Analysis of Aortic Arch Hemodynamics With Simulated Bird's Beak Effects

OBJECTIVE

The objective of this study was to investigate the flow effects in different degrees of thoracic aortic stent graft protrusion extension by creating bird beak effect simulations using accurate 3D geometry and a realistic, nonlinear, elastic biomechanical model using computer-aided software SolidWorks.

METHODS

Segmentation in 3D of an aortic arch from a computed tomography (CT) scan of a real-life patient was performed using SolidWorks. A parametric analysis of three models was performed: (A) Aortic arch with no stent, (B) 3 mm bird-beak configuration, and (C) 6.5 mm bird-beak configuration. Flow velocity, pressure, vorticity, wall shear stress (WSS), and time average WSS were assessed.

RESULTS

The flow velocity in Model A remained relatively constant and low in the area of the ostium of the brachiocephalic artery and doubled in the left subclavian artery. On the contrary, Models B and C showed a decrease in velocity of 52.3 % in the left subclavian artery. Furthermore, Model B showed a drop in velocity of 82.7% below the bird-beak area, whereas Model C showed a decline of 80.9% in this area. The pressure inside the supra-aortic branches was higher in Model B and C compared with Model A. In Model A, vorticity only appeared at the level of the descending aorta, with low to non-vorticity in the aortic arch. In contrast, Models B and C had an average vorticity of 241.4 Hz within the bird beak area. Regarding WSS, Model A, and Model B shared similar WSS in the peak systolic phase, in the aortic arch, and the bird beak area, whereas Model C had an increased WSS by 5 Pa on average at these zones.

CONCLUSION

In the present simulations' lower velocities, higher pressures, vortices, and WSS were observed around the bird beak zone, the aortic arch, and the supra-aortic vessels.

A computational study of artery curvature and endograft oversize influence on seal zone behavior in endovascular aortic repair

Thoracic endovascular aortic repair (TEVAR) is a minimally invasive procedure involving the placement of an endograft inside the dissection or an aneurysm to direct blood flow and prevent rupture. A significant challenge in endovascular surgery is the geometrical mismatch between the endograft and the artery, which can lead to endoleak formation, a condition where blood leaks between the endograft and the vessel wall. This study uses computational modeling to investigate the effects of artery curvature and endograft oversizing, the selection of an endograft with a larger diameter than the artery, on endoleak creation. Finite element analysis is employed to simulate the deployment of endografts in arteries with varying curvature and diameter. Numerical simulations are conducted to assess the seal zone and to quantify the potential endoleak volume as a function of curvature and oversizing. A theoretical framework is developed to explain the mechanisms of endoleak formation along with proof-of-concept experiments. Two main mechanisms of endoleak creation are identified: local buckling due to diameter mismatch and global buckling due to centerline curvature mismatch. Local buckling, characterized by excess graft material buckling and wrinkle formation, increases with higher levels of oversizing, leading to a larger potential endoleak volume. Global buckling, where the endograft bends or deforms to conform to the centerline curvature of the artery, is observed to require a certain degree of oversizing to bridge the curvature mismatch. This study highlights the importance of considering both curvature and diameter mismatch in the design and clinical use of endografts. Understanding the mechanisms of endoleak formation can provide valuable insights for optimizing endograft design and surgical planning, leading to improved clinical outcomes in endovascular aortic procedures.

Incidence, Predictors, and Implications of Secondary Aortic Intervention Following Thoracic Endovascular Aortic Repair for Type B Dissection

BACKGROUND

Secondary aortic intervention (SAI) following thoracic endovascular aortic repair (TEVAR) is not uncommon. However, a satisfactory management system has not been established for these patients. We aimed to report our single-center experience with SAI after prior TEVAR for type B aortic dissection (TBAD).

METHODS

From January 2010 to May 2017, 860 eligible patients with TBAD underwent TEVAR. One hundred seven (12.4%) patients required SAI, either endovascularly (n=76) or surgically (n=31). The main indications for SAI were entry flow (n=58 [54.2%]), aneurysm expansion of the proximal or remote aorta (n=26 [24.3%]), retrograde type A aortic dissection (n=11 [10.3%]), distal stent-graft-induced new entry tear (n=6 [5.6%]), and stent migration (n=4 [3.7%]). The Kaplan-Meier curves were generated to determine the degree of freedom from SAI and the prognosis. Cox proportional hazards were used to screen for risk factors for SAI and poor prognosis.

