On the severity of aortic stenosis in ascending aortic aneurysm: A computational tool to examine ventricular-arterial interaction and aortic wall stress

doi:10.1016/j.mechrescom.2020.103621

Mechanics Research Communications

Volume 110, December 2020, 103621

https://doi.org/10.1016/j.mechrescom.2020.103621 Get rights and content

Highlights

•
Assess changes in hemodynamic and structural variables of stenotic ascending aortic aneurysms by 1D and 3D modeling tools.
•
Post-stenotic wall and shear stresses of aneurysmal aorta increase non-linearly with severity of aortic stenosis.
•
The increase in the shear and principal stresses with the aortic valve severity are relate to valvulo-arterial impedance.
•
Prediction of valvular-arterial impedance for stratifying chronic aortic aneurysms developing aortic stenosis during followup.

Abstract

An ascending thoracic aortic aneurysm (ATAA) is a life-threatening cardiovascular consequence of vessel dilatation that portends adverse events and death. From a clinical perspective, ATAA should not be treated as an isolated disease, and surgery is often carried out in the presence of AS, aortic insufficiency or a calcified valve leaflet. Aortic stenosis (AS) is common in ATAAs and leads to both vessel rigidity and left ventricular (LV) impairment. In this study, lumped-parameter modeling and computational analysis were used to assess the change in the wall shear stress (WSS) and intramural wall stress of patient-specific ATAA models with different degrees of AS (i.e., mild to severe). The ATAAs of four patients were reconstructed from imaging data and AS was simulated virtually using the lumped-based CircAdapt tool using clinical and echocardiographic data. Results show that LV work derived from pressure-volume loops increased with the severity of AS. Post-stenotic hemodynamic and structural variables markedly increased with AS severity, with WSS showing a 10-fold increase for the most severe AS model as compared to the baseline model with a well-functioning aortic valve. Most importantly, the increase in WSS and aortic wall stress was associated with pronounced values of valvulo-arterial impedance as an indicator of LV dysfunction. This study provides novel insights into progression of AS in patients with ATAAs at high risk of adverse events, and the potential value of valvulo-arterial impedance to predict changes in hemodynamic and structural parameters with the severity of AS.

Section snippets

1. Introduction

An ascending thoracic aortic aneurysm (ATAA) is a cardiovascular condition that leads to permanent dilatation of the vessel and a high risk of adverse events when aortic size is >5 cm [1]. Nearly 10 out of 100,000 persons per year are affected by ATAA [2], and in those with a bicuspid aortic valve (BAV), the prevalence of aortopathy ranges from 20 to 84% [3]. The risk of ATAA development in BAV patients was found to be 80-fold higher than for the general population with a morphologically-normal

2.1. ATAA segmentation and meshing

Computed tomography angiography (CTA) scans of four patients with ATAA were identified from radiologic records of ISMETT IRCCS hospital as reported in similar studies [20,21]. We selected two BAV ATAAs and two TAV ATAAs with aortic dilatation involving the ascending aorta (Type A) and the aortic root (Type N) [22]. BAV ATAAs were characterized by the right-left leaflet cusp fusion. For each patient, aortic valve function was assessed by Doppler echocardiography, with no signs of AS or AI. The

3. Results

Fig. 3 shows the pressure-volume loops predicted by the lumped-parameter model for each patient at different degrees of AS. A leftward shift of pressure-volume loops was observed as the AS increases from the baseline condition to the severe condition. The severity of AS augments total LV work, with blood pressure rising sharply during systole to a domed-shaped pressure-volume loop. SV tends to slightly reduce while valvulo-arterial impedance rises with stenosis severity.

