Noninvasive 4D Pressure Difference Mapping Derived from 4D Flow MRI in Patients with Repaired Aortic Coarctation: Comparison with Young Healthy Volunteers

Purpose: To assess spatial and temporal pressure changes in patients with repaired aortic coarctation compared with young healthy volunteers using 4D flow MRI and derived 4D pressure difference maps.

Methods: 4D flow MRI of the thoracic aorta was performed at 1.5 T in 13 patients after aortic coarctation repair without recoarctation (mean age: 18.8 years, 5 female, 8 male) and 13 healthy volunteers (mean age: 22.9 years, 4 female, 9 male). 4D pressure difference maps were computed based on the Navier-Stokes equation. The thoracic aorta was divided into four segments: ascending aorta, aortic arch, proximal descending aorta, and distal descending aorta.

Results: Mean spatial pressure range at mid systole for patients/volunteers was (in mm Hg): ascending aorta 1.8/1.6 (p= ns), arch 4.8/1.7 (p= 0.02), proximal descending 8.9/1.6 (p < 0.001), and distal descending 2.8/1.6 (p= 0.002). Spatial pressure profiles along the aortic centerline demonstrated pressure gradients in patients affecting both aortic arch and proximal descending aorta. Mean maximum slope of local pressure amplitudes for patients/volunteers was (in mm Hg/cm): ascending aorta 7.4/2.5 (p= ns), arch 6.6/2.1 (p < 0.001), proximal descending 12.1/1.9 (p= 0.002), and distal descending 3.9/2.1 (p= 0.002).

Conclusion: Noninvasive 4D pressure difference mapping derived from 4D flow MRI showed significant spatial and temporal changes in patients with repaired aortic coarctation compared with young healthy volunteers, particularly affecting aortic arch and proximal descending aorta, but also distal descending aorta. The technique can characterize such changes not only noninvasively but also in great detail.