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 |