Table 6 Cap index definition using plaque cap thickness related to plaque vulnerability and AHA plaque classifications
Cap index | Description | AHA type | Description | Vulnerability level |
|---|---|---|---|---|
0 | No component | Type I or Type II | Normal or slight intimal thickening | Very stable |
1 | Minimum cap thickness > 200 µm | Type III | Moderate intimal thickening, no extracellular lipid, calcification or significant inflammation | Stable |
2 | 150 µm < minimum cap thickness ≤ 200 µm | Type IV, Vb and Vc | Small lipid core (< 30% of plaque size); calcification may be present; thick fibrous cap(> 150 μm); | Slightly unstable |
3 | 65-m < min cap thickness ≤ 150 µm | Type Va | Moderate lipid core(30–40% of plaque size) and fibrous cap(65–200 μm); moderate intraplaque hemorrhage and inflammation | Moderately unstable |
4 | Min cap thickness ≤ 65 µm | Type VI | Large lipid core(> 40%); thin fibrous cap(< 65 μm); large intraplaque hemorrhage; extensive inflammation; previous plaque rupture | Highly unstable |