Intravascular Ultrasound Profile Analysis of Ruptured Coronary Plaques

Angiographic studies have shown that lesions preceding nonfatal acute events are usually not hemodynamically significant. This has led to the concept that plaque ruptures occur at minimal disease sites. We used intravascular ultrasound to create a prerupture "profile" of unstable (vulnerable) plaques. We analyzed 112 ruptured plaques detected by intravascular ultrasound. Reference and lesion external elastic membrane (EEM) and lumen areas were measured to calculate prerupture estimates of plaque area, plaque burden (plaque/EEM area), eccentricity, area stenosis, and remodeling. The narrowest coefficients of variance were for lesion EEM area, maximum plaque thickness, and plaque burden, reference lumen area, and remodeling index (coefficients of variance 0.29, 0.25, 0.12, 0.29, and 0.18, respectively); conversely, there was great variability in measurements of calcification and lumen compromise (minimum lumen area and area stenosis). When using the 5 variables with the narrowest coefficient of variance, we found that 67% of ruptured plaques fit all of following 10th or 90th percentile parameters (>14.3 mm² lesion EEM area, >8.1 mm² reference lumen area, >1.6 mm maximum lesion plaque thickness, >0.63 lesion plaque burden, and >0.87 remodeling index). Further, 89% of ruptured plaques fit 4 of 5 parameters and 96% fit 3 of 5 parameters. In conclusion, plaque ruptures do not occur at minimal disease sites. Rather, vulnerable (rupture-prone) plaques predictably have significant plaque accumulation and remodeling and occur in larger arteries. It is only the degree of lumen compromise that is variable and often insignificant.