Criteria for American Heart Association lesion classification system and correspondence with classification of gross arterial specimens

AHA grade	Criteria	Comments and corresponding gross classification
0	Normal artery with or without adaptive intimal thickening; no hold	Normal tissue
1	Isolated MFCs containing lipid; no extracellular lipid; variable adaptive intimal thickening grossly with lipid staining	Initial atherosclerotic lesion, sometimes visible grossly with lipid staining
2	Numerous MFCs, often in layers, with fine particles of extracellular lipid; no distinct pools of extracellular lipid: variable adaptive intimal thickening	Fatty streak, visible grossly with III staining
3	Numerous MFCs with ≥ pools of extracellular lipid; no well-defined core of extracellular lipid	Fatty plaque, raised fatty streak, intermediate lesion, or transitional lesion
4	Numerous MFGs plus well-defined core of extracellular lipid, but with luminal surface covered by relatively normal intima	Atheroma, fibrous plaque, or raised lesion
5	Numerous MFCs, well-defined core or multiple cores of extracellular lipid, plus reactive fibrotic cap, vascularization, or calcium	Fibroartherema, fibrous plaque, or raised lesion
6	All of the above plus surface defect, hematoma, hemorrhage, or thrombosis	Complicated lesion

MFC: macrophage foam cell; AHA: American Heart Association.

Graphic 56922 Version 2.0