Functional and Anatomical Testing in Intermediate Risk Chest Pain Patients with a High Coronary Calcium Score: Rationale and Design of the FACC Study. 
Current guidelines do not recommend coronary computed tomography angiography (CCTA) in patients with high levels of coronary calcium, as severe calcification leads to difficulties in estimating stenosis severity due to blooming artifacts obscuring the vessel lumen.  Whether the CCTA-derived fractional flow reserve (FFRCT) improves the diagnostic performance of CCTA in patients with high levels of coronary calcification has not been sufficiently evaluated.  We hypothesize that a noninvasive diagnostic strategy using FFRCT will perform comparably to an invasive diagnostic strategy in the detection of hemodynamically significant coronary artery disease (CAD) in clinical stable chest pain patients with high levels of coronary calcium.  In this prospective, blinded, multicenter study, patients with suspected stable CAD referred for CCTA and demonstrating an Agatston score >399 will be included.  Patients accepting inclusion will, in addition to CCTA, undergo invasive coronary angiography (ICA) and invasive FFR measurement.  FFRCT analyses are performed by an external core laboratory blinded to any patient data, and the FFRCT results are blinded to all participating study sites.  The primary objective is to evaluate whether FFRCT can identify patients with and without hemodynamically significant CAD, when ICA with FFR is the reference standard.  A negative study result would question the clinical usefulness of FFRCT in patients with high levels of coronary calcium.  A positive study result, however, would imply a reduction in the number of patients referred for coronary catheterization and, at the same time, increase the proportion of patients with hemodynamically significant CAD at the subsequent invasive examination.