Table 1.

American Heart Association Classification of Atherosclerotic Lesions ⁷-⁹,¹⁵

	Lesion Type		Cellular Composition
I	Initial Change		Isolated macrophage foam cells
II	Minimal Change	IIa: Progression-prone	Multiple layers of foam cells Few lymphocytes Isolated mast cells	Abundant SMCs
		IIb: Progression-resistant		Few SMCs
III	Preatheroma		Isolated pools of densely packed extracellular lipids SMCs accumulate lipid droplets
IV	Atheroma		Confluent core of extracellular lipids Increased number of lymphocytes SMCs decrease in number, remaining SMCs have thick basement membranes
V	Fibroatheroma		Fibrous tissue and collagen added Intimal SMCs increase in number
VI	Hemorrhagic/Thrombotic Lesion		Lesion becomes fissured and/or thrombotic
VII	Calcific Lesion		Calicification predominates
VIII	Fibrotic Lesion		Fibrous tissue changes predominate Lipid core is nearly absent