Glossary of pulmonary and PAH-related terms 6-minute walk distance (6MWD): The 6-minute walk test (6MWT) is performed by healthcare professionals to see how far a person can walk in 6 minutes. This distance (6MWD) is used to measure patients' ability to exercise. By repeating the 6MWD at each visit, doctors can monitor changes in patients’ ability to exercise over time. Arterial: Relating to arteries—the tubelike blood vessels that carry blood from the heart. Associated PAH (APAH): PAH that exists when another condition, such as connective tissue disease or HIV infection, is present. Blood pressure: The pressure exerted by the blood upon the walls of the blood vessels—especially arteries. Cardiovascular: Related to the circulatory system comprising the heart and blood vessels. Clinical Classification of PH: System used to classify pulmonary hypertension (PH) based on its causes and its clinical features. There are five main classifications of PH. The first, Group 1, is pulmonary arterial hypertension (PAH). There are 5 subgroups of Group 1 PAH, which include: Idiopathic Heritable Drug- and toxin-induced Associated with other diseases, such as connective tissue diseases, HIV, congenital heart disease Persistent pulmonary hypertension of the newborn Connective tissue disease: A group of diseases characterized by inflammatory or degenerative changes in connective tissue. Examples include scleroderma, systemic lupus erythematosus (SLE), and rheumatoid arthritis. Endothelin receptor antagonist (ETRA): Class of medication used in PAH. Available in oral form. Bosentan and ambrisentan are ETRAs. Etiology: The cause of a disease or abnormal condition. Idiopathic: Arising spontaneously or without an identifiable cause. Idiopathic PAH (IPAH): A type of PAH in which there is neither a family history of PAH nor an identified risk factor. Intravenous infusion: An infusion, usually of a drug, administered by entering a vein. Lung Biotechnology: A healthcare company committed to serving the needs of the PAH community, as well as patients with other rare forms of life-threatening pulmonary diseases. NYHA Functional Class: Scale developed by the New York Heart Association (NYHA) and used in a slightly modified form by doctors to help describe the severity of PAH, and the type of treatment each patient may need. Orphan disease: A term used for a disease that is rare. The US Food and Drug Administration defines an orphan disease as one that affects fewer than 200,000 people nationwide. PAH is considered to be an orphan disease. Phosphodiesterase type 5 (PDE-5) inhibitor: Class of medication used to treat PAH. Available in oral (pill) form. Tadalafil and sildenafil are PDE-5 inhibitors. Prostacyclin: A naturally occurring substance that helps keep blood vessels dilated (open) and working properly. In patients with PAH, prostacyclin levels may be reduced. Prostacyclin analogues: The first class of medicines approved to treat PAH. Help replace some of the activity of prostacyclin in the body. Available in 2 forms: inhaled (breathed into the lungs) and infused (injected into a vein or under the skin). Pulmonary: Relating to the lungs. Pulmonary arterial hypertension (PAH): High pressure in the arteries of the lungs. PAH is different from general hypertension, a disease that involves high blood pressure in other areas of the body. Pulmonary function tests: A group of tests that measure how well the lungs take in and release air and how well they move gases such as oxygen from the atmosphere into the body's circulation. Scleroderma: A slowly progressive disease in which connective tissue (collagen) deposits in the skin, internal organs, and joints, resulting in thickening these structures. United Therapeutics: Lung Biotechnology's parent company. Vasodilatation: Widening of blood vessels resulting from relaxation of the muscular wall of the vessels.