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Coronary computed angiography (CCTA) with non-invasive fractional flow reserve (FFR) calculates lesion-specific ischemia when compared with invasive FFR and can be considered for patients with stable chest pain and intermediate-grade stenoses according to recent guidelines. The objective of this study was to compare a new CCTA-based artificial-intelligence deep-learning model for FFR prediction (FFR AI ) to computational fluid dynamics CT-derived FFR (FFR CT ) in patients with intermediate-grade coronary stenoses with FFR as reference standard. The FFR AI model was trained with curved multiplanar-reconstruction CCTA images of 500 stenotic vessels in 413 patients, using FFR measurements as the ground truth. We included 37 patients with 39 intermediate-grade stenoses on CCTA and invasive coronary angiography, and with FFR CT and FFR measurements in this retrospective proof of concept study. FFR AI was compared with FFR CT regarding the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy for predicting FFR ≤ 0.80. Sensitivity, specificity, PPV, NPV, and diagnostic accuracy of FFR AI in predicting FFR ≤ 0.80 were 91% (10/11), 82% (23/28), 67% (10/15), 96% (23/24), and 85% (33/39), respectively. Corresponding values for FFR CT were 82% (9/11), 75% (21/28), 56% (9/16), 91% (21/23), and 77% (30/39), respectively. Diagnostic accuracy did not differ significantly between FFR AI and FFR CT (p = 0.12). FFR AI performed similarly to FFR CT for predicting intermediate-grade coronary stenoses with FFR ≤ 0.80. These findings suggest FFR AI as a potential non-invasive imaging tool for guiding therapeutic management in these stenoses., (© 2024. The Author(s).)

Only one-third of intermediate-grade coronary artery stenosis (i.e. 40-70% diameter narrowing) causes myocardial ischemia, requiring most often additional invasive work-up with invasive fractional flow reserve (FFR). To evaluate the correlations between FFR estimates derived from computed tomography (FFR CT ) and adenosine perfusion cardiac magnetic resonance (CMR) with invasive FFR in intermediate-grade stenosis. Thirty-seven patients (mean age 61 ± 9 years; 25 men) who underwent adenosine perfusion CMR, quantitative coronary angiography and FFR in the work-up for intermediate-grade stenoses (n = 39) diagnosed at coronary CT angiography were retrospectively evaluated. Blinded FFR CT analysis was computed on each intermediate-grade lesion and correlated to the FFR values. On adenosine CMR, subendocardial time-enhancement maximal upslopes, normalized by respective left ventricle cavity upslopes, were obtained distal to a coronary stenosis (RISK area) and in remote myocardium (REMOTE area). The perfusion was subsequently assessed without (uncorrected RISK) and after correction for remote perfusion (relative myocardial perfusion index = REMOTE/RISK ratio), and then correlated to the FFR values. Differences in correlations were tested with z statistics and considered statistically significant different at a p < 0.05 level. The average FFR value was 0.85 ± 0.10 (0.60-0.98 range), 28% (n = 11) was ≤ 0.80. FFR value correlated poorly with uncorrected RISK upslopes (r = 0.151; p = 0.36), but equally strongly with FFR CT (r = 0.675; p < 0.001) and the relative myocardial perfusion index (r = - 0.63) (p < 0.001; z = 6.72) for assessment of lesion-specific ischemia. Both FFR CT and adenosine perfusion CMR strongly correlate with invasive FFR measurements for intermediate-grade stenosis. These preliminary findings pave the way for further studies evaluating non-invasively intermediate coronary stenosis in clinical practice.

Fractional flow reserve (FFR) during invasive coronary angiography has become an established tool for guiding treatment. However, only one-third of intermediate-grade coronary artery stenosis (ICAS) are hemodynamically significant and require coronary revascularization. Additionally, the severity of stenosis visually established by coronary computed tomography angiography (CCTA) does not reliably correlate with the functional severity. Therefore, additional angiographic morphologic descriptors affecting hemodynamic significance are required. To evaluate quantitative stenosis analysis and plaque descriptors by CCTA in predicting the hemodynamic significance of ICAS and to compare it with quantitative catheter coronary angiography (QCA). QCA was performed in 65 patients (mean age 63 ± 9 years; 47 men) with 76 ICAS (40-70%) on CCTA. Plaque descriptors were determined including circumferential extent of calcification, plaque composition, minimal lumen diameter (MLD) and area, diameter stenosis percentage (Ds %), area stenosis percentage and stenosis length on CCTA. MLD and Ds % were also analyzed on QCA. FFR was measured on 52 ICAS lesions on CCTA and QCA. The diagnostic values of the best CCTA and QCA descriptors were calculated for ICAS with FFR ≤ 0.80. Of the 76 ICAS on CCTA, 52 (68%) had a Ds % between 40 and 70% on QCA. Significant intertechnique correlations were found between CCTA and QCA for MLD and Ds % (p < 0.001). In 17 (33%) of the 52 ICAS lesions on QCA, FFR values were ≤ 0.80. Calcification circumference extent (p = 0.50) and plaque composition assessment (p = 0.59) did not correlate with the hemodynamic significance. Best predictors for FFR ≤ 0.80 stenosis were ≤ 1.35 mm MLD (82% sensitivity, 66% specificity), and ≤ 2.3 mm(²) minimal lumen area (88% sensitivity, 60% specificity) on CCTA, and ≤ 1.1 mm MLD (59% sensitivity, 77% specificity) on QCA. Quantitative CCTA and QCA poorly predict hemodynamic significance of ICAS, though CCTA seems to have a better sensitivity than QCA. In this range of stenoses, additional functional evaluation is required.