Auswahl der wissenschaftlichen Literatur zum Thema „Vascular endograft“

The number of endovascular aortic repairs (EVARs) has surpassed the number of open surgical repairs of abdominal aortic aneurysms (AAAs) worldwide. The available commercial endoprostheses are composed of materials that are stiffer than the native aortic wall. As a consequence, the implantation of stent–graft endoprostheses during EVAR increases aortic rigidity and thus aortic stiffness, resulting in a decrease in abdominal aorta compliance. EVAR has been found to have a possibly harmful effect not only on heart functions but also on other vascular beds, including kidney function, due to the decrease in aortic compliance that it causes. Aortic stiffness is measured by various hemodynamic indices like the pulse wave velocity (PWV), the central aortic pressure (CAP), and the augmentation index (AIx). In the literature, there are increasing numbers of studies investigating the properties of endografts, which are strongly related to increases in aortic stiffness. However, there is a lack of data on whether there is a correlation between the length of various endografts implanted during EVAR and the increase in the PWV, CAP, and AIx postoperatively compared to the preoperative values. The aim of this prospective, observational, monocentric, single-arm study is to investigate the correlation between endograft length and the postoperative increase in the PWV, CAP, and AIx in patients subjected to EVAR. Additionally, this study intends to identify other endograft properties related to increases in the PWV, CAP, and AIx. Other endpoints to be studied are the existence of immediate postoperative myocardial and kidney injury after EVAR. The prediction of cardiovascular events caused by endograft-related increased aortic stiffness could contribute to the improvement of various endograft properties so that the impact of endografts on the native aortic wall can be minimized.

Purpose: To compare the impact of 2 commercially available custom-made fenestrated endografts on patient anatomy. Materials and Methods: The records of 234 patients who underwent fenestrated endovascular aneurysm repair for abdominal aortic aneurysm from March 2002 to July 2016 in 2 hospitals were screened to identify those who had pre- and postoperative computed tomography angiography assessments with a slice thickness of ≤2 mm. The search identified 145 patients for further analysis: 110 patients (mean age 72.4±7.1 years; 94 men) who had been treated with the Zenith Fenestrated (ZF) endograft and 35 patients (mean age 72.3±7.3 years; 30 men) treated with the Fenestrated Anaconda (FA) endograft. Measurements included aortic diameters at the level of the superior mesenteric artery (SMA) and renal arteries, target vessel angles, target vessel clock positions, and the target vessel tortuosity index. Variables were tested for inter- and intraobserver agreement. Results: There was a good agreement between observers in all tested variables. The native anatomy changed in both groups after endograft implantation. In the ZF group, changes were seen in the angles of the celiac artery (p=0.012), SMA (p=0.022), left renal artery (LRA) (p<0.001), and the right renal artery (RRA) (p<0.001); the aortic diameter at the SMA level (p<0.001); and the LRA (p<0.001) and RRA (p<0.001) clock positions. In the FA group, changes were seen in the angles of the LRA (p=0.001) and RRA (p<0.001) and in the SMA tortuosity index (p=0.044). Between group differences in changes were seen for the aortic diameters at the SMA and renal artery levels (p<0.001 for both) and the LRA clock position (p=0.019). Conclusion: Both custom-made fenestrated endografts altered vascular anatomy. The data suggest a higher conformability of the Fenestrated Anaconda endograft compared with the Zenith Fenestrated.

Purpose: To summarize the results of endovascular abdominal aortic aneurysm (AAA) treatment using several endograft designs over a 4.5-year experience and offer comparisons on the various devices. Methods: From May 1992 to August 1996, 121 AAA patients meeting the criteria for an endoluminal repair were treated with 1 of 5 endograft designs in three configurations. The endografts were implanted in the operating room under fluoroscopic control. Follow-up included contrast-enhanced computed tomography within 10 days of operation, 6 months postoperatively, and annually thereafter. Results: Endografts were successfully deployed in 106 patients (88%). Fifteen cases were converted to open repair. Six procedure-related deaths occurred within 30 days owing to myocardial infarction (3), combined renal failure and septicemia (2), and multisystem failure (1). There were 36 local/vascular complications (30%) and 18 systemic/remote complications (15%). Of the 121 patients undergoing endoluminal AAA repair, 93 (77%) are currently alive and well with their AAAs excluded from the circulation. Conclusions: Trends in endoluminal AAA repair and prosthetic design point toward simpler devices and earlier treatment of smaller aneurysms once the long-term outcome of aortic endografting has been determined.

