Feasibility and Diagnostic Performance of Functional SYNTAX Score Derived from Dynamic CT Myocardial Perfusion Imaging.

BACKGROUND: Computed tomography (CT) fractional flow reserve (FFR)–derived functional SYNTAX score (FSS CT-FFR ) is a valuable method for guiding treatment strategy in patients with multivessel coronary artery disease. Dynamic CT myocardial perfusion imaging (CT-MPI) demonstrates higher diagnostic accuracy than CT-FFR in identifying hemodynamically significant coronary artery disease. We aimed to evaluate the feasibility of CT-MPI–derived FSS (FSS CT-MPI ) with reference to invasive FSS. METHODS: In this retrospective study, patients with multivessel coronary artery disease who underwent dynamic CT-MPI+ coronary CT angiography and invasive coronary angiography or FFR within 4 weeks were consecutively included. Invasive (FSS invasive ) and noninvasive FSS (FSS CT-MPI and FSS CT-FFR ) were calculated by an online calculator, which assigned points to lesions with hemodynamic significance (defined as FFR invasive ≤0.80, invasive coronary angiography diameter stenosis ≥90%, CT-FFR ≤0.80, and myocardial ischemia on CT-MPI). Weighted κ value and net reclassification index were calculated to determine the consistency and incremental discriminatory power of FSS CT-MPI . Receiver operating characteristic curve analysis was used for the comparison of FSS CT-MPI and FSS CT-FFR in detecting intermediate- to high-risk patients. RESULTS: A total of 119 patients (96 men; 64.6±10.6 years) with 305 obstructive lesions were included. The average FSS CT-MPI , FSS CT-FFR , and FSS invasive were 15.58±13.03, 16.18±13.30, and 13.11±12.22, respectively. The agreement on risk classification based on the FSS CT-MPI tertiles was good (weighted κ, 0.808). With reference to FSS invasive , FSS CT-MPI correctly reclassified 27 (22.7%) patients from the intermediate- to high SYNTAX score group to the low-score group (net reclassification index, 0.30; P <0.001). In patients with severe calcification, FSS CT-MPI had better diagnostic value than FSS CT-FFR in detecting intermediate- to high-risk patients when compared with FSS invasive (area under the curve, 0.976 versus 0.884; P <0.001). CONCLUSIONS: Noninvasive FSS derived from CT-MPI is feasible and has strong concordance with FSS invasive . It allows accurate categorization of FSS in patients with multivessel coronary artery disease, in particular with severe calcification.