PH, or Pulmonary Hypertension, is continuous high blood pressure in the pulmonary artery. PH is a serious condition for which there are treatments but no cure. In PH, the muscles within the walls of the arteries may tighten up. The inside of the arteries narrow, and may thicken as the amount of muscle increases in some arteries.
Scar tissue may form in the walls of arteries. As the walls thicken and scar, the arteries become increasingly narrow. Tiny blood clots may form within the smaller arteries, causing blockages, thus less room for the blood to flow through these narrower arteries. The arteries may also stiffen.
Over time, some of the arteries may become completely blocked. The narrowing of the pulmonary arteries causes the right side of heart to work harder to pump blood through the lungs. Over time, the heart muscle weakens and loses its ability to pump enough blood for the body's needs. About 300 new cases of PH are diagnosed in the United States each year.