| I | No involvement at any timepoint (Z score always < 2) | No dilated lesions |
| II | Dilation only (Z score 2 to < 2.5) | Transient dilation in the acute phase (normalized by 30 days after onset) |
| III | Small aneurysm (Z score ≥ 2.5 to < 5)3.1 Current or persistent3.2 Decreased to dilation only or normal luminal dimension | Residual aneurysm formation equivalent to or greater than dilatation > 30 days, normalized by 1 year after onset |
| IV | Medium aneurysm (Z score ≥ 5 to < 10, and absolute dimension < 8 mm)4.1 Current or persistent4.2 Decreased to small aneurysm4.3 Decreased to dilation only or normal luminal dimension | Residual unilateral or bilateral coronary artery aneurysm at coronary angiography more than 1 year later |
| V | Large and giant aneurysm (Z score ≥ 10, or absolute dimension ≥ 8 mm)5.1 Current or persistent5.2 Decreased to medium aneurysm5.3 Decreased to small aneurysm5.4 Decreased to dilation only or normal luminal dimension | Coronary artery stenosis at coronary angiography (a) No ischemic findings (b) Ischemic finding |