  A data-driven Reduced Order Model (ROM) based on a Proper Orthogonal
Decomposition - Radial Basis Function (POD-RBF) approach is adopted in this
paper for the analysis of blood flow dynamics in a patient-specific case of
Atrial Fibrillation (AF). The Full Order Model (FOM) is represented by
incompressible Navier-Stokes equations, discretized with a Finite Volume (FV)
approach. Both the Newtonian and the Casson's constitutive laws are employed.
The aim is to build a computational tool able to efficiently and accurately
reconstruct the patterns of relevant hemodynamics indices related to the stasis
of the blood in a physical parametrization framework including the cardiac
output in the Newtonian case and also the plasma viscosity and the hematocrit
in the non-Newtonian one. Many FOM-ROM comparisons are shown to analyze the
performance of our approach as regards errors and computational speed-up.
