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

Abstract

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.

Keywords: computed tomography angiography; coronary artery disease; fractional flow reserve, myocardial; hemodynamics; myocardial perfusion imaging.