Patient-specific requirements and clinical validation of MRI-based pressure mapping: A two-center study in patients with aortic coarctation.

Background Invasive peak-to-peak pressure gradients are the current clinical reference standard for assessing aortic coarctation. To obtain them, patients need to undergo arterial heart catheterization. Unless an intervention is performed, the procedure remains purely diagnostic, while the concomitant risks remain. Purpose To validate MRI-based pressure mapping against pressure drop derived from heart catheterization and to define minimal clinical requirements. Study Type Prospective clinical validation study. Population Twenty-seven coarctation patients with an indicated heart catheterization were enrolled at two clinical centers. MRI Sequences 1.5T including 4D velocity-encoded MRI and 3D anatomical imaging of the aorta. Assessment Pressure drop across the stenosis was calculated by pressure mapping based on the pressure Poisson equation. Calculated pressure drops were compared with catheter measured data. Spatial and temporal resolution were analyzed using in silico phantom-based data as well as in vivo measurements. Statistics Pressure drop was compared to peak-to-peak measurements. A two-sample paired mean equivalence test was used. Results In patients without imaging artifacts and a required spatial resolution >= 5 voxel/diameter, significant equivalence of pressure mapping compared to heart catheterization was found (17.5 +/- 6.49 vs. 16.6 +/- 6.53 mmHg, P < 0.001). Data Conclusion Pressure mapping provides equivalent accuracy to pressure drop obtained from heart catheterization in patients 1) without previous stenting and 2) with sufficient spatial image resolution (at least 5 voxels/diameter). In these patients the method can reliably be performed prior to the actual procedure, and thus allows safe noninvasive treatment planning based on MRI. Level of Evidence: 2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;49:81-89.