Pulmonary arterial hypertension

Pulmonary arterial hypertension, abbreviated PAH, is a syndrome in which the blood pressure in the pulmonary arteries and arterioles of the lungs is raised. Diagnosis requires a right heart catheterization showing a mean pulmonary artery pressure above 20 mmHg, a pulmonary vascular resistance above 3 Wood units, and a wedge pressure below 15 mmHg, which excludes pressure raised beyond the capillary bed. It is the first World Health Organization group within the wider category of pulmonary hypertension and is subdivided by cause, including idiopathic, heritable, drug and toxin induced forms. Early symptoms are breathlessness, fatigue, lightheadedness and chest pain, and untreated disease leads to right heart failure. Targeted drug therapies have improved survival since the 1980s, and an atrial septostomy or lung transplantation is used when drugs fail.