Purpose: The aim of this study was to report early experiences with the Sydney and Endovascular Technologies (EVT) prostheses for the treatment of abdominal aortic aneurysms (AAA) deemed suitable for endoluminal tube graft repair. Methods: Consecutive endoluminal tube graft repairs were analyzed over the first 12 months in which the Sydney and EVT prostheses were used. Patients eligible for the EVT prosthesis had type I AAAs: a proximal neck length ≥ 2 cm, a distal cuff length ≥ 1.5 cm, and nontortuous iliac arteries ≥ 8 mm. Selection criteria for the Sydney device were more liberal and included AAAs that had distal cuffs < 1.5 cm. During the study period, 28 of 91 patients evaluated for AAA repair were thus selected for endoluminal grafting: 18 patients received the Sydney endograft and 10 the EVT device. Medical comorbidities were present in slightly less than one third of patients in both groups. Contrast-enhanced computerized tomography (CT) was performed preoperatively, within 10 days of operation, and at 6 and 12 months postprocedure. Results: All endografts were successfully deployed in both groups. Postprocedural CT scans revealed incomplete aneurysm exclusion in four patients with the Sydney endograft. Subsequent deployment of a second endograft sealed these “leaks” in two cases; the other two were converted to open repair (89% clinical success). No leaks were seen with the EVT device. Local/vascular complications occurred in 33% of the Sydney group compared with 20% for the EVT device (p = 0.001); systemic sequelae were more common in the EVT group (30% versus 17% in the Sydney cohort, p = 0.002). There were no deaths within 30 days; three late deaths were not procedure related. Conclusion: AAAs that are suitable for endoluminal tube graft repair may be treated with a high rate of initial success with either the Sydney or EVT prostheses. More liberal selection criteria may increase the likelihood of local/vascular complications.

Purpose: To describe the deployment technique, function, and gross healing of an endoluminal vascular prosthesis deployed in a high-risk patient for treatment of a common iliac artery (CIA) aneurysm. Methods: An 82-year-old, high-risk male with a 4-cm-diameter CIA aneurysm approximately 4.5 to 5 cm long was treated with endoluminal exclusion of the lesion using a 6-cm-long, 14-mm-internal diameter Dacron vascular prosthesis with Palmaz 308 stents sutured to either end of the graft. Intravascular ultrasound (IVUS) imaging facilitated sizing of the endograft and its accurate positioning so as to occlude both the aneurysm and the hypogastric artery, which was a potential source of retrograde flow to the aneurysm. Exclusion of the lesion and occlusion of the hypogastric artery were demonstrated on delayed angiographic images and contrast computed tomography scans obtained at 16 days postprocedure. Unfortunately, the patient died 67 days following implantation from a nonprocedure-related gastrointestinal complication. Results: At autopsy, the aortoiliac segment was excised and examined grossly and histologically; the evaluation confirmed complete isolation of the aneurysm by the fully expanded endoluminal prosthesis. The surface of the vascular graft was covered by a glistening, thin, fibrinous membrane. The graft material was filled with hypocellular compact fibrinous material with no evidence of endothelialization. These observations confirm preliminary sealing and isolation of the iliac artery aneurysm as healing of the endograft progressed. Conclusions: The data acquired from the analysis of this specimen provide information regarding the utility and early healing of an endograft used for iliac artery aneurysm exclusion. This case also exemplifies the utility of IVUS in endograft deployment.

