High pressure. Pulmonary hypertension is a rise the pressure readings in the pulmonary vascular bed. It can be estimated using a study called a cardiac ultrasound/echocardiogram. Many patients then go on to a more definitive evaluation of the pressure with a procedure called a heart catheterization (direct measurement of the pressures). High pressure can cause fainting, chest pain and edema (swelling).
Lung vessel damage. Phtn is a generic name for high pressures in the blood vessels of the lung. Pah is narrowing of the pulmonary arteries which cause the right side of the heart to pump harder and increase the blood pressure, to allow blood to flow through the blood vessels of the lung. There are other forms of phtn, but pah is the must dangerous.