The World Health Organization (WHO) developed a system of functional classes to describe the severity of pulmonary hypertension cases.
Knowing what type of pulmonary hypertension and functional class you have helps doctors decide which PH treatments will be most effective. One goal of treatment is to improve functional class. Progressing to a more severe functional class indicates that treatment is not working.
Functional classes of pulmonary hypertension
WHO organizes PH into four classes based on the severity of the symptoms, specifically the limitations PH imposes upon activities.
People with class I pulmonary hypertension do not experience any PH symptoms, either at rest or with exercise.
Pulmonary hypertension is considered class II when a person experiences no PH symptoms at rest but feels uncomfortable and short of breath while performing their usual daily activities.
Someone with class III pulmonary hypertension may or may not experience symptoms at rest. Normal household chores and other daily activities are limited by extreme fatigue and shortness of breath. Symptoms may necessitate frequent breaks to rest.
In class IV pulmonary hypertension, people experience symptoms at rest and during activity. Fainting is possible, especially when bending over. Edema (swelling) in the feet and ankles is common.