In this retrospective, single-center study, 28 patients (25 male, 3 female, median age 68 years) with obstructive coronary artery stenosis with a CAD RADS Score of 3 or 4a who underwent PCCT-CCTA and ICA were included.

All patients were scanned on the novel first-generation whole-body dual-source PCCT system (NAEOTOM Alpha, Siemens Healthcare GmbH, Forchheim Germany) using a prospective electrocardiogram gated sequential mode with 120 kV. The contrast-enhanced angiographic scan was reconstructed with a slice thickness of 0.6 mm, an increment of 0.4 mm, a soft tissue kernel of Bv40, a matrix size of 512 x 512, and a quantum iterative reconstruction level of 3. These reconstructions were used for on-site CT-FFR analysis (Frontier cFFR analysis, syngo.via Siemens Healthcare GmbH, Forchhei, Germany). Delta CT-FFR was calculated for each lesion by subtracting CT-FFR values 1.8 cm before and after the stenosis, a cut-off value of ≥ 0.06 indicated hemodynamic significance. Figure 1 outlines the workflow analysis.

Revascularization during ICA defined a stenosis as hemodynamically significant; the degree of stenosis was estimated visually by a senior cardiologist according to the American Heart Association guidelines (7) and classified analogously to the CAD RADS system for better comparability (8).

Sensitivity, specificity, negative and positive predictive value, and diagnostic accuracy of Delta CT-FFR have been determined. Patients were followed up to evaluate the rate of MACE six months after the CCTA.