Fig. 4 displays a

4. Discussion

We adopted a computational framework to assess the change in the hemodynamic and structural mechanics of ATAAs under different degrees of AS. The ventricular-arterial interaction modeling approach demonstrated that post-stenotic wall and shear stresses exerted on the ATAA increase non-linearly from the baseline configuration of a patient with no signs of valvulopathy to the virtual model with severe AS. Specifically, peak systolic WSS for the model with severe AS rose up to 10-fold with respect

5. Conclusion

In this study, simulations were performed to assess the impact of post-stenotic shear and wall stresses in patients with ATAAs. As the stenosis increased from the baseline model with no signs of valvular dysfunction to the virtual model with severe AS, the WSS and maximum principal stress shown a 2.5- and 6-fold increase on the forces exerted on the ATAA wall, respectively. Hemodynamic and structural changes were associated with predictions of the valvular-arterial impedance, suggesting LV

Declaration of Competing Interest

None.

Acknowledgment

This work was supported by a “Ricerca Finalizzata” grant from the Italian Ministry of Health (GR-2011-02348129) to Salvatore Pasta.

References (34)

J.A. Elefteriades et al.
Thoracic aortic aneurysm clinically pertinent controversies and uncertainties
J. Am. Coll. Cardiol.
(2010)
R.R. Davies et al.
Natural history of ascending aortic aneurysms in the setting of an unreplaced bicuspid aortic valve
Ann. Thorac. Surg.
(2007)
M.A. Borger et al.
The American Association for Thoracic Surgery consensus guidelines on bicuspid aortic valve-related aortopathy: full online-only version
J. Thorac. Cardiovasc. Surg.
(2018)
G. Raffa et al.
Patients with bicuspid aortic valve are likely to receive an aortic valve prosthesis during prophylactic resection of their ascending aortic aneurysm
Int. J. Cardiol.
(2016)
S. Pasta et al.
In silico shear and intramural stresses are linked to aortic valve morphology in dilated ascending aorta
Eur. J. Vasc. Endovasc. Surg.
(2017)
D.P. Nathan et al.
Increased ascending aortic wall stress in patients with bicuspid aortic valves
Ann. Thorac. Surg.
(2011)
A. Gomez et al.
Wall stress distribution in bicuspid aortic valve-associated ascending thoracic aortic aneurysms
Ann. Thorac. Surg.
(2020)
S. Pasta et al.
Shear stress and aortic strain associations with biomarkers of ascending thoracic aortic aneurysm
Ann. Thorac. Surg.
(2020)
A. Gallo et al.
On the prospect of serum exosomal miRNA profiling and protein biomarkers for the diagnosis of ascending aortic dilatation in patients with bicuspid and tricuspid aortic valve
Int. J. Cardiol.
(2018)
S. Pasta et al.
Constitutive modeling of ascending thoracic aortic aneurysms using microstructural parameters
Med. Eng. Phys.
(2016)

V. Agnese et al.

Patterns of ascending aortic dilatation and predictors of surgical replacement of the aorta: a comparison of bicuspid and tricuspid aortic valve patients over eight years of follow-up

J. Mol. Cell. Cardiol.

(2019)

G.M. Raffa et al.

Patients with bicuspid aortic valve are likely to receive an aortic valve prosthesis during prophylactic resection of their ascending aortic aneurysm

Int. J. Cardiol.

(2016)

A. Duprey et al.

Biaxial rupture properties of ascending thoracic aortic aneurysms

Acta Biomater.

(2016)

V. Mendez et al.

Comparison of hemodynamic and structural indices of ascending thoracic aortic aneurysm as predicted by 2-way FSI, CFD rigid wall simulation and patient-specific displacement-based FEA

Comput. Biol. Med.

(2018)

A. Rinaudo et al.

Biomechanical implications of excessive endograft protrusion into the aortic arch after thoracic endovascular repair

Comput. Biol. Med.

(2015)

S. Verma et al.

Aortic dilatation in patients with bicuspid aortic valve

N. Engl. J. Med.

(2014)

H.I. Michelena et al.

