Table 1:

Original American Heart Association (AHA) classification for atherosclerotic plaques, and modified classification adapted for CT

Type of Plaque	AHA Histologic Classification of Atherosclerotic Plaques	Classification of Atherosclerotic Plaques Adapted for CT
0	No intimal thickening	No intimal thickening
1	Initial lesion; not grossly apparent plaque; foam cells	Thin plaque with no calcification
2	Fatty streak; lesion grossly apparent; foam cells and smooth muscle cells contain lipid droplets
3	Preatheroma; foam cells contain lipid droplets and increased number of smooth muscle cells; raised fatty streak	Plaque with small lipid cores and no calcification
4	Atheroma; massive extracellular lipid pool (lipid core); grossly visible; infiltrated with foam cells and smooth muscle cells	Plaque with a large lipid core, covered by a fibrous cap, possible small calcifications
5a	Fibroatheroma; type IV with a fibrous cap
5b	Calcified plaque; lesion with a lipid core or fibrotic tissue, with large calcifications	Plaque with a lipid core or fibrotic tissue, with large calcifications
5c	Fibrotic plaque: fibrous connective tissue, no lipid core	Plaque with fibrous tissue, no lipid core, possible small calcifications
6a	Ulcerations	Ulcerations
6b	Wide hemorrhage	Wide hemorrhage
6c	Thrombosis	Thrombosis