March 15, 2019Journal of Cardiovascular Translational ResearchOpen Access

Ex Vivo Pilot Study of Cardiac Magnetic Resonance Velocity Mapping for Quantification of Aortic Regurgitation in a Porcine Model in the Presence of a Transcatheter Heart Valve

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Why the study?

The accuracy of aortic regurgitation quantification by MR imaging in the presence of a transcatheter heart valve remains to be established.

Does cardiac MR velocity mapping accurately quantify aortic regurgitation in the presence of a transcatheter heart valve in an ex vivo porcine model?

Structured PICO

Does cardiac MR velocity mapping accurately quantify aortic regurgitation in the presence of a transcatheter heart valve in an ex vivo porcine model?

Population

Ex vivo porcine model (n=1) under steady flow conditions

Intervention

Cardiac magnetic resonance (MR) velocity mapping across two transcatheter heart valves (Edwards SAPIEN XT, Medtronic CoreValve)

Outcome

Accuracy, precision, and repeatability of antegrade flow (AF) and retrograde flow (RF) quantification, and optimal slice positionsurrogate

Cardiac MR velocity mapping is accurate and highly repeatable for quantifying aortic regurgitation in the presence of a transcatheter heart valve in an ex vivo model, provided the optimal slice position is used.

Limitations

Pilot study
Ex vivo setting
Requires confirmation in future clinical studies

Implication

MR velocity mapping accurately quantifies AR across THVs ex vivo when corrected; leaves open in vivo validation for post-TAVR assessment.

Abstract

Accuracy of aortic regurgitation (AR) quantification by magnetic resonance (MR) imaging in the presence of a transcatheter heart valve (THV) remains to be established. We evaluated the accuracy of cardiac MR velocity mapping for quantification of antegrade flow (AF) and retrograde flow (RF) across a THV and the optimal slice position to use in cardiac MR imaging. In a systematic and fully controlled laboratory ex vivo setting, two THVs (Edwards SAPIEN XT, Medtronic CoreValve) were tested in a porcine model (n = 1) under steady flow conditions. Results showed a high level of accuracy and precision. For both THVs, AF was best measured at left ventricular outflow tract level, and RF at ascending aorta level. At these levels, MR had an excellent repeatability (ICC > 0.99), with a tendency to overestimate (4.6 ± 2.4% to 9.4 ± 7.0%). Quantification of AR by MR velocity mapping in the presence of a THV was accurate, precise, and repeatable in this pilot study, when corrected for the systematic error and when the best MR slice position was used. Confirmation of these results in future clinical studies would be a step forward in increasing the accuracy of the assessment of paravalvular AR severity.