Computational Fluid Dynamics and Aortic Thrombus Formation Following Thoracic Endovascular Aortic Repair

doi:10.1016/j.athoracsur.2016.09.067

The Annals of Thoracic Surgery

Volume 103, Issue 6, June 2017, Pages 1914-1921

https://doi.org/10.1016/j.athoracsur.2016.09.067 Get rights and content

Background

We present the possible utility of computational fluid dynamics in the assessment of thrombus formation and virtual surgical planning illustrated in a patient with aortic thrombus in a kinked ascending aortic graft following thoracic endovascular aortic repair.

Methods

A patient-specific three-dimensional model was built from computed tomography. Additionally, we modeled 3 virtual aortic interventions to assess their effect on thrombosis potential: (1) open surgical repair, (2) conformable endografting, and (3) single-branched endografting. Flow waveforms were extracted from echocardiography and used for the simulations. We used the computational index termed platelet activation potential (PLAP) representing accumulated shear rates of fluid particles within a fluid domain to assess thrombosis potential.

Results

The baseline model revealed high PLAP in the entire arch (119.8 ± 42.5), with significantly larger PLAP at the thrombus location (125.4 ± 41.2, p < 0.001). Surgical repair showed a 37% PLAP reduction at the thrombus location (78.6 ± 25.3, p < 0.001) and a 24% reduction in the arch (91.6 ± 28.9, p < 0.001). Single-branched endografting reduced PLAP in the thrombus region by 20% (99.7 ± 24.6, p < 0.001) and by 14% in the arch (103.8 ± 26.1, p < 0.001), whereas a more conformable endograft did not have a profound effect, resulting in a modest 4% PLAP increase (130.6 ± 43.7, p < 0.001) in the thrombus region relative to the baseline case.

Conclusions

Regions of high PLAP were associated with aortic thrombus. Aortic repair resolved pathologic flow patterns, reducing PLAP. Branched endografting also relieved complex flow patterns reducing PLAP. Computational fluid dynamics may assist in the prediction of aortic thrombus formation in hemodynamically complex cases and help guide repair strategies.

Section snippets

Clinical Data

CTA was performed with 64-slice scanners and intravenous injection of 80 to 120 mL of nonionic iodinated contrast material. The CTA was used to build the computational models. MRI studies were conducted using a gadolinium-based contrast agent (gadobenate dimeglumine) and steady-state free precession cine imaging. Additionally, black blood imaging and multiphase dynamic three-dimensional MRI were performed with the injection of the contrast bolus to visualize aortic thrombus. Approval was

Results

The computed hemodynamics of the baseline model are summarized in Figure 3. Peak flow was 304.7 mL/s and 254.2 mL/s in the ascending and denscending aorta, respectively. Retrograde diastolic flow was observed in both ascending (with a peak of 0.2 mL/s) and descending aorta (peak of 25.8 mL/s). The different flow and pressure waveforms show realistic profiles for all branches of the model, including predominantly diastolic flow in the left coronary artery, matched mean values of pressure and

Comment

This study demonstrated a correlation between intraluminal ascending aortic thrombus and high levels of intraluminar shear through CFD analysis. Complex flow patterns in a complex geometry resulting from kinking of a vascular graft appear to significantly contribute to the increase in shear rates between blood particles. Such shear is known to activate platelets with altered risk of thrombus formation 6, 7. This study had two primary motivations: (1) to confirm the suitability of the platelet

