hypertension (PAH) is a serious disease of the arteries connecting the lungs to the heart (the pulmonary arteries). As PAH develops, blood flow through the pulmonary arteries is restricted. The right side of the heart is put under increasing strain to pump blood through to the lungs, and this causes the right side of the heart to become enlarged. This process leads to the main symptoms of PAH – breathlessness, chest tightness, limited exercise capacity, and fatigue.

The early symptoms of PAH can be mild, and are common to many other conditions such as asthma, general fatigue, or lack of physical fitness. As the symptoms may be attributed to other causes, many patients with PAH are only finally diagnosed when the disease has already progressed beyond an early stage.

Untreated, PAH can reduce life expectancy. Treatment is aimed at improving symptoms, exercise tolerance, long-term outcomes and quality of life. Until the mid-1980s there were limited treatment options, and PAH was associated with a poor prognosis. Today, treatment options have significantly improved the outlook for patients with this condition.