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Coverage of the left subclavian artery (LSA) origin during thoracic endovascular aortic repair (TEVAR) is associated with increased neurologic complications. Our group is involved in the development of an off-the-shelf (OTS) thoracic endograft incorporating a left common carotid artery (LCCA) scallop and a retrograde inner branch for LSA perfusion. This study aimed to evaluate the arch morphology of patients treated by TEVAR and requiring LSA coverage to determine the applicability of this OTS device.The preoperative anatomy of consecutive patients from three separate cohorts treated with TEVAR with LSA coverage was studied. High-quality preoperative computed tomography angiography images were analyzed on an imaging workstation. Location of the origin of the supra-aortic trunks and their anatomic relationship were depicted in all patients; the LCCA origin was set as reference point. We determined the proportion of arch morphology in our cohort of patients eligible for this OTS device configuration.There were 196 patients included in this study, 132 in the dissection cohort and 64 in the aneurysm cohort. The median length from the lower margin of the LCCA to the proximal aspect of the pathologic process was 25.0 mm (18.2-35.2 mm), with 68.4% (n = 134) of our cohort presenting with a proximal sealing zone length20 mm. The median LCCA-LSA distance was 20.8 mm (16.6-25.4 mm). The median clock position of the LSA from the LCCA was -10 minutes (-30 to 0 minutes). In total, 127 patients (64.8%) could have been treated with the current OTS branched TEVAR configuration; 59 were excluded for proximal neck length distal to the LCCA 20 mm and 10 because of the clock position of the LCCA, and 9 first required a vertebral artery transposition.The low variability of LSA and LCCA locations in patients with distal aortic arch disease offers wide applicability of a new standardized thoracic branched endograft.

Objective The goal of this study was to select branched endograft designs that could fit most aortic arch anatomies. Such off-the-shelf endografts, once available, would be an endovascular therapeutic option to consider in the acute setting and would shorten the design and manufacturing process. Methods We retrospectively analyzed the endograft plans of all custom-made aortic arch branched endografts implanted between 2013 and early 2018 provided by the Cook Planning Center (EMEA Planning Services; Cook Medical, London, United Kingdom). Available data points of the endograft plans include proximal, intermediate, and distal endograft diameters; number of sealing stents; total length of the endograft; and number of branches. Results There were 286 two-branch endografts analyzed. We divided the endografts in three groups according to their proximal diameters: 34 mm, 36 mm, and 38 mm (group 1); 40 mm and 42 mm (group 2); and 44 mm and 46 mm (group 3). In group 1, 63% of the endografts had one proximal sealing stent, whereas in group 3, 63% had two proximal sealing stents. The distal diameters of the endografts ranged from 26 mm to 46 mm. The mean length was 236 mm (186-256 mm). A shorter standardized length of 211 mm was selected to anticipate distal extensions. According to our analysis, most group 1 patients could have been treated with a 38-mm proximal diameter and 30-mm distal diameter endograft with one sealing stent; most group 2 patients, with a 42-mm proximal diameter and 32-mm distal diameter endograft with both one and two proximal sealing stents; and most group 3 patients, with a 46-mm proximal diameter and 36-mm distal diameter endograft, also with both one and two proximal sealing stents. Conclusions Five standardized off-the-shelf endografts can cover a majority of aortic arch anatomies and offer an option for acute endovascular treatment of aortic arch disease.

