Computational structural analysis based on intravascular ultrasound imaging before in vitro angioplasty: Prediction of plaque fracture locations

OBJECTIVES: This in vitro study was designed to test the hypothesis that a structural analysis based on intravascular ultrasound images of atherosclerotic vessels obtained before angioplasty can be used to predict plaque fracture locations and balloon pressures required to cause fracture. BACKGROUND: Intravascular ultrasound imaging performed before interventional procedures has potential for providing information useful for guiding therapeutic strategies. METHODS: Intravascular imaging was performed on 16 atherosclerotic human iliac vessel segments obtained freshly at autopsy; balloon angioplasty was then performed with 1-min inflations at 2 atm, increasing in 2-atm increments until fracture of the lumen surface occurred. Fracture locations were confirmed by histopathologic examination. Structural analysis of these images was performed with a large strain finite element analysis of the image that calculated the distribution of stress in the vessel with 2 atm of lumen pressure. RESULTS: Structural analysis demonstrated a total of 30 high circumferential stress regions in the vessels (mean 1.9 high stress regions/vessel). A total of 18 plaque fractures occurred in the 16 vessel segments. Of the 17 fractures that occurred in the 15 specimens with regions of high circumferential stress, 14 (82%) occurred at a high stress region (p < 0.0001). However, there was no significant relation between the peak stresses estimated by structural analysis and the ultimate balloon inflation pressure required to cause fracture. CONCLUSIONS: Structural analysis based on intravascular ultrasound imaging performed before in vitro balloon angioplasty can predict the locations of plaque fracture that usually accompany angioplasty. However, these data suggest that intravascular ultrasound may not be useful for predicting the ultimate balloon inflation pressure necessary to cause fracture, possibly because of the variable fracture properties and microscopic structure of atherosclerotic tissues.