RESULTS

The overall 30-day mortality rate after SAI was 4.7% (n=5): endovascular (n=2 [2.6%]) vs open surgery (n=3 [9.7%]; p=0.145). The cumulative survival rates with or without SAI were 86.3%±3.6% vs 95.7%±0.8% at 3 years and 82.0%±4.2% vs 92.2%±1.1% at 5 years, respectively (log-rank p<0.001). Although no significant difference in survival was observed, the incidence of SAI was significantly greater in patients who underwent TEVAR during the chronic phase (acute [11.6%] vs subacute [9.6%] vs chronic [27.8]; p<0.001). Multivariate regression analysis revealed that prior TEVAR in the chronic phase (hazard ratio [HR]=1.73, 95% confidence interval [CI]=1.03-2.90; p=0.039), maximum aortic diameter (HR=1.05, 95% CI=1.04-1.07; p<0.001), and arch involvement (HR=1.48, 95% CI=1.01-2.18; p=0.048) were predictors of the incidence of SAI. In addition, the maximum aortic diameter was demonstrated to be the only risk factor for prognosis after adjusting for confounding factors.

CONCLUSIONS

Thoracic endovascular aortic repair for chronic TBAD patients should be reconsidered. Open surgery is preferable for those with proximal progression, whereas endovascular treatment is more suitable for distal lesions. Close surveillance and timely reintervention after TEVAR, whether via endovascular techniques or open surgery, are necessary to prevent devastating complications.

CLINICAL IMPACT

The management of patients with type B aortic dissection (TBAD) after thoracic endovascular aortic repair (TEVAR) is challenging. We summarized our single-center experience regarding secondary aortic intervention after TEVAR for TBAD. We found that TEVAR for chronic TBAD patients should be carefully evaulated, and open surgery is recommended for those with proximal progession, while endovascular treatment is more preferable for distal lesions.

Long-term outcomes of thoracic endovascular aortic repair for the treatment of descending thoracic aortic aneurysms: a systematic review and meta-analysis

INTRODUCTION

We undertook a systematic review of the currently published literature on TEVAR for DTAAs and we combined the eligible studies into a meta-analysis with the intention of evaluating the efficacy and the long-term durability of this treatment option.

EVIDENCE ACQUISITION

A systematic search of the literature from January 2015 up to December 2022 was performed according to the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines. For events during follow-up we calculated the incidence rates (IRs) with 95% confidence intervals (95% CIs) per 100 patient-years (p-ys) as the number of patients with outcome events occurring during the specific time period divided by the total number of p-ys.

EVIDENCE SYNTHESIS

A total of 4127 study titles were identified by the initial search strategy, of which 12 were considered eligible for inclusion in the meta-analysis. A Total of 1976 patients (62% male) were identified among the eligible studies. One-year survival was 90.1% (95% CI 86.3% to 93.0%), 3-year survival was estimated at 80.5% (95% CI 69.2% to 88.4%) and the 5-year survival was estimated at 73.2% (95%CI 64.3% to 80.5%) with significant heterogeneity among studies regarding these outcomes. Regarding freedom from reintervention analysis for 1 year and 5 years was 96.5% (95% CI 94.5% to 97.8%) and 85.4% (95% CI 56.7% to 96.3%) respectively. The pooled late complications IR per 100 p-ys was 55.0 (95% CI 39.1 to 70.9), whereas the pooled IR for late reinterventions per 100 p-ys was 21.2 (95% CI 26.0 to 87.5). Late type I endoleak was reported with a pooled IR of 26.7 per 100 p-ys (95% CI 19.8 to 33.6) and late type III endoleak with a pooled IR of 7.6 per 100 p-ys (95% CI 5.5 to 9.7).

CONCLUSIONS

TEVAR presents a safe and feasible solution for the treatment of DTAA with sustained long-term effectivity. Current evidence supports a satisfactory 5-year survival with low rates of reinterventions.

