Diagnostic Efficacy and Safety of Low-Contrast-Dose Dual-Energy CT in Patients With Renal Impairment Undergoing Transcatheter Aortic Valve Replacement

Abstract

Objective: This study aimed to evaluate the diagnostic efficacy and safety of low-contrast-dose, dual-source dual-energy CT before transcatheter aortic valve replacement (TAVR) in patients with compromised renal function.

Materials and methods: A total of 54 consecutive patients (female:male, 26:38; 81.9 ± 7.3 years) with reduced renal function underwent pre-TAVR dual-energy CT with a 30-mL contrast agent between June 2022 and March 2023. Monochromatic (40- and 50-keV) and conventional (120-kVp) images were reconstructed and analyzed. The subjective quality score, vascular attenuation, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) were compared among the imaging techniques using the Friedman test and post-hoc analysis. Interobserver reliability for aortic annular measurement was assessed using the intraclass correlation coefficient (ICC) and Bland-Altman analysis. The procedural outcomes and incidence of post-contrast acute kidney injury (AKI) were assessed.

Results: Monochromatic images achieved diagnostic quality in all patients. The 50-keV images achieved superior vascular attenuation and CNR (P < 0.001 in all) while maintaining a similar SNR compared to conventional CT. For aortic annular measurement, the 50-keV images showed higher interobserver reliability compared to conventional CT: ICC, 0.98 vs. 0.90 for area and 0.97 vs. 0.95 for perimeter; 95% limits of agreement width, 0.63 cm² vs. 0.92 cm² for area and 5.78 mm vs. 8.50 mm for perimeter. The size of the implanted device matched CT-measured values in all patients, achieving a procedural success rate of 92.6%. No patient experienced a serum creatinine increase of ≥ 1.5 times baseline in the 48-72 hours following CT. However, one patient had a procedural delay due to gradual renal function deterioration.

Conclusion: Low-contrast-dose imaging with 50-keV reconstruction enables precise pre-TAVR evaluation with improved image quality and minimal risk of post-contrast AKI. This approach may be an effective and safe option for pre-TAVR evaluation in patients with compromised renal function.

Keywords: Aortic valve stenosis; Computed tomography angiography; Contrast media; Monochromatic; Transcatheter aortic valve replacement.

Fig. 1. Study participants. Of 66 patients who underwent pre-TAVR CT with 30 mL contrast media between June 2022 and March 2023, we excluded those with a history of aortic valve replacement, those who did not undergo the TAVR procedure, those who had single-energy cardiac CT scans, and those without delayed aortoiliac CT scans. As a result, our analysis included 54 patients. The number of patients included in each analysis is described. TAVR = transcatheter aortic valve replacement, CAD = coronary artery disease, ICA = invasive coronary angiography

Fig. 2. Examples of 40-keV, 50-keV, and conventional CT images, presented in the axial double-oblique view for the measurement of the aortic valve opening area (top) and annulus (middle), and the coronal oblique view (bottom). The monochromatic images exhibit superior vascular opacification and contrast-to-noise ratio compared to conventional images. However, at 40-keV, increased noise and blooming artifacts are observed due to aortic valve calcium. The 50-keV images demonstrate adequate contrast enhancement with reduced levels of noise and artifacts.