Accuracy of CT-derived interarterial and intramural anomalous coronary arteries anatomy compared with 3D-reconstructed IVUS in-vivo reference

In anomalous aortic origin of a coronary artery (AAOCA), coronary CT angiography (CCTA) is the primary tool for anatomical assessment. However, CCTA measurements lack validation against a high-resolution in-vivo standard. To assess CCTA reliability for lumen dimensions and intramural length (IML) in AAOCA, and to validate these against a three-dimensionally reconstructed intravascular ultrasound (3D-IVUS) reference using three additional IML methodologies. A total of 60 AAOCA patients with an interarterial/intramural course underwent both CCTA and IVUS. A 3D-IVUS was constructed and its geometric reproducibility assessed. CCTA reliability and agreement with 3D-IVUS were evaluated for ostial dimensions, position-dependent minimal lumen area (MLA), and IML, measured by interluminal space thickness (ILS), elliptic ratio, and pericoronary fat sign. 3D-IVUS reference standard showed excellent geometric reproducibility (median point-wise distance 0.19 mm, 95%CI 0.07–0.43 mm) and good-to-excellent intrareader reliability (ICC 0.72–0.96). CCTA intra- and inter-reader reliability was moderate-to-excellent for ostial parameters and ILS-derived IML (ICC 0.69–0.92) and poor-to-good for MLA (ICC 0.28–0.87). Against 3D-IVUS, CCTA ostial area demonstrated moderate correlation ( r = 0.73, p < 0.001) with minimal bias, and ILS-derived IML showed moderate agreement ( r = 0.59; bias + 0.23 mm), while the fat sign substantially overestimated length (+ 7.88 mm). Using 3D-IVUS as an in-vivo reference standard for the precise assessment of coronary anatomy in AAOCA, CCTA provided reproducible ostial measurements, and the ILS-based method showed the best performance among the evaluated CCTA approaches for estimating intramural length. However, wide limits of agreement preclude precise individual sizing, and position-dependent MLA measurements remain unreliable. 60 patients with interarterial/intramural AAOCA (2 L-AAOCA, 58 R-AAOCA; mean age 53 ± 12 years, 30% female) underwent both CCTA and IVUS. IVUS pullbacks were used to construct a 3D reference model, from which ostial dimensions, minimal lumen area (MLA), and intramural (IM) length were automatically extracted at four anatomically defined landmarks (distal reference, end of intramural segment, MLA, ostium) and compared with corresponding CCTA measurements analyzed per current clinical standards. Reliability of 3D-IVUS and CCTA measurements was assessed by intraclass correlation coefficient (ICC); agreement between modalities was assessed by Bland-Altman analysis. Both modalities showed high reproducibility for ostial area (ICC 0.93 for IVUS, 0.87 for CCTA), whereas agreement between CCTA and 3D-IVUS was more variable across parameters, with the widest limits of agreement for IM length and MLA-related measurements. Abbreviations: AAOCA = Anomalous aortic origin of a coronary artery-AAOCA = Left anomalous aortic origin of a coronary artery, R-AAOCA = Right anomalous aortic origin of a coronary artery, CCTA = Coronary computed tomography angiography, IVUS = intravascular ultrasound, 3D-IVUS = three-dimensionally reconstructed IVUS, IM = intramural, MLA, minimal lumen area, ICC = intraclass correlation coefficient, Dist Ref, distal reference lumen, End IM = end of intramural course.