The predictive factors affecting false positive in on-site operated CT-fractional flow reserve based on fluid and structural interaction

Background

A novel algorithm has been developed for the on-site analysis of CT-fractional flow reserve (CT-FFR) using fluid structural interactions. There have been no reports on the factors affecting the diagnostic performance of CT-FFR using this algorithm. We evaluated the factors predictive of false-positive CT-FFR findings compared to invasive FFR as a reference standard.

Methods

The subjects were 66 consecutive cases (81 vessels) who underwent invasive FFR assessment within 90 days of the detection of 30–90% stenosis of one vessel of the major coronary artery, from among patients with suspected coronary arterial disease who underwent one-rotation scanning by 320-row coronary CT angiography (CCTA). The prospective CCTA mode was used for all patients, with the X-ray exposure set in a range of 70–99% of the RR interval. The FFR was calculated on-site from multiple cardiac phases. Factors associated with a false-positive finding of functional stenosis on CT-FFR, defined as an invasive FFR of ≤0.80, were evaluated using logistic regression analysis.

Results

Thirty-nine vessels (48.1%) had an invasive FFR of ≤0.80. CT-FFR and invasive FFR values disagreed in 13 vessels in 13 patients. The values were false positive in 12 of the vessels. In an analysis of patient characteristics, the body mass index (odds ratio, 1.33; 95%CI, 1.06–1.67; p = 0.01) and Image noise (odds ratio, 1.18; 95%CI, 1.01–1.40; p = 0.04) were predictive of false-positive findings. The presence of calcified plaque (odds ratio, 5.16; 95%CI, 1.06–20.85; p = 0.01) was the only significant predictive factor in a vessel-based analysis of lesion characteristics.

Conclusions

The presence of calcified plaque exerted a significant effect on the diagnostic performance of CT-FFR, and did so independently of the degree of calcification indicated by the Agatston score.

The diagnostic performance of on-site workstation-based computed tomography-derived fractional flow reserve. Comparison with myocardium perfusion imaging

To compare the diagnostic performance of on-site workstation-based computed tomography-derived fractional flow reserve (CT-FFR)Few data of CT-FFR were reported regarding the diagnostic performance for detecting hemodynamically significant coronary artery disease (CAD). This retrospective single-center analysis included 132 vessels in 77 patients who underwent CT angiography, myocardial perfusion imaging (MPI), and invasive FFR. The correlation coefficient between CT-FFR and invasive FFR and optimal cut-off value for CT-FFR to identify invasive FFR ≤ 0.8 were evaluated. The diagnostic accuracies of CT- FFR, and MPI were evaluated using an area under the receiver-operating characteristic curve (AUC) with invasive FFR as a reference standard. Diagnostic performance of CT-FFR was also evaluated concerning lesion characteristics, including intermediate lesions, left main lesions, tandem lesions, and/or diffuse lesions, and coronary calcium (Agatston score over 400). The Receiver Operating Characteristic curve analysis showed that the optimal cut-off value of CT-FFR for detecting invasive FFR ≤ 0.80 was 0.80 [AUC = 0.83, 95%CI: 0.76-0.90). Diagnostic sensitivity, specificity, positive and negative predictive value, and accuracy of CT-FFR when compared with those of MPI regarding per-patient analysis were 93% vs. 63%, 48% vs. 61%, 81% vs. 79%, 73% vs. 41%, and 79% vs. 62%, respectively, and for per-vessel analysis were 89% vs. 24%, 66% vs. 82%, 75% vs. 61%, 83% vs. 48%, and 78% vs. 51%, respectively. The AUC of the CT-FFR was significantly higher than MPI (0.83 vs. 0.57, p < 0.0001) regarding the per-vessel analysis. No differences in the diagnostic performance of CT-FFR were noted in the presence of intermediate lesions, left main lesions, tandem lesions, and/or diffuse lesions, and severe coronary calcium. On-site CT-FFR delivered a higher diagnostic performance than MPI for detecting CAD with invasive FFR ≤ 0.8, indicating the potential of CT-FFR as the gatekeeper of invasive coronary angiogram as well as percutaneous coronary intervention.