Slice positioning in phase-contrast MRI impacts aortic stenosis assessment

Area of Science:

• Cardiovascular Imaging
• Cardiac MRI
• Aortic Stenosis Assessment

Background:

• Accurate measurement of aortic valve area (AVA) is crucial for managing aortic stenosis (AS).
• Phase-contrast cardiovascular magnetic resonance imaging (PC-CMR) is a non-invasive tool for assessing AS severity.
• Determining the optimal slice position for PC-CMR is essential for reliable AVA measurements.

Purpose of the Study:

• To identify the optimal slice-position of PC-CMR above the leaflet-attachment plane (LAP) for accurate flow-velocity, flow-volume, and AVA measurements in AS patients.
• To compare PC-CMR derived measurements with invasive and echocardiographic data.

Main Methods:

• Fifty-five patients with moderate/severe AS underwent cardiac catheterization, transthoracic echocardiography (TTE), and PC-CMR.
• PC-CMR image planes were acquired parallel to the LAP, ranging from 22 mm below to 24 mm above.
• AVA was calculated using PC-CMR by dividing systolic flow-volume by peak-velocity; stroke volume (SV) and AVA were compared to volumetric and invasive methods.

Main Results:

• PC-CMR stroke volume showed strong correlation with volumetry (rho: 0.633) and was independent of slice position above LAP.
• AVA measurements in planes 0-10 mm above LAP significantly overestimated invasive AVA (MMD: -0.14 cm²).
• AVA measurements between 10-20 mm above LAP showed good agreement with invasive determination (MMD: 0.003 cm²), with the plane 15 mm above LAP yielding the lowest bias.

Conclusions:

• PC-CMR measurements at 0-10 mm above LAP should be avoided for AVA assessment in AS due to significant overestimation compared to invasive methods.
• AVA assessment by PC-CMR between 10-20 mm above LAP demonstrates good agreement with invasive measurements.
• A slice position 15 mm above the LAP provides the most accurate AVA assessment by PC-CMR in patients with AS.