Numerical modeling of residual type B aortic dissection: longitudinal analysis of favorable and unfavorable evolution

Abstract

Residual type B aortic dissection was numerically investigated to highlight the contribution of biomechanical parameters to the pathology's evolution. Patient-specific geometries from cases involving both favorable and unfavorable evolution were modeled to assess their hemodynamic features. This original approach was supported by a longitudinal study confirming the association between morphological changes, hemodynamic features, adverse clinical outcomes, and CT-angioscan observations on the same patient. Comparing one patient with unfavorable evolution with one with favorable one, we identify potential biomechanical indicators predictive of unfavorable evolution: (i) a patent false lumen with a flow rate above 50% of inlet flow rate; (ii) high wall shear stress above 18 Pa at entry tears, and above 10 Pa at some regions of the false lumen wall; (iii) low time-averaged wall shear stress in distal false lumen below 0.5 Pa; (iv) vortical structure dynamics. Although these comparisons could only be conducted on 2 patients and need to be confirmed by a larger number of cases, our findings point to these hemodynamic markers as possible candidates for early evaluation of the pathology's evolution towards an unfavorable scenario.

Non-invasive estimation of the parameters of a three-element windkessel model of aortic arch arteries in patients undergoing thoracic endovascular aortic repair

“…The advantage of this strategy is that an iterative optimization process is not needed once the flow rate and pressure waveforms are available. A recent study did not use any Frontiers in Bioengineering and Biotechnology frontiersin.org patient-specific information to estimate the parameters (Fatma et al, 2022). Instead, a pressure waveform was obtained from the literature; a series of CFD simulations were performed to update the flow rate and pressure waveforms at the outlets, which were then used to optimize the Windkessel model parameters in Matlab.…”

On the role of tissue mechanics in fluid–structure interaction simulations of patient‐specific aortic dissection

“…In the context of vascular flow, prominent choices are the Quemada, 21 Carreau-Yasuda, 13,16,18,42 or the Carreau 31 model, capturing the shear-thinning behavior of blood. The latter rheological law can be expressed as…”

“…The generalized Newtonian fluid models employed in this work are characterized by a variable viscosity $$$ {\mu}_f={\mu}_f\left(\dot{\gamma}\right) $$$, which is a function of the shear rate $$$ \dot{\gamma} $$$, that is, $$$$ \dot{\gamma}:= 1/2\sqrt{\nabla^s\boldsymbol{u}:{\nabla}^s\boldsymbol{u}},\kern2em \mathrm{with}\kern2em {\nabla}^s\boldsymbol{u}:= 1/2\left(\nabla \boldsymbol{u}+\nabla {\boldsymbol{u}}^{\mathrm{T}}\right), $$$$ such that the Cauchy stress tensor can be expressed as $$$$ {\boldsymbol{\sigma}}_f:= -p\boldsymbol{I}+2{\mu}_f{\nabla}^s\boldsymbol{u}. $$$$ In the context of vascular flow, prominent choices are the Quemada, 21 Carreau‐Yasuda, 13,16,18,42 or the Carreau 31 model, capturing the shear‐thinning behavior of blood. The latter rheological law can be expressed as …”

Volume Analysis to Predict the Long-Term Evolution of Residual Aortic Dissection after Type A Repair

“…Hemodynamic factors are also important to predict the long term evolution of a RAD [ 27 , 28 ] and improve the understanding of this complex pathology. In a recent study [ 29 ], we developed a numerical patient-specific modeling of a RAD and we performed a hemodynamic analysis on two patients. Although these comparisons could only be conducted on two patients and need to be confirmed by a larger number of cases, our findings point to these hemodynamic markers as possible candidates for an early evaluation of the pathology’s evolution towards an unfavorable scenario.…”