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:
(2) planar (square wave in cross section)
• 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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