Definition of Pulmonary hypertension:

Pulmonary hypertension is abnormally high blood pressure in the arteries of the lungs. It makes the right side of the heart need to work harder than normal.

Causes, incidence, and risk factors:

The right side of the heart pumps blood through the lungs, where it picks up oxygen. Then, the blood returns to the left side of the heart, where it is pumped to the whole 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. Not enough blood flows to the lungs to pick up oxygen.

At this point, heart failure involves the right side of the heart. This is called 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)
• Congestive 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 cases the cause is unknown. In this case, the condition is called idiopathic pulmonary arterial hypertension (IPAH). It used to be called primary pulmonary hypertension (PPH).

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.