Thoracic endovascular repair for blunt traumatic thoracic aortic injury: Long-term results

OBJECTIVE

This study aims to evaluate the endoprosthesis complications in patients undergoing TEVAR for blunt traumatic thoracic aortic injury, through long-term clinical and diagnostic follow-up.

METHODS

During the study interval (November 2000-October 2020), a total of 38 patients (63% male; average age 37.5 years) with thoracic aortic injury underwent thoracic endovascular aortic repair. Patients underwent routine follow-up with clinical examination and radiological evaluation (CT-angiography or MRI-angiography plus chest radiograph), scheduled at 1 month, at 6 months (only in the cases of thoracic aortic dissection), at 1 year after the procedure and every 1 year thereafter.

RESULTS

Technical success was achieved in 38 procedures (100%). The TEVAR-related mortality rate was 0%. No immediate major complications related to the endovascular procedure were observed. The median duration of diagnostic follow-up was 80 months. A total of four procedure-related complications (10.5%) were identified at the follow-up. Three (7.9%) distal infoldings and collapses of the thoracic endoprosthesis and one (2.6%) type Ia endoleak were observed. No thrombosis of the prosthesis, nor signs of aortic pseudocoarctation were identified. No further complications related to endograft (endoleaks, infections, rupture, partial or complete thrombosis) occurred. No changes in the native aorta, stenosis, or increases in the endograft's diameters were observed. A total of 20 patients (52.6%) underwent MRI-angiography examinations, while a total of 34 patients (89.5%) underwent chest radiographs at the follow-up. In all cases, CT-angiography examinations were performed at the follow-up.

CONCLUSIONS

Procedure-related complications were observed within one year of TEVAR, limiting concerns related to the durability of the prosthesis. No morphological changes in the aorta were observed despite long-term follow-up. The consequences of lifelong surveillance in terms of radiation exposure deserve special consideration, especially in younger patients treated for TAI.

Intramural hematoma in the proximal sealing zone of the thoracic endovascular aneurysm repair: frequency and safety in acute and subacute type B dissections

Introduction

To assess the outcomes after thoracic endovascular aneurysm repair (TEVAR) in the presence of intramural hematoma (IMH) in the proximal sealing zone.

Material and methods

Patient data were retrospectively extracted from the hospital records of patients treated with TEVAR for acute and chronic aortic dissection type B in one single center. The initial, preoperative, first postoperative, and last follow-up CT scans were evaluated in the aortic 3D multiplanar reformats and the centerline regarding IMH presence in the proximal sealing zone, anatomical preconditions, and the morphological TEVAR complications including migration and bird-beak. Groups with (IMH) and without IMH (no-IMH) were compared.

Results

Overall, 84 patients (IMH:42; no-IMH:42) were treated at the age of 63(55; 72) years, of whom 23/84 (27%), 34/84 (40%), and 27/84 (32%) were in the hyperacute, acute and subacute dissection phases, respectively. The bovine arch was found in 10/84(12%) and the type III arch was most common (43/84;51%). IMH maximum extent was found in zones 0, 1, 2, and 3 in 14/84 (17%), 17/84 (20%), 18/84 (21%), and 6/84 (7%), respectively. Sealing was achieved in zone II in 71/84 (85%) and LSA was revascularized in 66/84 (79%) of the overall cohort. Early mortality and paraplegia were 2/84 (2%) each; stroke rate was 3/84 (4%). During the 22 months median follow-up (22;4;43) no RTAD was observed. Migration ≥10 mm (IMH: 11/82; no-IMH: 10/82; P = 1.0) and bird-beaks (IMH: 10/82; no-IMH: 12/82; P = 0.8036) were comparable in both groups and accompanied by a low aorta related mortality (1/82) in both groups.

Conclusion

The presence of the IMH in the proximal TEVAR sealing zone is frequent and may not be relevant for the occurrence of the RTAD, stent-graft migration, or bird-beak formation.

