pulmonary hypertension

The lungs normally run on a low-pressure circuit. Unlike the high-pressure system that pushes blood around the body, the pulmonary arteries are designed to carry blood gently through delicate lung tissue. Pulmonary hypertension is when the pressure in these arteries rises abnormally high, forcing the right side of the heart to work like a pump labouring against a clogged hose.

The condition is defined by an elevated mean pulmonary artery pressure measured during right heart catheterization. It is not a single disease but a final common state reached by many different paths: disease of the small lung vessels themselves, left-sided heart failure backing pressure up into the lungs, chronic lung diseases and low oxygen, old unresolved blood clots, and various other causes. These are grouped into clinical categories that guide very different treatments.

Because the early symptoms, breathlessness on exertion and fatigue, are vague and common, pulmonary hypertension is often recognised late. Over time the strained right ventricle can enlarge and ultimately fail, a state called cor pulmonale. Identifying the underlying group matters greatly, since the specific drugs that help one form can be useless or harmful in another.