Purpose: This study investigated the effect of different EndoAnchor configurations on aortic endograft displacement resistance in an in vitro model. Materials and Methods: An in vitro model was developed and validated to perform displacement force measurements on different EndoAnchor configurations within an endograft and silicone tube. Five EndoAnchor configurations were created: (1) 6 circumferentially deployed EndoAnchors, (2) 5 EndoAnchors within 120° of the circumference and 1 additional, contralateral EndoAnchor, (3) 4 circumferentially deployed EndoAnchors, (4) 2 rows of 4 circumferentially deployed EndoAnchors, and (5) a configuration of 2 columns of 3 EndoAnchors. An experienced vascular surgeon deployed EndoAnchors under C-arm guidance at the proximal sealing zone of the endograft. A constant force with increments of 1 newton (N) was applied to the distal end of the endograft. The force necessary to displace a part of the endograft by 3 mm was defined as the endograft displacement force (EDF). Two video cameras recorded the measurements. Videos were examined to determine the exact moment 3-mm migration had occurred at part of the endograft. Five measurements were performed after each deployed EndoAnchor for each configuration. Measurements are given as the median and interquartile range (IQR) Q1, Q3. Results: Baseline displacement force measurement of the endograft without EndoAnchors resulted in a median EDF of 5.1 N (IQR 4.8, 5.2). The circumferential distribution of 6 EndoAnchors resulted in a median EDF of 53.7 N (IQR 49.0, 59.0), whereas configurations 2 through 5 demonstrated substantially lower EDFs of 29.0 N (IQR 28.5, 30.1), 24.6 N (IQR 21.9, 27.2), 36.7 N, and 9.6 N (IQR 9.4, 10.0), respectively. Decreasing the distance between the EndoAnchors over the circumference of the endograft increased the displacement resistance. Conclusion: This in vitro study demonstrates the influence EndoAnchor configurations have on the displacement resistance of an aortic endograft. Parts of the endograft where no EndoAnchor has been deployed remain sensitive to migration. In the current model, the only configuration that rivaled a hand-sewn anastomosis was the one with 6 EndoAnchors. A circumferential distribution of EndoAnchors with small distances between EndoAnchors should be pursued, if possible. This study provides a quantification of different EndoAnchor configurations that clinicians may have to adopt in clinical practice, which can help them make a measured decision on where to deploy EndoAnchors to ensure good endograft fixation.

Purpose: To validate new computed tomography (CT)–applied software used to determine endograft limb position and apposition after endovascular aneurysm repair (EVAR). Materials and Methods: Twelve EVAR patients (mean age 81±6 years; 10 men) with distal stent-graft extensions for 15 (3 bilateral) type Ib endoleaks during follow-up were selected based on the availability of the following CT studies: pre-EVAR, 1 month, and the penultimate scan prior to the scan disclosing the type Ib endoleak. Twelve patients (mean age 82±7 years; 11 men) without endoleak and a similar interval between the primary EVAR procedure and the penultimate CT scan of the endoleak group were selected as controls using measurements from both endograft limbs (n=21, 3 excluded). Prototype Vascular Imaging Analysis software was adapted to calculate 6 parameters for the distal apposition zone: fabric distance, shortest apposition length, endograft diameter, iliac seal surface (ISS), iliac endograft apposition surface (IEAS), and percentage of iliac surface coverage (IEAS/ISS × 100). Measurements were performed on the preoperative, first postoperative, and penultimate/matched follow-up CT scans. Interobserver variability was assessed with the intraclass correlation coefficient (ICC). Continuous data are presented as the median [interquartile range (IQR) Q1, Q3]. Results: CTA follow-up was not significantly different between the endoleak and control groups [30 months (IQR 18, 58) vs 36 months (IQR 21, 59), p=0.843]. Interobserver agreement was good to excellent for all parameters (ICC 0.879–0.985). Preoperative anatomy and endograft dimensions on the first follow-up CTA scan did not differ significantly between the groups. When the penultimate CTA scan was compared with the first postoperative CT scan, endograft dimensions had significantly changed in the endoleak group; importantly, apposition was significantly decreased, and fabric distance was significantly increased, indicating limb retraction. Differences in changes in endograft dimensions were significant between the groups. Conclusion: New CT-applied software was introduced to visualize apposition and position changes of endograft limbs during follow-up. The software demonstrated good-to-excellent interobserver agreement and enabled accurate analysis of post-EVAR endograft dimensions. Significant changes in apposition and position were observed with the software on the penultimate CT scan prior to diagnosis of type Ib endoleak.

