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

Abstract

Background: Fractional flow reserve calculated from coronary CT (FFR(CT)) is a novel method for determining lesion-specific ischemia.

Objective: To assess the effect of CT quality on accuracy of FFR(CT), we compared performance of FFR(CT) 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.

Methods: FFR(CT) was performed on 159 vessels in 103 patients undergoing CT, FFR(CT), and FFR. Ischemia was defined as FFR(CT) and FFR ≤ 0.80, and severe stenosis by CT was defined by ≥50% reduction in luminal diameter. FFR(CT) and CT stenosis were compared with FFR, which served as the reference.

Results: On a vessel basis, accuracy of FFR(CT) 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 FFR(CT) 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 FFR(CT) and CT stenosis on a patient basis. In 42 subjects who underwent coronary calcium scanning, accuracy of FFR(CT) was 77.8% (n = 18), 100% (n = 11), and 100% (n = 13) for coronary calcium scores of 0-100, 101-400, and >400, respectively.

Conclusions: Accuracy of FFR(CT) is superior to CT stenosis for determining lesion-specific ischemia. The performance of FFR(CT) remains robust across an array of factors known to adversely affect CT quality.