Objective The aim of this study was to evaluate the feasibility and outcomes of endovascular repair of thoracoabdominal aortic aneurysms (TAAAs) using a novel low profile (LP) device with upper extremity preloaded guidewire system (PGS) and compare procedural metrics and outcomes with a standard multibranch stent graft (t-Branch; Cook Medical, Bloomington, Ind). Methods We reviewed the clinical data of 232 consecutive patients treated by fenestrated-branched endovascular aortic repair for TAAA and enrolled in a prospective nonrandomized trial between 2014 and 2017. Patients who had repair using t-Branch or patient-specific TAAA devices using upper extremity LP-PGS were included. End points were technical success, operative and fluoroscopic time, patient radiation exposure, time from arterial access to complete device deployment, total contrast volume, and 30-day rates of major adverse events (MAEs) and mortality. Results There were 54 patients, including 33 males (67%) and 21 females (33%), with a mean age of 73 ± 9 years old. Forty-nine patients (91%) had extent I-III and five patients (9%) had extent IV TAAAs. Device design was t-Branch in 24 patients (44%) and LP-PGS in 30 patients (56%). A total of 206 renal-mesenteric arteries were incorporated with no difference between groups (mean, 3.8 ± 0.6 target vessels/patient; P = .92). Patients treated by t-Branch device had larger mean aneurysm diameter (79 ± 16 vs 66 ± 10 mm; P = .0006). All patients had transbrachial approach. Technical success was achieved in all patients in both groups. Patients treated by LP-PGS devices had lower radiation dose (1250 ± 849 vs 3154 ± 2421 mGy; P = .003) and shorter operating time for complete device deployment (105 ± 42 vs 123 ± 34 minutes; P = .043). There was no difference in mean operative time (252 ± 69 vs 273 ± 56 minutes; P = .23), fluoroscopy time (82 ± 29 vs 96 ± 35 minutes; P = .08) or contrast volume (163 ± 59 vs 197 ± 75 mL; P = .07) comparing LP-PGS and t-Branch respectively. There was no 30-day or in-hospital mortality. There were no differences in MAEs, which occurred in 18 patients (33%) in both groups (P > .05). Conclusions Endovascular TAAA repair using the standard or LP-PGS multibranch stent graft was associated with high technical success, no mortality, and a low rate of MAEs in this study. Patients treated by upper extremity LP-PGS had shorter time to complete device deployment, suggesting decreased technical demand with preloaded systems.

Objective We evaluated the outcomes of total endovascular aortic arch repair using three-vessel inner branch stent-grafts for aneurysms and chronic dissections. Methods We reviewed the clinical data and outcomes of consecutive patients treated by total endovascular aortic arch repair at eight academic centers using three-vessel inner branch stent-grafts (William Cook Europe, Bjaeverskov, Denmark) from 2016 to 2019. All patients received three-vessel designs with two antegrade and one retrograde inner branch, which was used to incorporate the innominate, left common carotid, and left subclavian arteries. The antegrade inner branches were accessed via a carotid or an upper extremity approach. A preloaded catheter was used for access to the retrograde left subclavian artery branch via a transfemoral approach. The endpoints were technical success, mortality, major adverse events, any stroke (minor or major) or transient ischemia attack, secondary interventions, target vessel patency, target vessel instability, aneurysm-related mortality, and patient survival. Results A total of 39 patients (31 men [79%]; mean age, 70 ± 7 years) had undergone treatment of 14 degenerative (36%) and 25 chronic (64%) postdissection arch aneurysms. The clinical characteristics included American Society of Anesthesiologists class ≥III in 28 patients (95%) and previous median sternotomy for ascending aortic repair in 28 patients (72%). The technical success rate was 100%. Two patients had died in-hospital or within 30 days (5%), and two patients had experienced a stroke (one minor). The combined mortality and any stroke rate was 8% (n = 3). Major adverse events occurred in 10 patients (26%), including respiratory failure in 4 (10%) and estimated blood loss >1 L, myocardial infarction, and acute kidney injury in 2 patients each (5%). The median follow-up was 3.2 months (interquartile range, 1-14 months). Of the 39 patients, 12 (31%) required secondary interventions to treat vascular access complications in 5, endoleak in 6 (three type II, one type Ic, one type Ia/Ib, one type IIIa), and target vessel stenosis in 1 patient. At 1 year, the primary and secondary patency rates and freedom from target vessel instability were 95% ± 5%, 100%, and 91% ± 5%, respectively. Freedom from aortic-related mortality and patient survival was 94% ± 4% and 90% ± 6%, respectively. Conclusions The findings from the present multicenter global experience have demonstrated the technical feasibility and safety of total endovascular aortic arch repair for aneurysms and chronic dissections using three-vessel inner branch stent-grafts. The mortality and stroke rates compare favorably with those after open surgical repair in a higher risk group of patients. However, the rate of secondary interventions was high (31%), emphasizing need for greater experience and longer follow-up.