Prediction of bird-beak configuration in thoracic endovascular aortic repair preoperatively using patient-specific finite element simulations

Objectives

Formation of bird-beak configuration in thoracic endovascular aortic repair (TEVAR) has been shown to be correlated with the risk of complications such as type Ia endoleaks, stent graft migration, and collapse. The aim of this study was to use patient-specific computational simulations of TEVAR to predict the formation of bird-beak configuration preoperatively.

Methods

Patient-specific TEVAR computational simulations are developed using a retrospective cohort of patients treated for thoracic aortic aneurysm. The preoperative computed tomography images were segmented to develop three-dimensional geometry of the thoracic aorta. These geometries were used in finite element simulations of stent graft deployment during TEVAR. Simulated results were compared against the postoperative computed tomography images to assess the accuracy of simulations in predicting the proximal position of a deployed stent graft and presence of bird-beak. In cases with a bird-beak configuration, the length and angle of the bird-beak were measured and compared between the simulated and postoperative results.

Results

Twelve TEVAR patient cases were simulated. Computational simulations were able to accurately predict whether the proximal stent graft was fully apposed, proximal bare stents were protruded, or bird-beak configuration was present. In three cases with bird-beak configuration, simulations predicted the length and angle of the bird-beak with less than 10% and 24% error, respectively. Other factors such as a small aortic arch angle, small oversizing value, and landing zones close to the arch apex may have played a role in formation of bird-beak in these patients.

Conclusions

Computational simulations of TEVAR accurately predicted the proximal position of a deployed stent graft and the presence of bird-beak preoperatively. The computational models were able to predict the length and angle of bird-beak configurations with good accuracy. These simulations can provide insight into the surgical planning process with the goal of minimizing bird-beak occurrence.

Blunt Thoracic Aortic Injury

Blunt thoracic aortic injury (BTAI) is a potentially fatal condition that needs prompt recognition and expedited management. Clinical manifestations of BTAI are not straight forwarding and may be misdiagnosed. The grade of aortic injury is an important determinant of perioperative mortality and morbidity, as well as the indication of treatment, along with the presence of concomitant lesions of other involved organs. The mainstay of treatment nowadays for hemodynamically stable patients who survive the trauma scene is represented by delayed endovascular repair whenever anatomically and clinically feasible. Endovascular repair, in fact, is burdened by lower perioperative mortality and morbidity rates if compared to open surgical repair, but concerns remain about the need for long-term surveillance and radiation exposure in patients who are at a younger age than patients treated for the aneurysmal disease. The aim of the paper is to provide an update on the diagnostic modalities and strategies of treatment for patients affected by BTAI.

Severe Tortuosity of the Distal Descending Thoracic Aorta Affects the Accuracy of Distal Deployment During a Thoracic Endovascular Aortic Repair

PURPOSE

An accurate distal deployment is essential for successful thoracic endovascular aortic repair (TEVAR) of a paradiaphragmatic aortic aneurysm. This study aimed to investigate the anatomical and intraoperative factors that affect the accuracy of distal deployment during TEVAR.

METHODS

We conducted a retrospective review of preoperative and postoperative computed tomography scans of 426 patients undergoing TEVAR at our institution between October 2008 and May 2021, of which the stent-graft was attempted to be deployed just above the celiac axis or the superior mesenteric artery in 56 patients. Based on the anatomical factors related to the malposition (deployed >10 mm away from the target vessel) and the greater curve to the straight-line ratio (G/S ratio), the patients were categorized as severe tortuosity (n=21) and mild tortuosity (n=35) groups to compare the operative and clinical outcomes.

RESULT

Stent-graft malpositioning occurred in 21 cases. Among all anatomical variables, only the G/S ratio was significantly larger in the malpositioned cases (p=0.049). A cutoff G/S ratio value of 1.15 was determined using the receiver operating curve analysis. In the severe tortuosity group, the distal end of the stent-graft was significantly farther (median: 10.0 [interquartile range (IQR): 2.5-19.5] mm vs 3.0 [0-8.0] mm; p=0.015) from the target vessel, and the tilt angle of the stent-graft's distal edge was larger (median: 21.4 [IQR: 15.8-24.5] vs 9.5 [5.5-12.5] degree; p<0.01) than that in the mild tortuosity group. Both groups were comparable for the incidence of a primary type Ib endoleak (p=0.454), a secondary type Ib endoleak (p=1.0), and the rate of distal reintervention (p=0.276).

