In this work, the hemodynamics of a patient afflicted by aortic coarctation was investigated, integrating Computational Fluid-Dynamics simulations and Magnetic Resonance Imaging data. Starting from MR images, acquired as part of the clinical routine, it was possible to reconstruct the 3D geometry of the patient, both in pre and post-intervention cases. The patient-specific flow conditions were prescribed at the ascending aorta as the inlet boundary condition; 3-elements Windkessel models were the outlet boundary conditions. A sensitivity analysis of these parameters was carried out in a deterministic and stochastic way, with a final quantification of the uncertainty of an input parameter on the output of the simulations.