Types of PH

Group 1: Pulmonary Arterial Hypertension (PAH)
Although PAH is what most people think of when they hear about PH, it only represents ~3% of all types of PH. In PAH, the primary problem is narrowed and stiff arteries in the lungs, which increases the blood pressure and stresses the right side of the heart. PAH can occur without a clear cause (idiopathic), be inherited, or be related to other conditions or diseases. There are several drugs that can cause PAH in adults, the most notorious being methamphetamines and diet/weight-loss pills (e.g. Fen-Phen). PAH can also develop in association with HIV, connective tissue disease (especially scleroderma), liver disease, congenital (at birth) heart disease, and schistosomiasis (a parasitic infection occurring in tropical areas). PAH can be treated with pulmonary vasodilators to relax and open the arteries in the lungs and other therapies. Treating any associated disease and stopping any potentially harmful drugs is essential.

Group 2: Pulmonary Hypertension Due to Left Heart Disease
Group 2 pulmonary hypertension is by far the most common type of PH, representing >60% of all cases. In this group, the left side of the heart (which receives blood from the arteries in the lungs) does not work as efficiently as it should because of any of the following: 1. The left-sided heart chamber does not pump normally (commonly referred to as "heart failure"), 2. The left-sided heart chamber does not relax and fill normally due to stiffened muscles (referred to as "diastolic dysfunction"), or 3. The valves that allow blood to flow between the chambers of the heart are either too "leaky" or too "tight." All of these issues can cause back-pressure from the left side of the heart into the arteries in the lungs. Group 2 pulmonary hypertension should not be treated with medications used for PAH, since they can actually worsen the condition; instead, treatment focuses on improving the function of the left heart and/or abnormal valves.

Group 3: Pulmonary Hypertension Due to Lung Disease
Group 3 pulmonary hypertension is another more common type of PH. It is caused by underlying lung disease and/or prolonged low levels of oxygen in the blood. Most common causes of group 3 PH are associated with chronic obstructive lung disease (e.g., COPD), restrictive lung diseases causing scarring of the tissue between the lung's air sacs (e.g., interstitial lung disease/pulmonary fibrosis), and sleep disorders, most commonly sleep apnea. In children, common types of group 3 PH include developmental lung disorders like bronchopulmonary dysplasia and congenital diaphragmatic hernia. Low oxygen levels in your lungs and blood, either due to these diseases or from living at high altitude, causes the arteries in your lungs to constrict, increasing the pressure and limiting blood flow. Treatment mostly relies on treating the underlying lung disease, sleep disorder and correcting low oxygen levels by wearing supplemental oxygen as prescribed by your doctor. Recently an inhaled pulmonary vasodilator medication that relaxes arteries allowing for increased blood flow was approved for treatment of pulmonary hypertension due to interstitial lung disease in adults. A key strategy for managing this group of patients in children is to optimize lung function and ventilation as able. We are always wanting to aim for "happy lungs."

Group 4: Pulmonary Hypertension Due to Chronic Blood Clots in the Lungs
Group 4 pulmonary hypertension occurs when the lung arteries are blocked, most commonly chronic thromboembolic pulmonary hypertension (CTEPH) caused by blood clots in the lung that never dissolved. Many people are not aware of ever having blood clots in the lungs which is why it’s crucial to have specific testing done to rule out this type of pulmonary hypertension. Old undissolved blood clots in the arteries in the lungs form scar tissue blocking blood flow, raising the pressure, and straining the right side of the heart. The gold standard for treating and possibly curing CTEPH is to undergo highly specialized surgery done at expert centers to remove the old blood clots from the lungs. Other treatments include balloon pulmonary angioplasty (BPA) to open blocked blood vessels and a specific medication approved for patients in whom surgery is not an option or still have some level of PH after surgery.

Group 5: Miscellaneous
This group includes other diseases and conditions associated with PH (such as sarcoidosis, sickle cell anemia, removal of the spleen and certain metabolic conditions) that are not well-understood, nor are there specific treatment options. In children, this group may include patients with complicated heart disease associated with abnormalities of the pulmonary vessels.