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) 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) 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) and noninvasive FSS (FSS and FSS) were calculated by an online calculator, which assigned points to lesions with hemodynamic significance (defined as FFR ≤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. Receiver operating characteristic curve analysis was used for the comparison of FSS and FSS 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, FSS, and FSS were 15.58±13.03, 16.18±13.30, and 13.11±12.22, respectively. The agreement on risk classification based on the FSS tertiles was good (weighted κ, 0.808). With reference to FSS, FSS correctly reclassified 27 (22.7%) patients from the intermediate- to high SYNTAX score group to the low-score group (net reclassification index, 0.30; <0.001). In patients with severe calcification, FSS had better diagnostic value than FSS in detecting intermediate- to high-risk patients when compared with FSS (area under the curve, 0.976 versus 0.884; <0.001).

Conclusions: Noninvasive FSS derived from CT-MPI is feasible and has strong concordance with FSS. It allows accurate categorization of FSS in patients with multivessel coronary artery disease, in particular with severe calcification.