The right side of the heart pumps blood through the lungs, where it picks up oxygen. Blood returns to the left side of the heart, where it is pumped to the rest of the body.
When the small arteries (blood vessels) of the lung become narrowed, they cannot carry as much blood. When this happens, pressure builds up. This is called pulmonary hypertension.
The heart needs to work harder to force the blood through the vessels against this pressure. Over time, this causes the right side of the heart to become larger. This condition is called right-sided heart failure, or cor pulmonale.
Pulmonary hypertension may be caused by:
- Autoimmune diseases that damage the lungs, such as scleroderma and rheumatoid arthritis
- Birth defects of the heart
- Blood clots in the lung (pulmonary embolism)
- Heart failure
- Heart valve disease
- HIV infection
- Low oxygen levels in the blood for a long time (chronic)
- Lung disease, such as COPD or pulmonary fibrosis
- Medicines (for example, certain diet drugs)
- Obstructive sleep apnea
In many patients, the cause of pulmonary hypertension is unknown. In this case, the condition is called idiopathic pulmonary arterial hypertension (IPAH). Idiopathic means the cause of a disease is not known. IPAH is rare. It affects more women than men.
If pulmonary hypertension is caused by a known medicine or medical condition, it is called secondary pulmonary hypertension.