Endothelial shear stress computed from coronary computed tomography angiography: A direct comparison to intravascular ultrasound

Abstract

Introduction: Intravascular ultrasound (IVUS) studies have shown that biomechanical variables, particularly endothelial shear stress (ESS), add synergistic prognostic insight when combined with anatomic high-risk plaque features. Non-invasive risk assessment of coronary plaques with coronary computed tomography angiography (CCTA) would be helpful to enable broad population risk-screening.

Aim: To compare the accuracy of ESS computation of local ESS metrics by CCTA vs IVUS imaging.

Methods: We analyzed 59 patients from a registry of patients who underwent both IVUS and CCTA for suspected CAD. CCTA images were acquired using either a 64- or 256-slice scanner. Lumen, vessel, and plaque areas were segmented from both IVUS and CCTA (59 arteries, 686 3-mm segments). Images were co-registered and used to generate a 3-D arterial reconstruction, and local ESS distribution was assessed by computational fluid dynamics (CFD) and reported in consecutive 3-mm segments.

Results: Anatomical plaque characteristics (vessel, lumen, plaque area and minimal luminal area [MLA] per artery) were correlated when measured with IVUS and CCTA: 12.7 ​± ​4.3 vs 10.7 ​± ​4.5 ​mm², r ​= ​0.63; 6.8 ​± ​2.7 vs 5.6 ​± ​2.7 ​mm², r ​= ​0.43; 5.9 ​± ​2.9 vs 5.1 ​± ​3.2 ​mm², r ​= ​0.52; 4.5 ​± ​1.3 vs 4.1 ​± ​1.5 ​mm², r ​= ​0.67 respectively. ESS metrics of local minimal, maximal, and average ESS were also moderately correlated when measured with IVUS and CCTA (2.0 ​± ​1.4 vs 2.5 ​± ​2.6 ​Pa^, r ​= ​0.28; 3.3 ​± ​1.6 vs 4.2 ​± ​3.6 ​Pa, r ​= ​0.42; 2.6 ​± ​1.5 vs 3.3 ​± ​3.0 ​Pa, r ​= ​0.35, respectively). CCTA-based computation accurately identified the spatial localization of local ESS heterogeneity compared to IVUS, with Bland-Altman analyses indicating that the absolute ESS differences between the two CCTA methods were pathobiologically minor.

Conclusion: Local ESS evaluation by CCTA is possible and similar to IVUS; and is useful for identifying local flow patterns that are relevant to plaque development, progression, and destabilization.

Keywords: CCTA; Coronary computed tomography angiography; ESS; Endothelial shear stress; IVUS; Intravascular ultrasound.

Figure 1:

Study Flow Chart

Figure 2:. A1-A4: comparison of vascular features and ESS metrics by CCTA vs. IVUS. B1-B4: images 3D reconstruction and color-coded topographical map of the same patient.

CCTA= coronary computed tomography angiography, EEM = external elastic membrane, IVUS=intravascular ultrasound, ESS=endothelial shear stress, Plq Thick = plaque thickness

Figure 3:. Bland-Altman Plots of Minimal ESS by CCTA vs by IVUS for All CCTA Methods (Combined 256-slice and 64-slice methods)

CCTA= coronary computed tomography angiography IVUS=intravascular ultrasound Each marker (N=686) corresponds to average value over 0.3 mm thick sub segment Mean difference: Combined 256+64 slice CCTA: −0.50 Pa (CI −0.696 to −0.303) 256-slice CCTA: −0.23 Pa (CI −0.440 to −0.028) 64-slice CCTA: −0.75 Pa (CI −1.080 to −0.422)

Figure 4:. Bland-Altman Plots of Maximal ESS by CCTA vs by IVUS for All CCTA Methods (Combined 256-slice method and 64-slice methods)

CCTA= coronary computed tomography angiography IVUS=intravascular ultrasound Each marker (N=686) corresponds to average value over ~0.3 mm thick sub segment Mean difference: Combined 256+64-slice CCTA: −0.85 Pa (CI −1.094 to −0.601) 256-slice CCTA: −0.52 Pa (CI −0.759 to −0.288) 64-slice CCTA: −1.15 Pa (CI −1.579 to −0.731)

Figure 5:. Bland-Altman Plots of Average ESS by CCTA vs by IVUS for All CCTA methods (Combined 256- slice method and 64-slice method)

CCTA=coronary computed tomography angiography, IVUS=intravsacular ultrasound Each marker (N=686) corresponds to average value over ~0.3 mm thick sub segment Mean difference: Combined 256+64 slice CCTA: −0.67 Pa (CI −0.885 to −0.453) 256-slice CCTA: −0.37 Pa (CI −0.586 to −0.158) 64-slice CCTA: −0.95 Pa (CI −1.317 to −0.583)