Examples of Arterial Lesions Found in PAH

Figure 1. Medial Thickening and Eccentric Intimal Proliferation

Hypertrophy and hyperplasia contribute to the medial thickening. The intimal thickening may develop from cells of endothelial or medial origin. They show smooth muscle (myointimal) differentiation. Elastic van Gieson stain

Click here to see normal pulmonary arteries.

intima

Figure 2. Concentric, Non-laminar Intimal Thickening

Here, concentric, non-laminar intimal thickening narrows the lumen of this artery that also shows medial and adventitial thickening. Note the enlargement of the bronchial vessels around the bronchiole.

Outline the intimal fibromuscular thickening.

Figure 3. Concentric, Laminar Intimal Thickening

In contrast with figure 2, concentric, laminar intimal thickening has onion-skin-like layers in the intima. This thickening may show varying degrees of cellularity or fibrosis.

Figure 4. Fibrinoid Necrosis

This vessel from a patient with extralobar sequestration shows an example of mural necrosis that may occur with severe pulmonary hypertension. See Unknown 17

plexiform

Figure 5. Occlusive Intimal Proliferation, Plexiform, and Dilation Lesions

The central artery is occluded by non-laminar intimal proliferation. A bronchiole is present at the right.

Below the artery is a rounded collection of endothelial cells forming small channels--a plexiform lesion. It occurs at a branch point from the central parent artery. A necrotizing arteritis destroyed its wall prior to the proliferation of the small vessels.

Farther away are several blood-filled dilation lesions that probably represent collateral blood flow from bronchial vessels.

Find the plexiform lesion.

Comment: Lesions in figures 1 and 2 occur in all types of hypertensive lung disease. They are considered to be potentially reversible [1]. Lesions in figures 3, 4, and 5 are high-grade, irreversible lesions found in PAH and other situations with elevated pulmonary artery pressures; such as, thromboembolic pulmonary hypertension [2] and pulmonary sequestration.

Experimental Production of Plexogenic Angiopathy: In experiments designed to show the development of pulmonary hypertensive vascular changes in dogs, anastomosis of the aorta to a segmental branch of the pulmonary artery and ligation of the other branches produced systemic pressure in the lung [3]. After 4 months, lesions resembling plexiform and dilation lesions developed. The dilation (angiomatoid) lesions were shown, via injection of gelatin into the aorta, to be derived from enlarged bronchial collaterals. It was also shown that necrosis of the arterial walls preceded the development of the proliferative, obstructive plexiform lesions. Microthrombi were only occasionally observed.

References: To return to reference section after viewing abstract, click here before clicking on "abstract".

1. Wagenvoort C. Morphological substrate for the reversibility and irreversibility of pulmonary hypertension. Eur Heart J 1988; 9:7-12. Abstract

2. Moser K, Bloor C. Pulmonary vascular lesions occurring in patients with chronic major vessel thromboembolic pulmonary hypertension. Chest 1993; 103:685-692. Abstract

3. Saldana M, Harley R, Liebow A, Carrington C. Experimental extreme pulmonary hypertension and vascular disease in relation to polycythemia. Am J Pathol 1968; 52:935-981.

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Plexiform lesion

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