  Understanding the complex interplay between morphologic and hemodynamic
features in aortic dissection is critical for risk stratification and for the
development of individualized therapy. This work evaluates the effects of entry
and exit tear size on the hemodynamics in type B aortic dissection by comparing
fluid-structure interaction (FSI) simulations with in vitro 4D-flow magnetic
resonance imaging (MRI). A baseline patient-specific 3D-printed model and two
variants with modified tear size (smaller entry tear, smaller exit tear) were
embedded into a flow- and pressure-controlled setup to perform MRI as well as
12-point catheter-based pressure measurements. The same models defined the wall
and fluid domains for FSI simulations, for which boundary conditions were
matched with measured data. Results showed exceptionally well matched complex
flow patterns between 4D-flow MRI and FSI simulations. Compared to the baseline
model, false lumen flow volume decreased with either a smaller entry tear
(-17.8 and -18.5 %, for FSI simulation and 4D-flow MRI, respectively) or
smaller exit tear (-16.0 and -17.3 %). True to false lumen pressure difference
(initially 11.0 and 7.9 mmHg, for FSI simulation and catheter-based pressure
measurements, respectively) increased with a smaller entry tear (28.9 and 14.6
mmHg), and became negative with a smaller exit tear (-20.6 and -13.2 mmHg).
This work establishes quantitative and qualitative effects of entry or exit
tear size on hemodynamics in aortic dissection, with particularly notable
impact observed on FL pressurization. FSI simulations demonstrate acceptable
qualitative and quantitative agreement with flow imaging, supporting its
deployment in clinical studies.
