Prognostic Value and Risk Continuum of Noninvasive Fractional Flow Reserve Derived from Coronary CT Angiography

Abstract

Background Coronary CT angiography with noninvasive fractional flow reserve (FFR) predicts lesion-specific ischemia when compared with invasive FFR. The longer term prognostic value of CT-derived FFR (FFR_CT) is unknown. Purpose To determine the prognostic value of FFR_CT when compared with coronary CT angiography and describe the relationship of the numeric value of FFR_CT with outcomes. Materials and Methods This prospective subanalysis of the NXT study (Clinicaltrials.gov: NCT01757678) evaluated participants suspected of having stable coronary artery disease who were referred for invasive angiography and who underwent FFR, coronary CT angiography, and FFR_CT. The incidence of the composite primary end point of death, myocardial infarction, and any revascularization and the composite secondary end point of major adverse cardiac events (MACE: cardiac death, myocardial infarction, unplanned revascularization) were compared for an FFR_CT of 0.8 or less versus stenosis of 50% or greater on coronary CT angiograms, with treating physicians blinded to the FFR_CT result. Results Long-term outcomes were obtained in 206 individuals (age, 64 years ± 9.5), including 64% men. At median follow-up of 4.7 years, there were no cardiac deaths or myocardial infarctions in participants with normal FFR_CT. The incidence of the primary end point was more frequent in participants with positive FFR_CT compared with clinically significant stenosis at coronary CT angiography (73.4% [80 of 109] vs 48.7% [91 of 187], respectively; <i>P</i> < .001), with the majority of outcomes being planned revascularization. Corresponding hazard ratios (HRs) were 9.2 (95% confidence interval [CI]: 5.1, 17; <i>P</i> < .001) for FFR_CT and 5.9 (95% CI: 1.5, 24; <i>P</i> = .01) for coronary CT angiography. FFR_CT was a superior predictor compared with coronary CT angiography for primary end point (C-index FFR_CT, 0.76 vs coronary CT angiography, 0.54; <i>P</i> < .001) and MACE (FFR_CT, 0.71 vs coronary CT angiography, 0.52; <i>P</i> = .001). Frequency of MACE was higher in participants with positive FFR_CT compared with coronary CT angiography (15.6% [17 of 109] vs 10.2% [19 of 187], respectively; <i>P</i> = .02), driven by unplanned revascularization. MACE HR was 5.5 (95% CI: 1.6, 19; <i>P</i> = .006) for FFR_CT and 2.0 <b>(</b>95% CI: 0.3, 14; <i>P</i> = .46) for coronary CT angiography. Each 0.05-unit FFR_CT reduction was independently associated with greater incidence of primary end point (HR, 1.7; 95% CI: 1.4, 1.9; <i>P</i> < .001) and MACE (HR, 1.4; 95% CI: 1.1, 1.8; <i>P</i> < .001). Conclusion In stable patients referred for invasive angiography, a CT-derived fractional flow reserve (FFR_CT) value of 0.8 or less was a predictor of long-term outcomes driven by planned and unplanned revascularization and was superior to clinically significant stenosis on coronary CT angiograms. Additionally, the numeric value of FFR_CT was an independent predictor of outcomes. © RSNA, 2019 <i>Online supplemental material is available for this article.</i> See also the editorial by Dennie and Rubens in this issue.