To understand pulmonary hypertension, it is helpful to understand the job of the heart and lungs, and the flow of blood.
As your heart beats, it sends blood throughout the body. The tissues of the body need oxygen from the blood to function properly. After the tissues use oxygen from the blood, they send oxygen-poor blood to the right side of the heart. Then, the heart pumps oxygen-poor blood through the pulmonary arteries to the lungs so the lungs can add oxygen to the blood. The force (pressure) of the blood against the walls of the pulmonary arteries is called the pulmonary pressure.
When this pressure gets too high, the pulmonary arteries become narrow or blocked. This makes the blood not flow as well, so the heart has to work harder to maintain blood flow into the lungs. Over time, this can cause damage to the heart and lungs.
