Pulmonary Arterial Hypertension
Pulmonary Hypertension (PH) is a rare condition and a general term meaning there is high blood pressure in the lungs.
WHO groups of PH:
Using the WHO groups there are 5 different types of PH according to their cause:
Group 1: Pulmonary Arterial Hypertension (PAH) (Relevant to this question)
Group 2: PH due to left heart disease
Group 3: PH due to lung disease
Group 4: PH due to chronic blood clots in the lungs
Group 5: PH due to unknown causes
PAH:
The pulmonary arteries bring blood into the lungs for gas exchange (O2 in and CO2 out) vie the right ventricle of the heart. In PAH the pulmonary arteries are narrowed, thickened, or stiff. The right side of the heart (the right ventricle) needs to work harder to push blood through the narrowed arteries. Over time this may cause damage to the right ventricle and heart failure.
Hypothetical image of cell wall proliferation causing narrowing of the pulmonary arteries Ref
Types of PAH:
- Idiopathic PAH - means cause unknown
- Heritable PAH - linked to genes inherited from family members.
- PAH induced by drug and toxins (eg amphetamines)
- PAH due to other medical conditions - congenital heart disease, liver disease, HIV, connective tissue diseases (such as scleroderma and lupus), and schistosomiasis
While there are treatment options for PAH there is currently no known cure, and it is a progressive disease (will get worse over time without treatment).
WHO functional classes for PH:
The WHO functional class (FC) describes how severe a patient’s pulmonary hypertension (PH) symptoms are (not specific for PAH). There are four different classes – I is the mildest and IV the most severe form of PH.
Class 1: Symptom free at rest and during physical activity
Class 2: No symptoms at rest but normal activities such as climbing stairs or making the bed may cause some discomfort and shortness of breath (SOB)
Class 3: Resting may be symptoms free but normal chores around the house are greatly limited by SOB or feeling tired.
Class 4: Symptoms at rest and severe symptoms with activity.
The WHO FC at diagnosis and at follow-up remains one of the strongest predictors of survival in PAH.