CONCLUSION

Severe tortuosity in the distal descending thoracic aorta is associated with a malpositioned and tilted distal end of the stent-graft.

CLINICAL IMPACT

Thoracic endovascular aortic repair (TEVAR) for paradiaphragmatic thoracic aortic aneurysms requires accurate distal landing. In this paper, a retrospective CT analysis revealed that the greater curve to the straight-line ratio (G/S ratio) was associated to affects the malposition of the stent graft, defined as being deployed more than 10 mm away from the target vessel. Further, a comparative analysis based on the G/S ratio demonstrated that severe aortic tortuosity was associated with a more distal and tilted deployment of the stent graft.

Hybrid Approaches for Aortic Disease – Our Experience

BACKGROUND

Despite significant technological advancements in endovascular aortic repair, the aortic arch remains a challenge due to anatomic complexity including arch angulation and morphology as well as the location of brachiocephalic vessels in relation to landing zones. Total endovascular solutions are in development and being studied, in the meantime, hybrid thoracic endovascular aortic repair (TEVAR) is a viable alternative to traditional open total arch replacement.

METHODS

A retrospective case series was performed reviewing outcomes of 71 patients who underwent hybrid TEVAR in the aortic arch over the past 12 years at our facility.

RESULTS

Major morbidity in the first 30 days post procedure was experienced by 3 patients (15.7%) and included one patient with stroke (n = 1), and another who experienced paraplegia and pulmonary complications (n = 1). There was one in-hospital death as a result of respiratory failure in a patient with multiple underlying comorbidities including chronic obstructive pulmonary disease on postoperative day 5 resulting in a 30-day mortality of 5.2%. After a mean follow-up of 30 months, the overall mortality remained 5.2%. Major morbidity occurred in one patient who developed retrograde type A dissection. There was no stenosis of bypass grafts identified on follow-up imaging. Endoleak was identified in 2 patients. One patient experienced persistent retrograde perfusion of the false lumen with interval aneurysmal degeneration which was managed with an Amplatz vascular plug at 120 months following the initial hybrid TEVAR (5.2%).

CONCLUSIONS

Single-stage hybrid TEVAR in the aortic arch is technically feasible with a good mid-term survival and a long-term freedom from reintervention.

[Update on thoracic endovascular aneurysm repair : New stent graft designs]

BACKGROUND

In the last decade, new stent graft designs have evolved to tackle challenges in thoracic endovascular aortic repair. A specific focus on access vessel issues has led to the introduction of new low-profile endograft designs for most of the major products.

OBJECTIVE

The main objective of this article is to provide an overview of the available publications on new stent graft designs.

MATERIALS AND METHODS

Assessing recent publications on the major reiterations of thoracic endografts, benefits and drawbacks are discussed.

RESULTS

Recent reiterations of major endografts for thoracic aortic endovascular repair have focused mainly on the development of low-profile devices. Through alterations on graft fabric as well as stent material and design, delivery systems were reduced in profile, thus, reducing access vessel complications or enabling an endovascular procedure altogether. Long-term data are already available for one endoprosthesis. Other refinements include in situ adaptation of the stent graft to the aortic arch curvature as well as the option of staged deployment to allow more precision and reduce manipulation close to supra-aortic branches.

CONCLUSIONS

Especially in the case of low-profile endografts, preliminary and long-term results of access vessel complications are promising. In order to draw final conclusions as to how durable the results of aneurysm exclusion are, more long-term studies are warranted.

