2.2.1. IVUS Analysis and Identification of CN/NC

All study patients had prestent IVUS imaging. IVUS-guided RA using either the OptiCross™ (Frequency 60 MHz, Boston Scientific, Marlborough, MA, USA) or Eagle Eye Platinum™ (Frequency 20 MHz, Philips, Rancho Cordova, CA, USA) system was used depending on the decision of the operator. OptiCross™ was used in 45% of patients in this study. Thirty-six (20%) patients IVUS was obtained prior RA. One hundred and sixty-four patients (80%) the IVUS catheter could not pass the lesion before RA. IVUS imaging obtained after RA.

An experienced intravascular imaging technician and experienced interventionists who were blinded to the clinical outcome reviewed the angiographic and IVUS imaging data. Intraobserver and interobserver variability yielded good concordance for the diagnosis of CN (k = 0.95 and k = 0.90, respectively).