Purpose: To investigate the influence of (1) an additional side port for flushing the hollow pusher in Zenith thoracic stent-graft delivery systems and (2) additional carbon dioxide flushing on the amount of air released during stent-graft deployment. Methods: Twenty thoracic stent-grafts with an additional flush port to fill the hollow pusher were separated into 2 equal groups (C and D). Both groups were flushed with 20 mL of normal saline through the extra side port connected to the pusher and with 60 mL of saline through the regular flushing port. One group of grafts (group D) was additionally flushed with carbon dioxide through the regular flushing port prior to saline. All grafts were deployed into a curved plastic pipe attached to the bottom of a water-filled container. The released gas was recorded and measured using a calibrated setup. To evaluate the influence of the extra side port irrespective of the carbon dioxide flushing technique, group C was compared with a previously published reference group A without an extra side port that was flushed with the standard 60 mL of saline. Results: Volumes of gas were released in various amounts from the stent-grafts during deployment. The average amount of released gas was 0.51 mL in group C and 0.07 mL in group D (p

Mortality during follow-up after acute Type B aortic dissection is substantial with aortic expansion observed in over 59% of the patients. Lumen pressure differential is considered a prime contributing factor for aortic dilation after propagation. The objective of the study was to evaluate the relationship between changes in vessel geometry with and without lumen pressure differential post propagation in an ex vivo porcine model with comparison with patient clinical data. A pulse duplicator system was utilized to propagate the dissection within descending thoracic porcine aortic vessels for set proximal (%circumference of the entry tear: 40%, axial length: 2 cm) and re-entry (50% of distal vessel circumference) tear geometry. Measurements of lumen pressure differential were made along with quantification of vessel geometry (n = 16). The magnitude of mean lumen pressure difference measured after propagation was low (~ 5 mmHg) with higher pressures measured in false lumen and as anticipated the pressure difference approached zero after the creation of distal re-entry tear. False lumen Dissection Ratio (FDR) defined as arc length of dissected wall divided by arc length of dissection flap, had mean value of 1.59 ± 0.01 at pressure of 120/80 mmHg post propagation with increasing values with increase in pulse pressure that was not rescued with the creation of distal re-entry tear (p

Introduction The blood flow and stresses in the flap in aortic dissections are not well understood. Validated fluid–structure interaction (FSI) simulations of the interactions between the blood flow and the flap will provide insight into the dynamics of aortic dissections and may lead to developments of novel therapeutic approaches. Methods A coupled, two-way blood flow and flap wall computational model was developed. The Arbitrary Lagrange–Eulerian method was used, which allowed the fluid mesh to deform. Inflow velocity waveforms from a pulse duplicator system were used in the simulations. Results The velocities for true lumen (TL) and false lumen (FL) were not significantly different between bench and simulation. The dynamics of the TL % cross-sectional area (CSA) during the cycle was similar between the bench and computational simulations, with the TL %CSA being most reduced near peak systole of the cycle. The experimental distal measurements had significantly lower velocities, likely due to the spatially heterogeneous flow distally. The conservation of mass and validity of simulations were confirmed. Additionally, regions of stress concentrations were found on the flap leading edge, towards the corners, and through the entire vessel wall. The pressure gradient across the FL results in a net force on the flap. Conclusion The FSI flow velocities in the TL and the FL as well as the dynamics of the CSA during the cardiac cycle were validated by bench experiments. The validated FSI model may provide insights into aortic dissection including the stresses on the dissection flap and related flow disturbance, which may be subdued by novel therapeutic approaches. Simulations of more realistic human aortic dissections and the effects of current therapeutic approaches such as stent-graft can be developed in the future using the validated computational platform provided in the present study.