Hypovolemia-induced hypotension may lead to an aortic diameter decrease in patients with a ruptured abdominal aortic aneurysm (rAAA). This study investigates the changes in supra- and infra-renal aortic neck diameters before and after endovascular aortic aneurysm repair (EVAR) for rAAA and the possible association with endograft apposition. A retrospective cohort study was conducted including 74 patients treated between 2010 and 2019 in two large European vascular centers. Outer-to-outer wall diameters were measured at +40, +10, 0, −10, and −20 mm relative to the lowest renal artery baseline on the last pre- and first post-EVAR computed tomography angiography (CTA) scan in a vascular workstation. Endograft apposition was determined on the first post-EVAR CTA scan. The post-operative diameter was significantly (p < 0.001) larger than the preoperative diameter at all aortic levels. The aortic diameter at +40 mm (supra-renal) and −10 mm (infra-renal) increased by 6.2 ± 7.3% and 12.6 ± 9.8%, respectively. The aortic diameter at +40 mm increased significantly more in patients with low preoperative systolic blood pressure (<90 mmHg; p = 0.005). A shorter apposition length was associated with a higher aortic diameter increase (R = −0.255; p = 0.032). Hypovolemic-induced hypotension results in a significant decrease in the aortic diameter in patients with an rAAA, which should be taken into account when oversizing the endograft.

Purpose: To document whether the vasodilatory response seen at the anastomotic segment 6 months after placement of a balloon-expandable endograft in the femoropopliteal segment progresses between 6 and 24 months. Methods: Twelve patients (9 men; median age 65 years, range 47–75) treated with an investigational polytetrafluoroethylene (PTFE) endograft for obstructive disease of the femoropopliteal segment were studied with intravascular ultrasound (IVUS) immediately after placement and at 6 months (first follow-up period) and 24 months (second follow-up period). Matched IVUS cross sections derived from the endograft and the anastomotic segment were analyzed for changes in lumen (LA), vessel (VA), and plaque areas (PLA). Results: Five patients had complete IVUS surveillance at both the first (mean 8 months, range 7–9) and second (mean 25 months, range 23–26) follow-up periods; 1 patient was lost to follow-up during the second interval, and another 6 were excluded owing to graft occlusion (n = 4) or no IVUS surveillance available (n = 2) during the second follow-up period. Matched IVUS cross sections derived from the endograft showed no significant change in LA during both follow-up periods (–8% and +1%, respectively). There was no evidence for intimal hyperplasia or endograft recoil. During both follow-up periods, IVUS cross sections derived from the anastomotic segment revealed significant increases in LA (+37% and +8%, respectively) and VA (+26% and +6%, respectively) (both p < 0.05). The change in PLA during both follow-up periods was not significant (+13% and +3%, respectively). Conclusions: The PTFE endograft seems to inhibit both intimal hyperplasia and constrictive remodeling. The short-term (6-month) vascular dilatory response seen at the anastomotic segment tends to stabilize at 2 years. Therefore, this endovascular anastomosis acts as an “ideal” end-to-end anastomosis.

Purpose: To report the results of a postmortem examination in a patient who died of unrelated causes 7 months following endoluminal treatment of an infrarenal abdominal aortic aneurysm (AAA). Methods: As part of an FDA Phase I pilot study, a 73-year-old man underwent successful endoluminal exclusion of an infrarenal AAA using a 9-cm-long endograft (Endovascular Grafting System). Seven months later, he succumbed to complications of a spontaneous esophageal rupture. At autopsy, the aorta was dissected in situ by a vascular surgeon and pathologist before being explanted in order to examine the wound healing characteristics at the aorta-endograft interface. Particular attention was also directed to the hooks composing the attachment system at each end of the endograft. Results: Macroscopic and microscopic examination revealed that the graft had completely excluded the aneurysm sac from the circulation and was incorporated into the aortic wall at the proximal neck and distal cuff. A smooth pannus of endothelial cells covered the proximal end of the endograft at the areas of contact with the aorta, while microscopic examination of the distal end of the graft revealed poorly formed, fibrinous pannus. The neointima deep to the endothelium consisted of a collagenous matrix containing myofibroblasts and histiocytes, providing evidence of healing between the endograft and aorta. Both renal arteries were clear of the proximal end of the endograft, but a previously unrecognized right lower pole renal artery with an extremely caudal origin was excluded from the aortic lumen. Each hook of the attachment system was seen protruding through the adventitia of the aorta. There was no evidence of trauma to the aortic wall or the surrounding tissues caused by these hooks. Conclusion: There appears to be evidence that an endoluminally placed aortic graft may be incorporated by the host aortic tissue.