Bicuspid aortic valve: identifying knowledge gaps and rising to the challenge from the international bicuspid aortic valve consortium (BAVCon)

Circulation

(2014)

Cited by (7)

Evaluating uncertainties in CFD simulations of patient-specific aorta models using Grid Convergence Index method
2023, Mechanics Research Communications
Cardiovascular diseases are among the most important causes of global mortality. Computational Fluid Dynamics (CFD) is a powerful research tool that analyzes the hemodynamics of artery and blood flow patterns. In this study, CFD simulations are performed to assess the patient-specific healthy aorta, fusiform, and saccular aneurysm with various mesh types, including tetrahedral, polyhedral, and poly-hexacore. The aim of this study is to explore how different mesh types and grid densities impact the hemodynamic properties of physiological flows, with the goal of identifying the most cost-effective meshing approach. A mesh independence study is carried out to ensure the precision of the results, considering the wall shear stress distribution. For this, five different mesh resolutions are generated for each geometry. The uncertainties of the simulations associated with the discretization techniques and solutions are evaluated using the Grid Convergence Index (GCI) method. The findings showed that increasing the mesh density provides smaller uncertainty. GCI values for the wall shear stress are in the range of convergence, indicating that the results are reliable and accurate. Mesh type selection affects the accuracy and computational cost of our simulations. The polyhedral and poly-hexacore meshes lead to a good compromise between precision and computational cost, while the tetrahedral mesh style gives the most precise results with fluctuation. This work provides a systematic approach based on the Grid Convergence Index method in order to select the most appropriate mesh type for evaluating uncertainties in CFD simulations of patient-specific healthy aortas and aortas with abdominal aneurysms. According to the findings and GCI analysis, the polyhedral mesh type was chosen for all patient-specific aorta models. The study clearly demonstrated its superiority over other mesh types, considering uncertainties and computational costs associated with different mesh styles.
A review on the biomechanical behaviour of the aorta
2023, Journal of the Mechanical Behavior of Biomedical Materials
Large aortic aneurysm and acute and chronic aortic dissection are pathologies of the aorta requiring surgery. Recent advances in medical intervention have improved patient outcomes; however, a clear understanding of the mechanisms leading to aortic failure and, hence, a better understanding of failure risk, is still missing. Biomechanical analysis of the aorta could provide insights into the development and progression of aortic abnormalities, giving clinicians a powerful tool in risk stratification. The complexity of the aortic system presents significant challenges for a biomechanical study and requires various approaches to analyse the aorta. To address this, here we present a holistic review of the biomechanical studies of the aorta by categorising articles into four broad approaches, namely theoretical, in vivo, experimental and combined investigations. Experimental studies that focus on identifying mechanical properties of the aortic tissue are also included. By reviewing the literature and discussing drawbacks, limitations and future challenges in each area, we hope to present a more complete picture of the state-of-the-art of aortic biomechanics to stimulate research on critical topics. Combining experimental modalities and computational approaches could lead to more comprehensive results in risk prediction for the aortic system.
Aortic local biomechanical properties in ascending aortic aneurysms
2022, Acta Biomaterialia
Citation Excerpt :
It might explain our results: higher levels of aortic stenosis are associated with dilated aortas, as we have shown that the aortic wall stiffness was higher in the AsAAs associated with aortic stenosis than those without aortic stenosis. Meanwhile, other studies have shown that under the action of AS, the high-speed blood flow will be more concentrated, thus reducing the generation of surrounding vortices [54]. Campobasso et al. showed that rigid AsAA might have the most significant variation in wall stress distribution.
Ascending aortic aneurysm (AsAA) is a high-risk cardiovascular disease with an increased incidence over years. In this study, we compared different risk factors based on the pre-failure behavior (from a biomechanical point of view) obtained ex-vivo from an equi-biaxial tensile test.
