The plaque ulceration index (UI) can be used to quantitate the irregularity in an area of coronary atherosclerotic plaque.


Lesion selection: area of convexity or irregularity


ulceration index =

= (maximal intralesional distance in mm) / (minimal adjacent intralesional distance in mm)



• The points used to measure the maximal and minimal distances should be adjacent to each other within a region of convexity. The index is not calculated from the maximal and minimal width in a length of plaque material.


By definition an index of 1 is assigned if the lesion is:

(1) convex

(2) planar (square wave in cross section)

(3) smooth



• minimum ulceration index: 1

• maximum: > 8

• Davies et al (1991) found that 58% of patients with an index > 6 showed early clinical instability after thrombolysis. Only 8% of patients with an index <= 6 showed clinical instability after thrombolysis.


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