Effect of image quality on diagnostic accuracy of noninvasive fractional flow reserve: Results from the prospective multicenter international DISCOVER-FLOW study

BackgroundFractional flow reserve calculated from coronary CT (FFRCT) is a novel method for determining lesion-specific ischemia.ObjectiveTo assess the effect of CT quality on accuracy of FFRCT, we compared performance of FFRCT with severe stenosis by CT in relation to image quality; heart rate; signal-to-noise ratio (SNR); and common CT artifacts, including calcification, motion, and poor contrast enhancement.MethodsFFRCT was performed on 159 vessels in 103 patients undergoing CT, FFRCT, and FFR. Ischemia was defined as FFRCT and FFR ≤ 0.80, and severe stenosis by CT was defined by ≥50% reduction in luminal diameter. FFRCT and CT stenosis were compared with FFR, which served as the reference.ResultsOn a vessel basis, accuracy of FFRCT was higher than CT stenosis for satisfactory or poor quality CTs (87.5% vs 64.6%), for heart rates > 65 beats/min (100% vs 52.9%), and for SNR less than the median (26.3) (84.4% vs 64.1%). Accuracy of FFRCT was superior to CT stenosis in the presence of calcification (85.7% vs 66.7%), motion (90.5% vs 57.1%), and poor contrast opacification (100.0% vs 71.4%). Similar relations were observed for exploratory analyses of FFRCT and CT stenosis on a patient basis. In 42 subjects who underwent coronary calcium scanning, accuracy of FFRCT was 77.8% (n = 18), 100% (n = 11), and 100% (n = 13) for coronary calcium scores of 0–100, 101–400, and >400, respectively.ConclusionsAccuracy of FFRCT is superior to CT stenosis for determining lesion-specific ischemia. The performance of FFRCT remains robust across an array of factors known to adversely affect CT quality.