April 22, 2020European RadiologyOpen Access

Non-contrast MRI protocol for TAVI guidance: quiescent-interval single-shot angiography in comparison with contrast-enhanced CT

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Why the study?

The study evaluated unenhanced quiescent-interval single-shot MR angiography compared with contrast-enhanced computed tomography angiography to determine whether contrast-free guidance is feasible for transcatheter aortic valve intervention.

Does a non-contrast MRI protocol (QISS-MRA and 3D whole heart MRI) provide comparable measurements to contrast-enhanced CTA for TAVI guidance in patients referred for TAVI?

Structured PICO

Does a non-contrast MRI protocol (QISS-MRA and 3D whole heart MRI) provide comparable measurements to contrast-enhanced CTA for TAVI guidance in patients referred for TAVI?

Population

26 patients referred for transcatheter aortic valve intervention (TAVI) evaluation with severe aortic stenosis, mean age 83 ± 5 years, 58% female, 69% with impaired renal function (eGFR < 60 ml/min/1.73 m2).

Intervention

Non-contrast MRI protocol including quiescent-interval single-shot MR angiography (QISS-MRA) for aortoiliofemoral access guidance and 3D 'whole heart' MRI for prosthesis sizing on a 1.5-T system.

Comparator

Contrast-enhanced computed tomography angiography (CTA) for TAVI planning.

Outcome

Correlation and agreement of aortoiliofemoral vessel diameters, aortic root parameters, and inter-method decision for transfemoral access route between QISS-MRA and CTA.surrogate

A non-contrast MRI protocol using QISS-MRA and 3D whole heart MRI provides comparable access route and aortic root evaluation to contrast-enhanced CTA, offering a viable alternative for TAVI planning in patients with renal impairment.

Limitations

Small sample size
Limited image quality in the abdominopelvic region owing to motion and flow-related artifacts
QISS-MRA lacks visualization of calcified plaque burden as it depicts exclusively the vessel lumen

Implication

QISS-MRA may enable contrast-free TAVI access planning in renal impairment; supports larger validation trials before routine adoption.

Abstract

OBJECTIVES: To prospectively compare unenhanced quiescent-interval single-shot MR angiography (QISS-MRA) with contrast-enhanced computed tomography angiography (CTA) for contrast-free guidance in transcatheter aortic valve intervention (TAVI). METHODS: Twenty-six patients (mean age 83 ± 5 years, 15 female [58%]) referred for TAVI evaluation underwent QISS-MRA for aortoiliofemoral access guidance and non-contrast three-dimensional (3D) "whole heart" MRI for prosthesis sizing on a 1.5-T system. Contrast-enhanced CTA was performed as imaging gold standard for TAVI planning. Image quality was assessed by a 4-point Likert scale; continuous MRA and CTA measurements were compared with regression and Bland-Altman analyses. RESULTS: QISS-MRA and CTA-based measurements of aortoiliofemoral vessel diameters correlated moderately to very strong (r = 0.572 to 0.851, all p ≤ 0.002) with good to excellent inter-observer reliability (intra-class correlation coefficient (ICC) = 0.862 to 0.999, all p < 0.0001) regarding QISS assessment. Mean diameters of the infrarenal aorta and iliofemoral vessels differed significantly (bias 0.37 to 0.98 mm, p = 0.041 to < 0.0001) between the two modalities. However, inter-method decision for transfemoral access route was comparable (κ = 0.866, p < 0.0001). Aortic root parameters assessed by 3D whole heart MRI strongly correlated (r = 0.679 to 0.887, all p ≤ 0.0001) to CTA measurements. CONCLUSION: QISS-MRA provides contrast-free access route evaluation in TAVI patients with moderate to strong correlations compared with CTA and substantial inter-observer agreement. Despite some significant differences in minimal vessel diameters, inter-method agreement for transfemoral accessibility is strong. Combination with 3D whole heart MRI facilitates unenhanced TAVI guidance. KEY POINTS: • QISS-MRA and CTA inter-method agreement for transfemoral approach is strong. • QISS-MRA is a very good alternative to CTA and MRA especially in patients with Kidney Disease Outcomes Quality Initiativestages 4 and 5. • Combination of QISS-MRA and 3D "whole heart" MRI facilitates fully unenhanced TAVI guidance.