The term pulmonary hypertension (PH) refers to high blood pressure in the arteries in the lungs which puts stress on the right side of the heart. It is important to remember that PH can occur for a variety of reasons and can affect people across the lifespan, from infancy to adulthood. Experts divide PH into 5 ‘groups’, each representing a broad category of causes of PH.
Because PH is so complex and no two patients are alike, it is essential to determine which group you or your child belongs to by an expert team that specializes in PH. This will determine how your PH is treated with medicine and other therapies. The ultimate goal is to identify and address the root cause of the individual's PH.
The classification of PH is based upon the “mechanism” of developing high blood pressure in the lungs. Therefore, treatment for one type may not work for the other or may even make the disease worse. In the real world, some patients may have more than one type of PH often referred to as “mixed” disease.
Group 1: Pulmonary Arterial Hypertension (PAH) Although PAH is what most people think of when they hear about PH, it only accounts for ~3% of all PH worldwide. In PAH, the primary problem is narrowed,stiff lung arteries that increase the blood pressure and stress the right side of the heart. PAH can occur without a clear cause (idiopathic), be due to genetic mutations (heritable), or be related to other conditions or diseases. Several drugs are associated with PAH in adults, the most common being methamphetamine and diet 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). There are a number of medications approved to treat PAH. PAH therapies work by relaxing and slowing the thickening of the lung arteries. New medications for PAH are under investigation in clinical trials, and some have recently been approved for use. Treating any associated disease and stopping any potentially harmful drugs are essential to the successful management of PAH.
Group 2: Pulmonary Hypertension Due to Left Heart Disease Group 2 PH is by far the most common type, 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 HFpEF - heart failure with preserved ejection fraction); or 3. The valves that allow blood to flow between the heart chambers are either too "leaky" or too "tight."
All of these issues can cause back pressure from the left side of the heart into the lung arteries. In general, Group 2 PH should not be treated with medications used for PAH, because these medicines 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 PH is also a common type of PH. It is caused by disease of the lung tissues and/or prolonged exposure to low levels of oxygen in the blood. The most common causes of group 3 PH are diseases of the airways in the lungs (e.g., COPD/emphysema), scarring of the tissue between the lung air sacs ((e.g., interstitial lung disease/pulmonary fibrosis), and abnormal breathing with sleep (e.g., 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 altitudes, cause the arteries in your lungs to constrict, increasing the pressure and limiting blood flow. Management of Group 3 PH in children and adults focuses on treating any underlying lung disease or sleep breathing disorder and correcting low oxygen levels by wearing oxygen (as prescribed by a doctor). There is an inhaled PH medication that was approved for the treatment of PH due to interstitial lung disease in adults. Clinical trials are underway exploring other medications in Group 3 PH.
Group 4: Pulmonary Hypertension Due to Chronic Pulmonary Artery Obstruction Group 4 PH occurs when the lung arteries are blocked, most commonly by chronic blood clots (chronic thromboembolic pulmonary hypertension, CTEPH). In CTEPH, 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. Approximately 25% of people diagnosed with CTEPH have no known history of blood clots in the lungs, which is why it is crucial to rule it out with special testing at the time of PH diagnosis. The gold standard treatment for CTEPH is a highly specialized surgery performed at expert centers to remove the old blood clots from the lungs. In some cases, removing the clots can be curative. 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 who 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 includes patients with complicated heart disease associated with abnormalities of the pulmonary vessels.
This information is intended for educational purposes only and not to be used to change or direct medical care. This information should not replace direction by your treating care team and all medical management should be directed by your PH treating physician and your care team.
