Assessment of lesion complexity and morphology using coronary lesion classification systems

Overview
According to the Abrupt Vessel Closure - AHA Task Force Definition, as modified by Ellis et al., coronary lesion complexity is graded as A, B1, B2, and C.

Type A
<10mm, discrete, concentric readily accessible, <45 degree angle smooth contour, little or no calcification, less than totally occluded, not ostial, no major side branch involvement, absence of thrombus.

Type B
One of the following characteristics: 10-20mm, eccentric, moderate tortuosity or proximal segment, irregular contour, presence of any thrombus grade, moderate or heavy calcification, total occlusion <3 months old, ostial lesion or bifurcation lesion requiring two guide wires.

Type B2
Two or more of the following characteristics: 10-20mm, eccentric, moderate tortuosity or proximal segment, irregular contour, presence of any thrombus grade, moderate or heavy calcification, total occlusion <3 months old, ostial lesion or bifurcation lesion requiring two guide wires.

Type C
>20 mm diffuse, excessive tortuosity of proximal segment, total occlusion >3 months old and/or bridging collaterals inability to protect major side branches, degenerated vein graft with friable lesions.