The WHO grouped pulmonary hypertension in the year 1973. Initially, it was grouped into two: primary and secondary form of pulmonary hypertension. If the cause of the disease is known is referred as primary pulmonary hypertension and if unknown, it is referred to as secondary and sometimes it is denoted as idiopathic pulmonary hypertension.
What is The WHO Classification of Pulmonary Hypertension?
But today, the WHO classification of pulmonary hypertension extended to 5 groups, to highlight the significance of the fundamental cause of the disease. Every few years the experts in the field of pulmonary hypertension meet and update the guidelines with regard to diagnosing and treating pulmonary hypertension. This classification helps to fight the disease and used for several purposes, particularly by the researchers, nurse, and physicians for treating the patients.
The main five groups are classified according to European Society of Cardiology (ESC) and European Respiratory Society (ERS) are delineated below:
- WHO Group I – Pulmonary Arterial Hypertension
- WHO Group II- Pulmonary Hypertension in relation with left heart disease
- WHO Group III- Pulmonary Hypertension in relation with lung disease.
- WHO Group IV- Pulmonary Hypertension associated with blood clots in the lung.
- WHO Group V- Pulmonary Hypertension associated with blood and other rare disorders
Group I – Pulmonary Arterial Hypertension
Group I is associated with narrowing of lung blood vessels. The cause of the disease is unknown hence it is referred to as idiopathic. This is a serious genetic disorder that may pass to offspring. Certain drugs and diseases like immunocompromised condition (HIV infection), cardiac problems, high BP, sickle cell anemia, parasite infection, and connective tissue disorder can able to cause pulmonary hypertension. Sometimes rare disorders like pulmonary capillary hemangiomatosis and persistent pulmonary hypertension of newborns also can be responsible for the group I. They do not respond to treatment and organ transplantation is the best choice.
Group II – Pulmonary Hypertension Resulting From Left Heart Dysfunction
Group II is a chronic form of disease associated with a left side of the heart. Some of the changes include:
- Change in the function of LV systolic i.e. heart cells unable to pump blood successfully
- Change in the function of LV diastolic – It refers to the heart cells unable to permit enough blood to flow inside.
- Change in the function of valve– It is a disease referred to as “leaky valve”, characterized by damage to the left valves of the heart.
- Congenital Heart Disease (CHD).
- Group II patients particularly, the valvular disease often treated by surgery and replacement of the valve is required.
Group III – Pulmonary Hypertension in Relation to Lung Disease
Group 3 is the consequences of several lung diseases. Sometimes shortage of oxygen in the body (chronic hypoxia) also triggers this group. Treatment for group III patients is targeted on improving lung function, restoring normal sleep breathing and avoidance of high altitude. Examples of lung disease are
- Interstitial lung disease
- Mixed restrictive and obstructive pulmonary diseases
- Breathing problems when sleeping
- Alveolar hypoventilation disorder
- Prolonged exposure to high altitudes
- Developmental dysfunction.
Group IV- Pulmonary Hypertension Associated With Blood Clots in The Lung
It is caused by blood clot in the lungs and rarely referred to as chronic thromboembolic pulmonary hypertension. Some of the examples for blood clot in the lungs/pulmonary obstruction are
- Tumors within the blood vessels like Angiosarcoma
- Inflammation of the arteries
- Pulmonary artery stenosis of the congenital form
Group V- PH Associated With Blood and Other Rare Disorders
They are the categories doesn’t fit in the first IV group. Some of the examples for group V disease are
- Chronic hemolytic anemia and other blood disorders
- Medical conditions like sarcoidosis, neurofibromatosis, and vasculitis
- Physiological conditions like Glycogen storage disease and thyroid disorders
- Others disease like fibrosing mediastinitis, chronic kidney dysfunction, and segmental pulmonary hypertension.
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