ObjectiveTo evaluate folding in infrarenal stent grafts in relation to oversizing, barb angle, and barb length using computed tomography images of stent grafts deployed in explanted bovine aortas.MethodsComputed tomography data from an in vitro investigation on the effect of oversizing of 4% to 45% (n = 19), barb length of 2 to 7 mm (n = 11), and barb angle of 10° to 90° (n = 7) on device fixation were examined for instances of folding. Folding was classified as circumferential or longitudinal and quantified on an ordinal scale based on codified criteria. Cumulative fold ranking from 0 (no fold) to 6 (two severe folds) for each deployment was used as the measure of folding observed.ResultsOf the 37 cases, cumulative mean ± standard deviation fold ranking for stent grafts oversized >30% (n = 5) was significantly greater than the rest (3.4 ± 1.7 vs 0.5 ± 1.2, respectively; Mann-Whitney U test; P < .005). When barb length was varied from 2 to 7 mm (oversizing held at 10%-20%), folding was noted in one of 11 cases. Similarly, when barb angle was varied from 0° (vertical) to 90° (horizontal), folding was not noted in any of the seven cases. The pullout force was not significantly different between stent grafts with and without folding (5.4 ± 1.95 vs 5.12 ± 1.89 N, respectively; P > .5). At least one instance of folding was noted in the seven of seven (100%) stent grafts with oversizing >23.5% and in only five of 30 (14%) stent grafts with oversizing 30%. Large variations in barb length and angle did not aggravate folding risk when oversized within the recommended range of 10% to 20%.Clinical RelevanceIn endovascular repair, a better understanding of the nature of stent graft deployment can improve treatment outcomes and device design. Folding of stent grafts affects graft apposition and, consequently, performance. In this study, the roles played by key stent graft variables on the propensity for folding were assessed in a controlled in vitro setting.

Purpose To test the hypothesis that ruptured abdominal aortic aneurysms (AAA) are globally weaker than unruptured ones. Methods Four ruptured and seven unruptured AAA specimens were harvested whole from fresh cadavers during autopsies performed over an 18-month period. Multiple regionally distributed longitudinally oriented rectangular strips were cut from each AAA specimen for a total of 77 specimen strips. Strips were subjected to uniaxial extension until failure. Sections from approximately the strongest and weakest specimen strips were studied histologically and histochemically. From the load-extension data, failure tension, failure stress and failure strain were calculated. Rupture site characteristics such as location, arc length of rupture and orientation of rupture were also documented. Results The failure tension, a measure of the tissue mechanical caliber was remarkably similar between ruptured and unruptured AAA (group mean±standard deviation of within-subject means: 11.2±2.3 versus 11.6±3.6 N/cm; p =0.866 by mixed model ANOVA). In post-hoc analysis, there was little difference between the groups in other measures of tissue mechanical caliber as well such as failure stress (95±28 versus 98±23 N/cm 2 ; p =0.870), failure strain (0.39±0.09 versus 0.36±0.09; p =0.705), wall thickness (1.7±0.4 versus 1.5±0.4 mm; p =0.470) , and % coverage of collagen within tissue cross section (49.6±12.9% versus 60.8±9.6%; p =0.133). In the four ruptured AAA, primary rupture sites were on the lateral quadrants (two on left; one on left-posterior; one on right). Remarkably, all rupture lines had a longitudinal orientation and ranged from 1 to 6 cm in length. Conclusion The findings are not consistent with the hypothesis that ruptured aortic aneurysms are globally weaker than unruptured ones.

Biomechanical issues of practical relevance to the physician in the clinical management of patients undergoing endovascular repair (EVR) of their abdominal aortic aneurysms (AAA) is discussed. Following a brief description of key terms in vascular biomechanics, background on the current state of knowledge in the biomechanics of AAA pathogenesis and rupture is provided. This is followed by a discussion of key issues of biomechanical relevance in EVR such as the mechanics of endotension, the notion of intraaneurysmal sac pressure and potential pitfalls of techniques used to measure them, mechanics of graft fracture/kinking, and graft migration. The discussions are intended to provide an overview of this field to physicians.

