Marleen Vonder, Abstract Co-Author: Nothing to Disclose

Kelly Jarvis, Presenter: Nothing to Disclose

Susanne Schnell, Abstract Co-Author: Nothing to Disclose

Michael Markl PhD, Abstract Co-Author: Nothing to Disclose

Joshua D Robinson MD, Abstract Co-Author: Nothing to Disclose

Cynthia Karfias Rigsby MD, Abstract Co-Author: Nothing to Disclose

Bradley D. Allen MD, Abstract Co-Author: Nothing to Disclose

Alex Barker, Abstract Co-Author: Nothing to Disclose

Pulmonary artery (PA) stenosis either at the anastomosis or in the branch PAs is the most common complication leading to intervention after the arterial switch operation (ASO) for D-transposition of the great arteries (DTGA). Accurately depicting PA stenosis is paramount for postop DTGA evaluation. 2D PC MRI (2D PC) or Doppler echo (echo) rely on velocity quantification in a single imaging plane and one-directional velocity encoding and may not detect the peak velocity across entire vessel segments. 4D flow provides 3-directional velocity encoding and full volumetric coverage of the great arteries and may improve hemodynamic evaluation. Our aim was to compare peak velocities measured by 2D PC and 4D flow with the gold standard echo in patients with DTGA s/p ASO.

Eleven patients with DTGA s/p ASO who underwent 2D PC and 4D flow were included (mean age 13.2 y (range 1-30)). Peak velocities were measured in the ascending aorta (AAo), main (MPA), right (RPA), and left (LPA) pulmonary arteries. Echo data was available in 10/8/5/4 patients in the AAo/MPA/RPA/LPA. Peak velocities were measured with: 1) a single cross section for 2D PC, 2) velocity maximum intensity projections (MIPs) of the entire aorta and PAs for 4D flow and 3) spectral Doppler for echo.

Significantly higher peak velocities were found with 4D flow than 2D PC in the AAo (1.27±0.37m/s vs 1.11±0.24m/s, p=0.021), MPA (2.22±1.17m/s vs 1.34±0.54m/s, p=0.006), RPA (2.20±0.67m/s vs 1.63±0.65m/s, p=0.026) and LPA (2.14±0.73m/s vs 1.64±0.69m/s, p=0.003) indicating the potential of 4D flow to provide improved stenosis assessment. Correlation analysis showed moderate to strong relationships between 4D and 2D PC in the AAo (R2=0.624), MPA (R2=0.696), RPA (R2=0.301) and LPA (R2=0.757) but consistent velocity underestimation by 2D PC (slopes of linear regression =0.38 - 0.82). No difference in peak velocity was found between 4D flow and echo for all vessels.

4D flow assessment of peak velocities in DTGA s/p ASO was similar to echo and superior to 2D PC which consistently underestimated peak velocities.

Improved assessment of peak pulmonary artery velocities using 4D flow velocity MIPs in DTGA s/p ASO may more accurately depict significant stenoses.

Vonder, M, Jarvis, K, Schnell, S, Markl, M, Robinson, J, Rigsby, C, Allen, B, Barker, A, 4D Flow MRI Improves Hemodynamic Evaluation in Patients with D-transposition of the Great Arteries Following the Arterial Switch Operation Compared to 2D Phase Contrast MRI and Doppler Echocardiography.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14006133.html