A total of 100 patients (63 ± 12 years, 72 males) with AsAA replacement, were recruited. Equi-biaxial tensile tests of AsAA walls were performed on freshly sampled aortic wall tissue after ascending aortic replacement. The aneurysmal aortic walls were divided into four quadrants (medial, anterior, lateral, and posterior) and two directions (longitudinal and circumferential) were considered. The stiffness was represented by the maximum Young modulus (MYM). Based on patient information, the following subgroups were considered: age, gender, hypertension, obesity, dyslipidemia, diabetes, smoking history, aortic insufficiency, aortic stenosis, coronary artery disease, aortic diameter and aortic valve type.
In general, when the aortic diameter increased, the aortic wall became thicker. In terms of the MYM, the longitudinal direction was significantly higher than that in the circumferential direction. In the multivariant analysis, the impact factors of age (p = 0.07), smoking (p = 0.05), diabetes (p = 0.03), aortic stenosis (p = 0.02), coronary artery disease (p < 10⁻³), and aortic diameters (p = 0.02) were significantly influencing the MYM. There was no significant MYM difference when the patients presented arterial hypertension, dyslipidemia, obesity, or bicuspid aortic valve. To conclude, the pre-failure aortic stiffness is multi-factorial, according to our population of 100 patients with AsAA.
Our research on the topic of “Aortic local biomechanical properties in case of ascending aortic aneurysms” is about the biomechanical properties on one hundred aortic samples according to the aortic wall quadrants and the direction. More than ten factors and risks which may impact ascending aortic aneurysms have been studied. According to our knowledge, so far, this article involved the largest population on this topic. It will be our pleasure to share this information with all the readers.
Application of multiscale coupling models in the numerical study of circulation system
2022, Medicine in Novel Technology and Devices
Citation Excerpt :
Quarteroni et al. pointed out that it is reasonable to use explicit solvers or semi-implicit solvers in 3D-0D coupling problems with a simple structure, but using implicit coupling methods in more complex coupling problems can improve the stability of the solution. In the solution of the 3D-0D coupling model by Cosentino et al., the solver based on the implicit method was used in the coupling between a LP heart model and a personalized 3D finite element model of the aorta [49]; Ceballos et al. used the 3D-0D model to study the effect of the reverse Blalock-Taussing shunt on the local and overall flow dynamics. The coupling model was solved using the same implicit coupling approach [50].
Cardiovascular diseases have become a serious threat to human health now. With the rapid development of computer technology and medical imaging technology, the method of numerical simulation has become the main tool to explore the mechanism of cardiovascular diseases and to optimize the treatment planning. The cardiovascular system is a complex vascular network with multiscale characteristics, and the local hemodynamic phenomena in blood vessels is closely related to the overall blood flow distribution of the system. The hemodynamic characteristics in the local vessel and circulation system influences each other. Therefore, the traditional single-scale modeling method cannot accurately describe the real blood flow in blood vessels. While the numerical simulation of multiscale coupling model can effectively solve this problem. In this paper, the main methods of hemodynamic modeling in recent years are summarized, including lumped parameter model (0D model), distributed parameter model (1D model) and finite element model of (3D model), and their applications in cardiovascular studies. On this basis, the principles of several commonly used multiscale coupling models and their applications in cardiovascular disease researches and clinical practice are introduced, including 1D-0D, 3D-0D, and 3D-1D coupling model.
Simulating impaired left ventricular–arterial coupling in aging and disease: a systematic review
2024, BioMedical Engineering Online
Evaluating Uncertainties in CFD Simulations of Patient-Specific Aorta Models using Grid Convergence Index Method
2023, arXiv

View all citing articles on Scopus

View full text

On the severity of aortic stenosis in ascending aortic aneurysm: A computational tool to examine ventricular-arterial interaction and aortic wall stress

Highlights

Abstract

Section snippets

1. Introduction

2.1. ATAA segmentation and meshing

3. Results

4. Discussion

5. Conclusion

Declaration of Competing Interest

Acknowledgment

J. Am. Coll. Cardiol.

Ann. Thorac. Surg.

J. Thorac. Cardiovasc. Surg.

Int. J. Cardiol.

Eur. J. Vasc. Endovasc. Surg.

Ann. Thorac. Surg.

Ann. Thorac. Surg.

Ann. Thorac. Surg.

Int. J. Cardiol.

Med. Eng. Phys.

J. Mol. Cell. Cardiol.

Int. J. Cardiol.

Acta Biomater.

Comput. Biol. Med.

Comput. Biol. Med.

Aortic dilatation in patients with bicuspid aortic valve

N. Engl. J. Med.

Bicuspid aortic valve: identifying knowledge gaps and rising to the challenge from the international bicuspid aortic valve consortium (BAVCon)

Circulation