Background Prospective VH-IVUS studies indicate that <10% higher-risk plaques cause clinical events over 3 years, indicating that other factors also determine plaque rupture. Plaque rupture is believed to occur when plaque structural stress (PSS) exceeds its mechanical strength.

Methods We analysed plaque structure and composition in 4,053 VH-IVUS frames from 32 fibroatheromas with rupture from the VIVA study and 32 fibroatheromas without rupture on optical coherence tomography from a stable angina cohort. PSS was calculated by finite element analysis.

Results PSS increased with increasing lumen area (r=0.46; p=0.001), lumen eccentricity (r=0.32; p=0.001), and necrotic core ≥10% (r=0.12; p=0.001), but reduced when dense calcium ≥10% (r=-0.12; p=0.001). Ruptured fibroatheromas showed higher PSS (133 vs 104 kPa; p=0.002) and variation in PSS (55 vs 43 kPa; p=0.002) than non-ruptured fibroatheromas. PSS >135 kPa was a good predictor of rupture in higher-risk regions.

Conclusions PSS is determined by plaque composition, plaque architecture, and lumen geometry. PSS and PSS variability are increased in plaques with rupture. Incorporating PSS into plaque assessment may improve identification of rupture-prone plaques.

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Abstract 2 Figure 1