Prognosis of CT-derived Fractional Flow Reserve in the Prediction of Clinical Outcomes

Purpose To examine the prognostic implication of fractional flow reserve (FFR) derived from coronary CT (FFRCT) in routine clinical practice. Materials and Methods Patients referred for FFRCT analysis at a single center between October 2015 and June 2017 were retrospectively included and followed up for rates of invasive angiography and clinical events. Two hundred seven patients underwent successful FFRCT analysis with seven lost to follow-up, leaving 200 (mean age ± standard deviation, 62.4 years ± 10.0; 49 [24.5%] women) patients for analysis. At coronary CT angiography, patients were categorized as having significant stenosis (SS) in the presence of a diameter stenosis greater than or equal to 50% (hereafter, SS positive) and flow limitation in the presence of a postlesion (that is, FFRCT measured 2 cm to the distal aspect of the lesion) FFRCT less than 0.80 (hereafter, FFRCT positive). Vessel-oriented clinical events (VOCEs) were defined as vessel-related late revascularization (>90 days), myocardial infarction, and cardiac mortality. Results At CT angiography, 130 (65%) studies were SS positive and 63 (31.5%) were FFRCT positive. At median follow-up of 477 days (range, 252–859 days), there were 26 VOCE end points in 22 patients: 22 revascularizations and four nonfatal myocardial infarctions. VOCE end points occurred in zero of 58 (0%) of SS-negative and FFRCT negative patients, in eight of 79 (10.1%) of SS-positive and FFRCT-negative patients, in zero of 12 (0%) of SS-negative and FFRCT-positive patients, and in 18 of 51 (35.3%) of SS-positive and FFRCT-positive patients (log-rank χ2 = 30.1; P < .001). At multivariable Cox regression, both FFRCT (hazard ratio per 0.1 decrease, 1.54 [95% confidence interval: 1.1, 2.2] P = .013) and stenosis (hazard ratio per unit increase, 2.16 [95% confidence interval: 1.25, 3.72] P = .006) were independently associated with VOCE. Conclusion Stenosis and FFRCT are independent predictors of intermediate-term outcomes. In the absence of a stenosis greater than 50%, a positive FFRCT result is not associated with an increased intermediate risk. Keywords: Adults, CT-Angiography, Cardiac, Heart, Outcomes Analysis © RSNA, 2019 Supplemental material is available for this article. See also commentary by Fairbairn and Bull in this issue.