What is (are) Pulmonary Hypertension ? 
 Pulmonary hypertension (PULL-mun-ary HI-per-TEN-shun), or PH, is increased pressure in the pulmonary arteries. These arteries carry blood from your heart to your lungs to pick up oxygen.
                
PH causes symptoms such as shortness of breath during routine activity (for example, climbing two flights of stairs), tiredness, chest pain, and a racing heartbeat. As the condition worsens, its symptoms may limit all physical activity.
                
Overview
                
To understand PH, it helps to understand how your heart and lungs work. Your heart has two sides, separated by an inner wall called the septum.
                
Each side of your heart has an upper and lower chamber. The lower right chamber of your heart, the right ventricle (VEN-trih-kul), pumps blood to your pulmonary arteries. The blood then travels to your lungs, where it picks up oxygen.
                
The upper left chamber of your heart, the left atrium (AY-tree-um), receives the oxygen-rich blood from your lungs. The blood is then pumped into the lower left chamber of your heart, the left ventricle. From the left ventricle, the blood is pumped to the rest of your body through an artery called the aorta.
                
For more information about the heart and lungs, go to the Diseases and Conditions Index How the Heart Works and How the Lungs Work articles.
                
PH begins with inflammation and changes in the cells that line your pulmonary arteries. Other factors also can affect the pulmonary arteries and cause PH. For example, the condition may develop if:
                
The walls of the arteries tighten.
                
The walls of the arteries are stiff at birth or become stiff from an overgrowth of cells.
                
Blood clots form in the arteries.
                
These changes make it hard for your heart to push blood through your pulmonary arteries and into your lungs. As a result, the pressure in your arteries rises. Also, because your heart is working harder than normal, your right ventricle becomes strained and weak.
                
Your heart may become so weak that it can't pump enough blood to your lungs. This causes heart failure. Heart failure is the most common cause of death in people who have PH.
                
PH is divided into five groups based on its causes. In all groups, the average pressure in the pulmonary arteries is higher than 25 mmHg at rest or 30 mmHg during physical activity. The pressure in normal pulmonary arteries is 820 mmHg at rest. (The mmHg is millimeters of mercurythe units used to measure blood pressure.)
                
Other diseases or conditions, such as heart and lung diseases or blood clots, usually cause PH. Some people inherit the condition (that is, their parents pass the genes for PH on to them). In some cases, the cause isn't known.
                
Outlook
                
PH has no cure. However, research for new treatments is ongoing. The earlier PH is treated, the easier it is to control.
                
Treatments include medicines, procedures, and other therapies. These treatments can relieve PH symptoms and slow the progress of the disease. Lifestyle changes also can help control symptoms.