Pulmonary hypertension is a type of high blood pressure that affects the arteries in your lungs and the right side of your heart.
The heart has two upper chambers (atria) and two lower chambers (ventricles). Each time blood passes through the heart, the lower right chamber (right ventricle) pumps blood to lungs through a large blood vessel (pulmonary artery).
These changes in the pulmonary arteries can reduce or block blood flow through the blood vessels. This makes it harder for blood to flow, raising the blood pressure in the pulmonary arteries.
This hole in the heart causes blood to circulate abnormally in your heart. Oxygen-carrying blood (red blood) mixes with oxygen-poor blood (blue blood). The blood then returns to the lungs instead of going to the rest of the body, increasing the pressure in the pulmonary arteries and causing pulmonary hypertension.