Rupture of abdominal aortic aneurysm (AAA) is a poorly understood phenomenon. Some aneurysms rupture as they grow larger, while many very large ones do not. There have been numerous reports on the failure properties of unruptured AAA [1], but similar data on ruptured AAA is scarce. Some reports suggest that greater pressure-induced tension in the AAA wall may predispose some to rupture [1]. But what of failure properties? It is conceivable that aneurysms which rupture are globally weaker than ones that do not or perhaps have very localized weak spots. Such key issues have not been explored because of lack of specimens from ruptured AAA. In this exploratory study between clinical and engineering investigators, unruptured and ruptured AAA were wholly harvested from fresh cadavers and the regional variations in wall thickness, mechanical properties and cellular content were compared.Copyright © 2009 by ASME

Endovascular repair of abdominal aortic aneurysm (AAA), where an endovascular graft (EVG) — a stented vascular graft — is implanted intraluminally into the AAA has shown excellent short term outcome. However, long term outcome of implanted EVGs is fraught with new complications, the most severe of which is endoleak from graft migration, which can lead to re-pressurization of the AAA and potentially rupture. Graft migration is defined as the distal drift of an implanted EVG of 5mm or more from its initial anchor site (Figure 1). There have been many design changes to help decrease the rate of EVG migration including the addition of proximal attachment barbs to grafts to help secure them to the aortic wall. However, studies show that freedom from migration rates have not significantly increased for those grafts containing barbs compared to grafts without barbs [1]. We believe that controlled studies of endovascular graft parameters can lead to improvements in its design that increase graft attachment strength and hence decrease the risk of migration. The aim of the current study was to assess a key design variable in barbed grafts namely, graft oversizing (GO), defined as the ratio of expanded graft dia to aorta dia. We sought to assess the relationship between GO and attachment strength in barbed EVGs. Specifically, we hypothesized that a high GO will impede the ability of the EVG barbs to effectively penetrate the aortic wall.

Characterizing the material symmetry of a biological soft tissue can aid in understanding and modeling its mechanics. Optical methods have been reported for identification of structural fiber orientations in thin tissues such as heart valve leaflets [1], but not in thick tissues such as arteries because optical methods are not as effective with thick tissues. Besides fiber architecture, effective transmural material symmetry of a planar tissue needs to be known a priori in order to perform and interpret common testing methods such as planar biaxial testing or inflation testing (for cylindrical specimens). Nielsen et al. [2] reported on planar radial testing to study inhomogeneous properties of elastic membranes. We submit that planar radial extension testing (PRET) of a thick circular soft tissue specimen will reveal the underlying material symmetry. We performed numerical simulations of planar radial extension testing and assessed its feasibility using a simple custom-fabricated device.Copyright © 2007 by ASME

The regional distribution of wall thickness and failure properties in human abdominal aortic aneurysm (AAA) was explored. Three unruptured and one ruptured AAA were harvested as a whole during necropsy. Thickness was measured at about every 1.5 cm(2) wall surface area for an average of 100 measurement sites per AAA. Multiple longitudinally oriented rectangular specimen strips were cut at various locations from each AAA for a total of 48 strips. The strips were subjected to uniaxial extension until failure. Wall thickness varied regionally and between AAA from as low as 0.23 mm at a rupture site to 4.26 mm at a calcified site (median=1.48 mm). Wall thickness was slightly lower in the posterior and right regions. The failure tension (ultimate) of specimen strips varied regionally and between AAA from 5.5 N/cm close to a blister site in the ruptured AAA to 42.3N/cm at the undilated neck of a 4 cm diameter unruptured AAA (median=14.8 N/cm). Failure stress (ultimate) varied from 33.6 to 235.1N/cm(2) (median=126.6N/cm(2)). There was no perceptible pattern in failure properties along the circumference. Failure tension of specimen strips at or close to blisters was mostly low. The rupture site in the ruptured aneurysm had the lowest recorded wall thickness of 0.23 mm with only slightly higher readings within a 1cm radius. The failure tension of the specimen strip close to the rupture site was low (11.1 N/cm) compared to its neighborhood in the ruptured aneurysm.

Computed Tomography (CT) and Magnetic Resonance (MR) imaging techniques have become an important role in diagnosing the vascular diseases. Before a clinical trial of the newly developed techniques, it is essential to evaluate them on a phantom. However, there is no existing arterial tree phantom that serves for flood flows. To that end, we design and develop a Dynamic Arterial Tree Phantom (DATP), which is able to produce many kinds of blood flow pattern through using a programmable pump functions as a heart. Contrast enhanced CT scan is also performed on this phantom for adaptive bolus chasing techniques.