Relationship between tissue characterisations with 40 MHz intravascular ultrasound imaging and slow flow during coronary intervention

Abstract

To evaluate the plaque characteristics that predispose to the slow flow phenomenon during percutaneous coronary intervention (PCI). The slow flow phenomenon is a serious complication of PCI and is associated with poor prognosis. It is difficult to predict this phenomenon from greyscale intravascular ultrasound (IVUS) data obtained before PCI. iMap™ is a new software package for assessing plaque composition from data obtained by 40 MHz IVUS imaging. Ninety-five consecutive patients underwent 40 MHz IVUS, including 33 with acute coronary syndrome. Plaque volume was calculated by IVUS and plaque components were detected by iMap software. Plaques were characterised as fibrotic, lipidic, necrotic, or calcified. Correlations among plaque characteristics and the slow flow phenomenon were analysed. Slow flow during PCI was observed in 11 patients (11.6%). Both the absolute volume and percentage of necrotic plaque were significantly higher in the slow flow group than the normal flow group (43.3±33.5 mm3 vs. 20.1±17.2 mm3, p=0.0004, 19.7±5.1% vs. 14.6±8.3%, p=0.047). Receiver-operating characteristic analysis showed that the necrotic plaque volume and necrotic plaque ratio were significantly better predictors of slow flow during PCI compared with total plaque volume. The cut-off value of necrotic plaque volume for predicting slow flow was 21.6 mm3 (sensitivity of 81.8% and specificity of 61.9%). Characterisation of plaque by IVUS with iMap analysis may predict slow flow during PCI.