Validation and Verification of High-Fidelity Simulations of Thoracic Stent-Graft Implantation

Thoracic Endovascular Aortic Repair (TEVAR) is the preferred treatment option for thoracic aortic pathologies and consists of inserting a self-expandable stent-graft into the pathological region to restore the lumen. Computational models play a significant role in procedural planning and must be reliable. For this reason, in this work, high-fidelity Finite Element (FE) simulations are developed to model thoracic stent-grafts. Experimental crimp/release tests are performed to calibrate stent-grafts material parameters. Stent pre-stress is included in the stent-graft model. A new methodology for replicating device insertion and deployment with explicit FE simulations is proposed. To validate this simulation, the stent-graft is experimentally released into a 3D rigid aortic phantom with physiological anatomy and inspected in a computed tomography (CT) scan at different time points during deployment with an ad-hoc set-up. A verification analysis of the adopted modeling features compared to the literature is performed. With the proposed methodology the error with respect to the CT is on average 0.92 ± 0.64%, while it is higher when literature models are adopted (on average 4.77 ± 1.83%). The presented FE tool is versatile and customizable for different commercial devices and applicable to patient-specific analyses.

Large Diameter Advanta V12 Covered Stent Trial for Coarctation of the Aorta: COARC Study

BACKGROUND

Covered stent implantation for treatment of coarctation of the aorta (CoA) is effective and can prevent aortic wall injury. Prospective studies with long-term follow-up, including imaging, are lacking. We report the acute and long-term outcomes for use of the Large Diameter Advanta V12 covered stent for treatment of native and recurrent CoA.

METHODS

A prospective, multicenter, nonrandomized study was performed including 70 patients (43 male), median age 17 years, median weight 57.4 kg with CoA who underwent implantation of the Large Diameter Advanta V12 covered stent. Annual follow-up for 5 years included Doppler echocardiography to calculate diastolic velocity: systolic velocity ratio.

RESULTS

CoA diameter increased from 5.6±3.6 to 14.9±3.9 mm (P<0.0001) and the pressure gradient decreased from 35.8±16.2 to 5.6±7.9 mm Hg (P<0.0001). Preimplantation diastolic velocity:systolic velocity of 0.6±0.16 dropped to 0.34±0.13 (P<0.0001) and was maintained at 5 years. Computed tomography angiograms at 12 months postimplantation demonstrated the stent:transverse arch diameter to be similar, 0.91±0.09 to postprocedure 0.86±0.14. Major adverse vascular events at 30 days and 12 months were 1.4% and 4.3%, respectively. Significant adverse events included three patients who required stent implantation to treat infolding. There were no mortalities.

CONCLUSIONS

The Large Diameter Advanta V12 covered stent is safe and effective for the treatment of CoA with an immediate and sustained reduction of the pressure gradient over 12 months and 5 years as assessed by preimplantation and postimplantation Doppler echocardiography and 12-month computed tomography angiography.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT00978952. URL: http://www.anzctr.org.au; Unique identifier: ACTRN12612000013864.

Association between aortic arch angulation and bird-beak configuration after thoracic aortic stent graft repair of type B aortic dissection

OBJECTIVES

The goal of this study was to investigate factors favouring the bird-beak configuration after thoracic endovascular aortic repair (TEVAR) for type B aortic dissection.

METHODS

We retrospectively analysed 76 patients with type B aortic dissection who underwent landing zone 1 and 2 TEVAR from December 2015 to January 2018. Preoperative aortic arch geometry (aortic arch length, maximal diameter and angulation), stent graft details and operative details were evaluated. A bird-beak configuration was defined as a ≥5-mm gap between the proximal end of the stent and the aortic wall of the lesser curvature.

RESULTS

Patients were stratified into those with (n = 46) and without (n = 30) a bird-beak configuration. The baseline demographics, dissection chronicity, clinical features and implanted devices were largely similar between the 2 groups. No significant difference was observed in the arch length or maximal arch diameter. However, the mean aortic arch angulation was greater in patients with than without a bird-beak configuration (61.4° vs 51.3°; P < 0.001). No influence of either the stent graft brand or the proximal stent graft type was observed. The multivariable analysis showed that the aortic arch angulation was an independent risk factor for a bird-beak configuration (odds ratio 1.15, 95% confidence interval 1.07-1.24; P < 0.001). A cut-off angle of 59.15° was predictive of a bird-beak configuration (sensitivity 59%; specificity 77%).

CONCLUSIONS

The preoperative aortic arch angulation was an independent predictor of a postoperative bird-beak configuration in patients with type B aortic dissection who underwent TEVAR that involved the aortic arch. An angle of >59.15° may imply a relatively hostile anatomy with a higher risk of a bird-beak configuration.

