Lipid deposition in the media of human coronary arteries.

The coronary arteries of 52 unselected hearts obtained at autopsy and showing various types and degrees of intimal hyperplasia and atherosclerosis were investigated by staining for lipids and by histochemistry with regard to the lipid deposits in the media. These were found in focal areas in 47 cases and in 220 of 254 sections examined (86.2%). Lipids occur in the smooth muscle cells (intracellular type), or in the extracellular space of the media. Areas of intracellular involvement (44.6% of sections) contain relatively large amounts of lipids and usually extend throughout the whole thickness of the media 55.4% of sections with areas of the intracellular type), whereas the extracellular lipid (31.6% of sections) is usually located in the inner half of the media. Lipids, as demonstrated by histochemical staining are similar to those of the intimal lesions. The extracellular lipid contains largely cholesterol and a small amount of phospholipids; intracellular lipid is composed of cholesterol esters (as indicated by the spherical crystals in the droplets) and of a small amount of phospholipids, probably sphingomyelins. Medial lipids have apparently infiltrated from the intima. The presence of lipids in the media seems to reflect a stage in the transmural removal of lipids from the intima to the adventitia, and indicates an efflux of lipids from the vascular wall. Atherosclerotic plaques with large atheromas are very often associated with intracellular lipid deposition in the media (73% of sections). Atheromas of younger persons are more frequently involved than those of older people.