Pulmonary Hypertension WHO Classification

Pulmonary hypertension (PH) is a severe, rare lung disease characterized by high blood pressure in the pulmonary arteries. Due to the condition, the pulmonary arteries, which are responsible for transporting the blood from the right heart ventricle to the lungs, become narrowed and thickened. In order to properly pump the blood, the heart needs to work harder, which can lead to enlargement and weakening of the organ, as well as potential right heart failure.

There is currently no cure for pulmonary hypertension, but there are treatments that can help patients cope with the symptoms, which include shortness of breath, tiredness, chest pain or pressure, irregular heartbeat, pain on the upper right side of the abdomen and decreased appetite. Symptoms, diagnosis and treatment of pulmonary hypertension are different according to the different subtypes of the disease. In order to produce, maintain and implement international health information standards, the World Health Organization (WHO) defined a PH classification.

How Is The Pulmonary Hypertension WHO Classification Determined

The International Classification of Diseases (ICD) is created by the organization and comprises a standard diagnosis tool for physicians, nurses, other providers, researchers, health information managers and coders, health information technology workers, policy-makers, insurers and patient organizations. To determine the classification of pulmonary hypertension, the WHO analyzed the general health situation of patients, as well as the disease’s incidence and prevalence.

The pulmonary hypertension WHO classification is used for numerous purposes, including records, death certificates, information storage, diagnosis retrieval, national mortality and morbidity statistics, reimbursement, resource allocation, and other clinical, epidemiological and quality purposes, and the organization expects it to help fight the disease.

Different Pulmonary Hypertension WHO Classification Groups

The pulmonary hypertension WHO classification was updated in 2009, placing a greater importance on treating the underlying cause of the disease. There are now five groups, while the previous classification was more focused on whether the underlying cause was known and included only two categories: primary or idiopathic pulmonary hypertension, and secondary pulmonary hypertension. In all of the different groups, the average pressure in the pulmonary arteries is 25 mmHg or more at rest or 30 mmHg during physical activity, the normal levels between 8 and 20 mmHg at rest.

  • Group 1 includes the subtypes of pulmonary hypertension associated with abnormalities in the arterioles, the small branches of the pulmonary arteries, such as pulmonary arterial hypertension (PAH), and idiopathic pulmonary hypertension (IPH), which is the type of PH diagnosed when the causes of the disease are not known. Also in this group is inherited pulmonary hypertension, as well as pulmonary hypertension caused by connective tissue diseases that affect the body’s structure or composition of the tissue like scleroderma, congenital heart problems, high blood pressure in liver (portal hypertension), HIV, thyroid gland disorder, sickle cell disease, glycogen storage disorders, and rare blood conditions like pulmonary veno-occlusive disease or pulmonary capillary hemangiomatosis.
  • Group 2 refers to pulmonary hypertension caused by left heart disease, including cardiomyopathy, diastolic dysfunction, mitral stenosis, mitral regurgitation, aortic stenosis, and aortic regurgitation. The left side of the heart pumps blood to the entire body but the lungs, but about 60% of patients with severe left ventricle dysfunction also develop pulmonary hypertension, since the blood flows through the entire heart, affecting the right side as well.
  • Group 3 includes pulmonary hypertension resulting from lung diseases or shortage of oxygen in the body (hypoxia), with chronic obstructive pulmonary disease (COPD); interstitial lung disease; and sleep-disordered breathing, a group of diseases that affect the breathing during the sleep like obstructive sleep apnoea (OSA) being the most common diseases that can result in pulmonary hypertension.
  • Group 4 refers to pulmonary hypertension secondary to blood clots, which are the body’s response to bleeding and injuries but can harm the heart and lungs when they occur without an apparent cause. Pulmonary embolus are blood clots that travel to the lungs and pulmonary thrombosis are clots that are formed in the lungs, which can block the pulmonary arteries.
  • Group 5 is the last category and it includes other less common causes that do not fit into any of the other four groups. Sarcoidosis, which is a condition that results in inflammation of different organs like the lungs and lymph nodes, histiocytosis X, a rare disorder that causes scarring, granulomas and air-filled cysts mostly in the lungs, as well as compression of the blood vessels in the lungs, which can occur for numerous reasons like tumors, are some of the causes for pulmonary hypertension in the fifth group.