Impact of Thoracic Endografting on the Hemodynamics of the Native Aorta: Pre- and Postoperative Assessments of Wall Shear Stress and Vorticity Using Computational Fluid Dynamics

PURPOSE

To quantify the hemodynamic consequences of thoracic endovascular aortic repair (TEVAR) by comparing the preoperative and postoperative wall shear stress (WSS) and vorticity profiles on computational fluid dynamics (CFD) simulations.

MATERIALS AND METHODS

The pre- and postoperative computed tomography (CT) scans from 20 consecutive patients (median age 69 years, range 20-87) treated for different thoracic aortic pathologies (11 aneurysms, 5 false aneurysms, 3 penetrating ulcers, and 1 traumatic aortic rupture) were segmented to construct patient-specific CFD models using a meshless code. The simulations were run over the cardiac cycle, and the WSS and vorticity values measured at the proximal and distal landing zones were compared.

RESULTS

The CFD runs provided 4-dimensional simulations of blood flow in all patients. WSS and vorticity profiles at the proximal landing zone (located in zones 0-3 in 15 patients) varied in 18 and 20 of the cases, respectively; WSS was increased in 11 cases and the vorticity in 9. Pre- and postoperative WSS median values were 4.19 and 4.90 Pa, respectively. Vorticity median values were 40.38 and 39.17 Hz, respectively.

CONCLUSION

TEVAR induces functional alterations in the native thoracic aorta, though the prognostic significance of these changes is still unknown. CFD appears to be a valuable tool to explore aortic hemodynamics, and its application in a larger series would help define a predictive role for these hemodynamic assessments.

Computational Fluid Dynamics Modeling of Proximal Landing Zones for Thoracic Endovascular Aortic Repair in the Bovine Arch Variant

BACKGROUND

To assess the endograft displacement forces (DF), which quantify the forces exerted by the pulsatile blood flow on the vessel wall and transmitted on the terminal fixation site of the endograft after its deployment in proximal landing zones (PLZs) of the bovine aortic arch variant.

METHODS

Thirty healthy aortic computed tomographic angiographies of subjects with bovine arch configuration (10 per type of arch, I-III) were selected for the purpose of the study. A 3-dimensional model of the aortic arch lumen was reconstructed. Computational fluid dynamics modeling was then used to compute DF magnitude and orientation (i.e., x, y, and z axes) in PLZs of each case. DF values were normalized to the corresponding aortic wall area to estimate equivalent surface traction (EST).

RESULTS

DF were highest in zone 0, consistently with the greater surface area. DF in zone 3 were much greater than in zone 2 because of a 3-fold greater upward component (z axis) (P < 0.001), being therefore mainly oriented orthogonally to the aortic blood flow and to the vessel longitudinal axis in that zone. EST progressively increased from zone 0 toward more distal PLZs, with EST in zone 3 being much greater than that in zone 2 (P < 0.001). The same pattern was observed after stratification by type of arch.

CONCLUSIONS

The bovine arch is associated with a consistent fluid dynamic pattern, which identifies in zone 3 an unfavorable biomechanical environment for endograft deployment.

One-Year Results From the SURPASS Observational Registry of the CTAG Stent-Graft With the Active Control System

