Pulmonary Arterial Hypertension: what is it?

Pulmonary arterial hypertension (PAH) is a serious disease of the arteries connecting the lungs to the heart (the pulmonary arteries). Under normal conditions, the right side of the heart (the right atrium and right ventricle) pumps venous blood through the lungs, so the blood can pick up oxygen.

When Pulmonary Arterial Hypertension (PAH) develops, blood flow through the pulmonary arteries is restricted and the right side of the heart is put under increasing strain to pump blood through to the lungs.
Pulmonary Arterial Hypertension (PAH) can be caused by a number of changes in the pulmonary arteries:

• an increase in the number and size of the cells making up the vessel, causing it to become thicker and narrower

• scarring of the vessels which make them stiffer or thicker (Fibrosis)

• Inflammation

• tightening or narrowing of the vessels (this is called 'Vasoconstriction').

  Figure 1: Click to enlarge

These changes in the blood vessels raise the pressure and increase the resistance to blood flow through the lungs, making it harder for the heart to pump blood through the lungs. Over time, due to the additional strain, the heart begins to work less effectively and eventually, the right heart can fail (this is known as 'right ventricular failure').

Common symptoms of Pulmonary Arterial Hypertension (PAH) include breathlessness, fainting, fatigue, chest pain, chest tightness, palpitations, limited exercise capacity and swollen ankles and legs.¹

References
1. Gibbs J, Higgenbottam T. Recommendations on the management of pulmonary hypertension in clinical practice. Heart (2001);86(1):i1-i13