Table 1. Pathological changes and disease mechanisms in pulmonary hypertension (PH) subtypes
PH subtypePathological changesContributory mechanisms
PAHPathological lesions in distal pulmonary arteries
Medial hypertrophy
Intimal proliferative and fibrotic changes
Adventitial thickening with perivascular inflammatory infiltrates and thrombotic lesions
Endothelial dysfunction, leading to changes in vasoactive and growth regulatory factors
Vascular cell proliferation
PH-LHDEnlarged and thickened pulmonary veins
Pulmonary capillary dilatation
Interstitial oedema
Alveolar haemorrhage
Lymphatic vessel and lymph node enlargement
Medial hypertrophy and intimal fibrosis of distal pulmonary arteries
Vasoconstrictive reflexes arising from stretch receptors localised in the left atrium and pulmonary veins
Endothelial dysfunction
Proliferative remodelling of the pulmonary vessel wall
PH-ILDMedial hypertrophy
Intimal obstructive proliferation of the distal pulmonary arteries
Destruction of vascular bed in areas subject to emphysema or fibrosis
Hypoxic vasoconstriction
Endothelial dysfunction leading to imbalance in vasoactive signalling molecules
Mechanical stress of hyperinflated lungs
Capillary loss
Toxic effects of cigarette smoke
CTEPHPersistent organised thrombi in the medial layer of the pulmonary vasculature
Vessel occlusion
Remodelling of the major pulmonary vasculature
Small-vessel pulmonary arteriopathy (indistinguishable from changes seen in PAH)
Non-resolution of emboli
Endothelial dysfunction from shear stress, pressure and inflammation
Cytokine release
In situ thrombosis
Vasculotrophic mediator release
  • PAH: pulmonary arterial hypertension; LHD: left heart disease; ILD: interstitial lung disease; CTEPH: chronic thromboembolic PH. Modified from [1].