Comparison of non-contrast cardiovascular magnetic resonance imaging to computed tomography angiography for aortic annular sizing before transcatheter aortic valve replacement

BACKGROUND: Accurate measurement of aortic annulus is crucial before transcatheter aortic valve replacement (TAVR). Computed tomography (CT) angiography is the most commonly utilized method, but requires contrast administration. Cardiovascular magnetic resonance (CMR) imaging is a promising alternative modality to provide aortic annulus measurements. Few studies have compared the clinical feasibility and accuracy of non-contrast CMR to contrast-enhanced computed tomography (CT) angiography in order to provide a non-contrast alternative to CT annular sizing. METHODS: Twenty-one consecutive patients (mean age, 85.7 ± 5.2 years) with severe aortic stenosis (mean aortic valve area, 0.6 ± 0.1 cm²) underwent pre-TAVR CT angiography and a non-contrast CMR at 1.5 T. CT measurements were performed during systole as the clinical non-invasive standard. CMR measurements were performed during systole and diastole and included three-dimensional (3D) and two-dimensional (2D) methods. Interobserver differences were assessed using intraclass correlation. We recorded scan time in each patient. RESULTS: The mean systolic annular area was not significantly different between CT and 3D-CMR (480.0 ± 77.9 mm² vs 479.4 ± 66.2 mm²; P≤.98) in systole. There was no clinically relevant systematic difference between area measurements [mean difference, 0.6 mm²; limits of agreement -38.2 mm²; 39.3 mm²] using Bland-Altman analyses. Interobserver correlation was excellent. The diagnostic systolic 3D-CMR annular sizing scan was achieved in 4.4 ± 2.7 min. CONCLUSION: Non-contrast CMR protocol for the measurement of aortic annulus area is feasible and accurate. 3D-CMR could provide an alternative for annular sizing pre-TAVR assessment in patients who cannot undergo contrast-enhanced CT studies.