Noninvasive Diagnosis of Ischemia-Causing Coronary Stenosis Using CT Angiography Diagnostic Value of Transluminal Attenuation Gradient and Fractional Flow Reserve Computed From Coronary CT Angiography Compared to Invasively Measured Fractional Flow Reserve

OBJECTIVES The aim of this study was to compare the diagnostic performance of coronary computed tomography angiography (CCTA)-derived computed fractional flow reserve (FFRCT) and transluminal attenuation gradient (TAG) for the diagnosis of lesion-specific ischemia. BACKGROUND Although CCTA is commonly used to detect coronary artery disease (CAD), it cannot reliably assess the functional significance of CAD. Novel technologies based on CCTA were developed to integrate anatomical and functional assessment of CAD; however, the diagnostic performance of these methods has never been compared. METHODS Fifty-three consecutive patients who underwent CCTA and coronary angiography with FFR measurement were included. Independent core laboratories determined CAD severity by CCTA, TAG, and FFRCT. The TAG was defined as the linear regression coefficient between intraluminal radiological attenuation and length from the ostium; FFRCT was computed from CCTA data using computational fluid dynamics technology. RESULTS Among 82 vessels, 32 lesions (39%) had ischemia by invasive FFR (FFR <= 0.80). Sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratio of TAG (<=-0.654 HU/mm) for detection of ischemia were 38%, 88%, 67%, 69%, 3.13, and 0.71, respectively; and those of FFRCT were 81%, 94%, 90%, 89%, 13.54, and 0.20, respectively. Receiver-operating characteristic curve analysis showed a significantly larger area under the curve (AUC) for FFRCT (0.94) compared to that for TAG (0.63, p < 0.001) and CCTA stenosis (0.73, p < 0.001). In vessels with noncalcified plaque or partially calcified plaque, FFRCT showed a larger AUC (0.94) compared to that of TAG (0.63, p < 0.001) or CCTA stenosis (0.70, p < 0.001). In vessels with calcified plaque, AUC of FFRCT (0.92) was not statistically larger than that of TAG (0.75, p = 0.168) or CCTA stenosis (0.80, p = 0.195). CONCLUSIONS Noninvasive FFR computed from CCTA provides better diagnostic performance for the diagnosis of lesion-specific ischemia compared to CCTA stenosis and TAG. (J Am Coll Cardiol Img 2012;5:1088-96) (C) 2012 by the American College of Cardiology Foundation