Purpose: To report the outcomes from the observational SURPASS registry, which was created to assess the performance of the Conformable TAG (CTAG) stent-graft with the Active Control System (ACS) in patients undergoing thoracic endovascular aortic repair (TEVAR) in a real-world setting. Materials and Methods: The SURPASS registry (ClinicalTrials.gov; identifier NCT03286400) was an observational, prospective, single-arm, post-market, international study that enrolled patients undergoing TEVAR using the CTAG with ACS for both acute and chronic thoracic aortic disease between October 2017 and July 2018. The CTAG with ACS features 2-stage deployment of the stent-graft and an optional angulation mechanism that modifies only the proximal end of the stent-graft. During the observation period, 127 patients (mean age 67.1±12.1 years, range 27–86; 92 men) were enrolled and treated for an array of aortic pathologies, including chronic and acute lesions and 4 ruptured descending thoracic aneurysms. The primary outcome of this study was technical success; secondary outcomes were clinical success and major adverse events at 30 days and 12 months. The numbers of 2-stage device deployments and applications of the angulation mechanism were recorded, along with the reasons for use. Results: Technical success of the TEVAR was 97.6% owing to unintentional partial coverage of supra-aortic branches in 3 cases (the vessels were patent on imaging). The stent-graft was repositioned at its intermediate diameter in 79 patients (62.2%), and the angulation feature was applied in 64 cases (50.4%), mainly to improve proximal wall apposition and orthogonality in the aorta. The desired effect was achieved in 60 cases (93.8%). There was no device compression, bird-beak configuration, fracture, or graft occlusion. The 30-day and 12-month clinical success rates were 97.6% and 92.9%, respectively. There were 3 aorta-related deaths at 30 days and a further 3 at 12 months. Fatalities were due to a retrograde type A dissection (0.8%), paraplegia, bowel ischemia, sepsis in the setting of a mycotic aneurysm, aneurysm rupture post aortoesophageal fistula, and multiorgan dysfunction syndrome. Three endoleaks (2 type Ia and 1 type III) required reintervention. Conclusion: In the SURPASS registry, the use of the CTAG device with ACS showed promising outcomes despite the challenging pathologies. The new delivery system enables a controlled staged delivery with in situ adjustments during positioning, facilitating the treatment of complex aortic disease.

Off-the-Shelf Devices for Treatment of Thoracic Aortic Diseases: Midterm Follow-up of TEVAR With Chimneys or Physician-Made Fenestrations

Purpose: To evaluate the midterm outcomes of thoracic endovascular aortic repair (TEVAR) using chimney grafts (ch-TEVAR) or thoracic stent-grafts with fenestrations made on the back table (f-TEVAR) to treat thoracic aortic dissection (TAD) and thoracic aortic aneurysm (TAA). Materials and Methods: A retrospective analysis was conducted of 474 consecutive patients (mean age 62.3±10.7 years; 346 men) treated with either f-TEVAR (n=110) or ch-TEVAR (n=364) for 352 TADs (81 f-TEVAR and 271 ch-TEVAR) or 122 TAAs (29 f-TEVAR and 93 ch-TEVAR) from 2008 to 2016. The primary endpoints at 30 days and during follow-up were overall mortality, aorta-related mortality, and major complications. The secondary endpoints were endoleak and reintervention. The patency of the target branches, cost of hospitalization, and the use of antiplatelet drugs were also analyzed. Results: Intraoperative type I endoleaks were treated in 69 (14.6%) cases (4 f-TEVAR and 65 ch-TEVAR, p<0.01) to achieve 100% technical success. Four (0.8%) patients died within 30 days [1 (0.9%) f-TEVAR and 3 (0.8%) ch-TEVAR]. Perioperative cerebral ischemia (1 fatal stroke) occurred in 9 (1.9%) patients: (1 f-TEVAR and 8 ch-TEVAR, p=0.39). During the mean follow-up of 50.6±20.0 months (49.5±18.3 months in f-TEVAR and 50.9±20.6 months in ch-TEVAR), 11 (2.3%) patients died of an aorta-related event. Type I endoleak was present in 40 (8.4%) patients (1 f-TEVAR and 39 ch-TEVAR, p<0.01). Eleven (2.3%) patients experienced stent-graft migration and 13 (2.7%) had a retrograde dissection. One hundred (16.9%) of the 593 branch stents occluded (4/75 in the f-TEVAR group and 96/518 in the ch-TEVAR group, p<0.01). The branch reintervention rate was 7.2% (34/474). The f-TEVAR group had a significantly higher probability of freedom from branch occlusion (92%) than the ch-TEVAR group (83%, p=0.007). Conclusion: Off-the-shelf techniques employing chimney grafts and homemade fenestrations are both suitable options for TAD and TAA involving the supra-aortic branches, with a low incidence of reintervention. Fenestrated TEVAR seems to have more favorable short- and midterm outcomes. Further study of these off-the-shelf techniques for aortic arch repair is warranted.