The main effect of pulmonary hypertension is that it causes the right ventricle to work harder to pump blood to the lungs. Because the right ventricle is working harder, it gets bigger and thicker, and it could fail.
Pulmonary hypertension can have many causes or associated diseases.
In children, one of the most common causes is congenital heart disease. Some heart defects can cause pulmonary hypertension because they direct more blood than normal to the pulmonary artery. This is one reason it can be important to repair heart defects, when possible, before the heart or blood vessels are damaged permanently. Often, but not always, pulmonary hypertension will improve after the congenital heart defect is repaired.
Another common cause of pulmonary hypertension in children is lung disease. Lung disease may occur because a baby was born early (prematurely) or they have a congenital lung problem. Children can also get lung disease after being on a machine to help them breathe (mechanical ventilator) for a long time. Sometimes, children with obstructive sleep apnea can develop pulmonary hypertension.
Rarely, the cause of pulmonary hypertension is not known, and then we call it idiopathic. In some cases, there is a family history of the condition.