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Thoracic Stent Graft Numerical Models To Virtually Simulate Thoracic Endovascular Aortic Repair: A Scoping Review
2023, European Journal of Vascular and Endovascular Surgery
Pre-procedural planning of thoracic endovascular aortic repair (TEVAR) may implement computational adjuncts to predict technical and clinical outcomes. The aim of this scoping review was to explore the currently available TEVAR procedure and stent graft modelling options.
PubMed (MEDLINE), Scopus, and Web of Science were systematically searched (English language, up to 9 December 2022) for studies presenting a virtual thoracic stent graft model or TEVAR simulation.
The Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) was followed. Qualitative and quantitative data were extracted, compared, grouped, and described. Quality assessment was performed using a 16 item rating rubric.
Fourteen studies were included. Among the currently available in silico simulations of TEVAR, severe heterogeneity exists in study characteristics, methodological details, and evaluated outcomes. Ten studies (71.4%) were published during the last five years. Eleven studies (78.6%) included heterogeneous clinical data to reconstruct patient specific aortic anatomy and disease (e.g., type B aortic dissection, thoracic aortic aneurysm) from computed tomography angiography imaging. Three studies (21.4%) constructed idealised aortic models with literature input. The applied numerical methods consisted of computational fluid dynamics analysing aortic haemodynamics in three studies (21.4%) and finite element analysis analysing structural mechanics in the others (78.6%), including or excluding aortic wall mechanical properties. The thoracic stent graft was modelled as two separate components (e.g., graft, nitinol) in 10 studies (71.4%), as a one component homogenised approximation (n = 3, 21.4%), or including nitinol rings only (n = 1, 7.1%). Other simulation components included the catheter for virtual TEVAR deployment and numerous outcomes (e.g., Von Mises stresses, stent graft apposition, drag forces) were evaluated.
This scoping review identified 14 severely heterogeneous TEVAR simulation models, mostly of intermediate quality. The review concludes there is a need for continuous collaborative efforts to improve the homogeneity, credibility, and reliability of TEVAR simulations.
One year follow-up outcomes of endovascular treatment for aortic dissection with a partial micropore stent graft in which fixation of the stent is done in zone 0: A pivotal trial first in human
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This study aimed to verify the efficacy and safety of the treatment for patients diagnosed with DeBakey type I and type III thoracic aortic dissections using a partial micropore stent graft.
We conducted a retrospective analysis of 32 patients who suffered from thoracic aortic dissection and underwent endovascular repair using a partial micropore stent graft at our center between December 2018 and January 2020.
The technical success rate for 32 patients was 100 %, while no 30-day mortality was observed. In the 30 patients finished follow-ups, 30 (mean: 1 per patient) micropore stents were implanted, while the openings of 90 (mean: 3 per patient) aortic arch branches were covered by the stents. After more than 12 months follow-up, 26 (86.7 %) of the 30 patients presented with a complete thrombosis in the false lumen, and 4 (13.3 %) patients presented with a partial thrombosis in the false lumen. All 90 aortic arch branches were patent. No aortic arch branch artery stenosis or occlusion was observed.
The outcomes obtained during 12 months of follow-up suggested that performing endovascular repair for thoracic aortic dissection patients with a partial micropore stent graft is safe and effective, maintaining the patency of aortic arch branch vessels.
Near-wall hemodynamic changes in subclavian artery perfusion induced by retrograde inner branched thoracic endograft implantation
2023, JVS-Vascular Science
Left subclavian artery (LSA)-branched endografts with retrograde inner branch configuration (thoracic branch endoprosthesis [TBE]) offer a complete endovascular solution when LSA preservation is required during zone 2 thoracic endovascular aortic repair. However, the hemodynamic consequences of the TBE have not been well-investigated. We compared near-wall hemodynamic parameters before and after the TBE implantation using computational fluid dynamic simulations.
Eleven patients who had undergone TBE implantation were included. Three-dimensional aortic arch geometries were constructed from the pre- and post-TBE implantation computed tomography images. The resulting 22 three-dimensional aortic arch geometries were then discretized into finite element meshes for computational fluid dynamic simulations. Inflow boundary conditions were prescribed using normal physiological pulsatile circulation. Outlet boundary conditions consisted of Windkessel models with previously published values. Blood flow, modeled as Newtonian fluid, simulations were performed with rigid wall assumptions using SimVascular's incompressible Navier-Stokes solver. We compared well-established hemodynamic descriptors: pressure, flow rate, time-averaged wall shear stress (TAWSS), the oscillatory shear index (OSI), and percent area with an OSI of >0.2. Data were presented on the stented portion of the LSA.
TBE implantation was associated with a small decrease in peak LSA pressure (153 mm Hg; interquartile range [IQR], 151-154 mm Hg vs 159 mm Hg; IQR, 158-160 mm Hg; P = .005). No difference was observed in peak LSA flow rates before and after implantation: 40.4 cm³/ (IQR, 39.5-41.6 cm³/s) vs 41.3 cm³/s (IQR, 37.2-44.8 cm³/s; P = .59). There was a significant postimplantation increase in TAWSS (15.2 dynes/cm² [IQR, 12.2-17.7 dynes/cm²] vs 6.2 dynes/cm² [IQR, 5.7-10.3 dynes/cm²]; P = .003), leading to decreases in both the OSI (0.088 [IQR, 0.063 to –0.099] vs 0.1 [IQR, 0.096-0.16]; P = .03) and percentage of area with an OSI of >0.2 (10.4 [IQR, 5.8-15.8] vs 15.7 [IQR, 10.7-31.9]; P = .13). Neither LSA side branch angulation (median, 81°, IQR, 77°-109°) nor moderate compression (16%-58%) seemed to have an impact on the pressure, flow rate, TAWSS, or percentage of area with an OSI of >0.2 in the stented LSA.
The implantation of TBE produces modest hemodynamic disturbances that are unlikely to result in clinically relevant changes.
Patient-specific computational fluid dynamics of femoro-popliteal stent-graft thrombosis
2020, Medical Engineering and Physics
Citation Excerpt :
