What are the pathological features of primary pulmonary hypertension ?
They are those of plexogenic pulmonary arteriopathy (which also occurs in post-tricuspid left-to-right
atrial shunts such as VSD or PDA, and collagen vascular diseases), characterized by medial hypertrophy
and concentric intimal fibrosis of the pulmonary arteries with complex plexiform lesions.
Others have no
plexiform lesions or concentric intimal fibrosis, but rather have recanalized thrombotic small pulmonary
arteries which are said to be the result of small thrombi or recurrent emboli.
The least common
histological pattern is veno-occlusive disease.