Type A Type B Type C
Lesion character
Length < 10 mm 10 to 20 mm > 20 mm
Angulation < 45 deg 45 to < 90 deg 90 deg or more
Contour Smooth Irregular
Calcium Nil or little Moderate or heavy
Thrombus Present Absent
Total occlusion < 3 months old > 3 months old
Eccentricity Concentric Eccentric
Lesion location
Ostial or not Non-ostial Ostial
Tortuosity or proximal segment Nil or mild Moderate Severe
Major side branch involvement Absent Bifurcation lesion needing guidewire Inability to protect major side branch
Other
Degenerated vein graft with friable lesion