Artificial surfaces, such as the inner layer of stent-graft, promote clotting through a complex series of interconnected processes, from protein adsorption to adhesion of platelets, through thrombin generation and complement activation [35]. Further developments of the present study should consider the role of hemodynamic stress in the platelet activation [36], recently proved to be predictive of aortic thrombus formation following thoracic endovascular aortic repair [37]. Finally, stent struts are not taken into consideration in the present study; however, the stent struts have an effect on wall shear stress [38], further developments will target this aspect.
Intra-stent thrombosis is one of the major failure modes of popliteal aneurysm endovascular repair, especially when the diseased arterial segment is long and requires overlapping stent-grafts having different nominal diameters in order to accommodate the native arterial tapering.
However, the interplay between stent sizing, post-operative arterial tortuosity, luminal diameter, local hemodynamics, and thrombosis onset is not elucidated, yet.
In the present study, a popliteal aneurysm was treated with endovascular deployment of two overlapped stent-grafts, showing intra-stent thrombosis at one-year follow-up examination. Patient-specific computational fluid-dynamics analyses including straight- and bent-leg position were performed.
The computational fluid-dynamics analysis showed that the overlapping of the stent-grafts induces a severe discontinuity of lumen, dividing the stented artery in two regions: the proximal part, affected by thrombosis, is characterized by larger diameter, low tortuosity, low flow velocity, low helicity, and low wall shear stress; the distal part presents higher tortuosity and smaller lumen diameter promoting higher flow velocity, higher helicity, and higher wall shear stress. Moreover, leg bending induces an overall increase of arterial tortuosity and reduces flow velocity promoting furtherly the luminal area exposed to low wall shear stress.
Computational Fluid Dynamics Modeling of Hemodynamic Parameters in the Human Diseased Aorta: A Systematic Review
2020, Annals of Vascular Surgery
The analysis of the correlation between blood flow and aortic pathology through computational fluid dynamics (CFD) shows promise in predicting disease progression, the effect of operative intervention, and guiding patient treatment. However, to date, there has not been a comprehensive systematic review of the published literature describing CFD in aortic diseases and their treatment.
This review includes 136 published articles which have investigated the application of CFD in all types of aortic disease (aneurysms, dissections, and coarctation). We took into account case studies of both, treated or untreated pathology, investigated with CFD. We also graded all studies using an author-defined Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach based on the validation method used for the CFD results.
There are no randomized controlled trials assessing the efficacy of CFD as applied to aortic pathology, treated or untreated. Although a large number of observational studies are available, those using clinical imaging tools as independent validation of the calculated CFD results exist in far smaller numbers. Only 21% of all studies used clinical imaging as a tool to validate the CFD results and these were graded as high-quality studies.
Contemporary evidence shows that CFD can provide additional hemodynamic parameters such as wall shear stress, vorticity, disturbed laminar flow, and recirculation regions in untreated and treated aortic disease. These have the potential to predict the progression of aortic disease, the effect of operative intervention, and ultimately help guide the choice and timing of treatment to the benefit of patients and clinicians alike.
Hemodynamic Analysis to Assist Treatment Strategies in Complex Visceral Arterial Pathologies: Case Reports and discussion from Pancreaticoduodenal Artery Aneurysm with Superior Mesenteric Artery Occlusion
2019, Annals of Vascular Surgery
Citation Excerpt :
In this study, use of CFD offers new insights into the preoperative and postoperative hemodynamic changes in PDAA with SMA and IMA occlusion. Also, it demonstrated that utilization of CFD analysis may possibly help surgeons in operation planning.27–29 More studies will be needed for the feasibility and effectivity of CFD simulation assisting operation strategy in the near future.
Pancreaticoduodenal artery aneurysms (PDAAs) with occlusion of the superior mesenteric artery (SMA) are extremely rare. In the present study, we used computational fluid dynamics (CFD) to analyze the hemodynamics of a patient-specific PDAA with occlusion of the SMA preoperatively and then decide the treatment strategy in terms of the potential postoperative hemodynamics.
A 3D model of a 69-old-year female with PDAA was reconstructed based on CT images. The virtual postoperative models of the aneurysmectomy with or without revascularization were numerically simulated in terms of hemodynamics including the flow field and wall shear stress (WSS).
Aneurysmectomy with revascularization would result in the original aneurysm site experiencing abnormally high WSS and pressure, which may possibly lead to the recurrence of PDAA. However, aneurysmectomy without revascularization would lead to stagnant flow in the blocked posterior-inferior pancreaticoduodenal artery (PIPDA). As a result, the PIPDA may soon be completely occluded after surgery and the SMA perfusion would be guaranteed. Finally, aneurysmectomy without revascularization was performed in this patient. The postoperative six-month computed tomography angiography result finely matched to the preoperative CFD simulation result.
This study gained insights into hemodynamics of PDAA. In addition, it demonstrated that utilization of CFD analysis also possibly helps assist the operation strategies for vascular diseases.

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Original articleAdult cardiacComputational Fluid Dynamics and Aortic Thrombus Formation Following Thoracic Endovascular Aortic Repair

Background

Methods

Results

Conclusions

Section snippets

Clinical Data

Results

Comment

J Thorac Cardiovasc Surg

J Vasc Surg

J Thorac Cardiovasc Surg

J Vasc Surg

Blood

Eur J Vasc Endovasc Surg

J Vasc Surg

Retrograde aortic dissection after thoracic endovascular aortic repair

Ann Surg

A computational framework for investigating the positional stability of aortic endografts

Biomech Model Mechanobiol

A haemodynamic predictor of intraluminal thrombus formation in abdominal aortic aneurysms

Proc R Soc A Math Phys Eng Sci

Original article
Adult cardiac
Computational Fluid Dynamics and Aortic Thrombus Formation Following Thoracic Endovascular Aortic Repair