Background: Coronary artery disease and severe (AS) frequently coexist. Computed tomography angiography (CT) and invasive coronary angiography (ICA) are used for planning of transcatheter aortic valve implantation (TAVI) in patients with AS. Recently, the utilization of CT with additional assessment of plaque morphology, perivascular Inflammation with peri-coronary adipose tissue (PCAT) density and hemodynamic function with CT-fractional flow reserve (CT-FFR) have been introduced. However, data regarding the diagnostic yield of these methods to identify functional ischemia in patients with AS are sparse. This study investigates the diagnostic performance of these methods compared to ICA with resting full-cycle ratio (RFR) as a reference physiological index in patients with AS.  

Materials and Methods: We retrospectively enrolled 87 patients with 95 lesions who underwent an electrocardiogram-gated CT for TAVI planning and ICA with RFR assessment. Anatomical CT quantification, plaque morphology and PCAT density assessment were performed using dedicated software (Medis Suite CT Plaque Analysis, Medis, Leiden, Netherlands) and CT-FFR analysis was calculated using prototype software (cFFR version 3.0, Siemens Healthineers, Erlangen, Germany).

Results: The mean patient age was 77.7±7.4 years, 38 % were female and median body mass index was 26.1 kg/m² [interquartile range (IQR):  24.1 to 29.7 kg/m²]. The mean aortic transvalvular gradient was 45.9±13.7 mmHg. The left anterior descending artery was the most commonly interrogated vessel (64%). Forty-two (44.2%) lesions were classified as functional significant by RFR (≤0.89) as the reference standard. CT-FFR showed an excellent diagnostic performance (area under the curve = 0.885, 95% CI 0.809–0.963, p < 0.001) in its ability to detect functional significant lesions, superior to anatomical, plaque morphology (i.e. necrotic core volume (NCV)) and PCAT assessment (Figure 1). Plaque composition  and PCAT were not significantly different in lesions with and without ischemia. Univariable and multivariable analysis revealed CT-FFR as the only predictor (OR: 1.28 (95% CI 1.17 to 1.43), p<0.001) for functional significant lesions. Overall, CT-FFR showed a diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of 88.4% (95%CI: 80.2%-94.1%), 78.5% (95%CI: 63.2%-89.7%), 96.2% (95%CI: 87.0%-99.5%), 94.3% (95%CI: 80.8%-99.3%) and 85.0% (95%CI: 73.4%-92.9%) to identify functional significant lesions.

Conclusion: CT-FFR was superior to CT anatomical, plaque morphology and PCAT assessment to detect functional significant stenosis in patients with AS.