Importance of imaging-acquisition protocol and post-processing analysis for extracellular volume fraction assessment by computed tomography.

Background: Computed tomography angiography (CTA) assessment of myocardial extracellular volume fraction (CT-ECV) is feasible, although the protocols for imaging acquisition and post-processing methodology have varied. We aimed to identify a pragmatic protocol for CT-ECV assessment encompassing both imaging acquisition and post-processing methodologies to facilitate its clinical implementation.
Methods: We evaluated consecutive patients with severe aortic stenosis undergoing evaluation for transcatheter aortic valve replacement (TAVR). Pre-contrast and 3-min-delayed CTA were obtained in systole using either helical prospective-ECG-triggered (high-pitch) or axial sequential-ECG-gated acquisition, adding to standard TAVR CTA protocol. Using a dedicated software for co-registration of CTA datasets, three methodologies for ECV measurement were evaluated: (1) mid-septum region of interest (Septal ECV), (2) averaged-global ECV (Global ECV) encompassing 16-AHA segments, and (3) average of septal and lateral segments (Averaged ECVsep and Averaged ECVlat).
Results: Among the 142 patients enrolled (median ​= ​81 years, 44% females), 8 were excluded due to significant imaging artifacts precluding Global ECV assessment. High-pitch scan mode was performed in 68 patients (48%). Suboptimal image quality for Global ECV assessment was associated with high-pitch scan mode (odds ratio: OR ​= ​2.26, p ​= ​0.036), along with the presence of intracardiac leads (OR ​= ​4.91, p ​= ​0.002), and BMI≥35 ​kg/m ² (OR ​= ​2.80, p ​= ​0.026). Septal ECV [median ​= ​29.4%] and Averaged ECVsep [29.0%] were similar (p ​= ​0.108), while Averaged ECVlat [27.5%] was lower than Averaged ECVsep (p ​< ​0.001), resulting in lower Global ECV [28.6%].
Conclusions: Myocardial CT-ECV assessment is feasible using a systolic sequential acquisition pre-contrast, and similar additional 3-min delayed scan. Septal ECV measurement provides similar values to Global ECV and is equally reproducible.
Competing Interests: Declaration of competing interest Dr. Cavalcante has received consulting fees from 4C, Abbott Structural, Anteris, AriaCV, Boston Scientific, Edwards Lifesciences, Medtronic, VDyne, WL Gore, Xylocor; has received research grant support from Abbott Northwestern Hospital Foundation. Dr. Enriquez-Sarano has received consulting fees from Cryolife, Edwards Lifescience, Highlife, and ChemImage. Dr. Sorajja has received consulting fees from Abbott Structural, Anteris, Boston Scientific, EvolutionMed, Medtronic, Shifamed, vDyne, and WL Gore; has received research grant support from Abbott Structural, Medtronic and Boston Scientific, and has been a speaker for Abbott Structural. The remaining authors have nothing to disclosure.
(Copyright © 2023 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.)