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

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.