La réparation endovasculaire (EVAR) d'un anévrisme de l'aorte abdominale (AAA) consiste en la mise en place d'une endoprothèse (EDP) par chirurgie mini-invasive au sein de l'anévrisme. Cet acte permet de prévenir la rupture des tissus endommagés impliqués dans un AAA, défini comme la dilatation localisée du diamètre de l'aorte. Lorsque l'amont de l'anévrisme englobe les artères périphériques rénales et/ou viscérales, l'AAA est qualifié de complexe. Dans ce cas, l'EDP déployée est dite « fenêtrée », en d'autres termes, perforée à l'emplacement des jonctions vers les artères périphériques. La prise en charge dans le cadre d'un AAA complexe devient alors plus limitante car l'EDP fenêtrée sera conçue sur mesure afin de correspondre à l'anatomie de l'anévrisme et à la position des artères périphériques du patient. Cela implique un délai de fabrication de plusieurs semaines, limite la prise en charge aux anévrismes stables et exclut les situations d'urgence. Dans ce contexte, l'impression 3D présente un intérêt considérable pour la fabrication d'EDP sur mesure et dans des délais très courts. Ainsi, l'objectif de ce travail de thèse est de concevoir un prototype d'endoprothèse par impression 3D d'un polyuréthane thermoplastique (TPU) de grade médical (élastomère thermoplastique). Le présent travail permettra de valider le procédé de conception et la fonctionnalité de notre 3D-EDP pour son application finale en tant que dispositif médical implantable.Dans un premier temps, l'impact du procédé de fabrication sur les propriétés chimiques, physiques et physico-chimiques du TPU a été étudié à chaque étape, des granulés à la stérilisation par rayons gamma d'une prothèse fabriquée par dépôt de filament fondu (FDM). L'évaluation préliminaire in vitro de la cytotoxicité et de l'hémocompatibilité du TPU a été réalisée après l'étape d'impression 3D et de stérilisation. Un vieillissement préliminaire du TPU en conditions oxydantes extrêmes a été réalisé afin de prédire l'évolution de ses propriétés sur le long terme. Par la suite, une stratégie de conception d'un prototype implantable par voie endovasculaire a été développée. Les propriétés de ce prototype stérilisé ont été caractérisées par différentes techniques (CES, ATG, DSC, FTIR, MEB, goniométrie, traction uniaxiale, …). Ses propriétés biologiques ont été évaluées in vitro par des tests de cytocompatibilité, hémocompatibilité et contact avec les macrophages pendant 24 heures (inflammation aigüe). L'évolution de ses propriétés physico-chimiques et mécaniques a été suivie par des études de vieillissement in vitro.La caractérisation des propriétés chimiques, physiques et physico-chimiques du TPU a montré que l'impression 3D FDM et la méthode de stérilisation par rayons gamma constituent une voie de fabrication viable d'un prototype comprimable dans un cathéter d'introduction endovasculaire. L'évaluation biologique in vitro a montré la cytotocompatibilité du prototype par la méthode de l'extrait. De plus, le prototype s'est révélé faiblement hémolytique et les plaquettes adhérant à sa surface n'étaient pas activées. La faible sécrétion de cytokines (IL-6 et TNF-a) au contact des macrophages inactivés a montré que le prototype d'EDP ne présente pas de caractère pro-inflammatoire. Enfin, les études de vieillissement ont montré un impact sur les propriétés mécaniques et de surface de notre prototype d'EDP sans toutefois compromettre sa fonctionnalité. Par la suite, la stratégie de conception pourrait évoluer vers une fonctionnalisation de l'EDP afin de prévenir les infections et les thromboses responsables respectivement de 2% et 6% des complications post-opératoires
Endovascular repair (EVAR) of an abdominal aortic aneurysm (AAA) involves the placement into the aneurysm of a stent graft (SG) by minimally invasive surgery. This procedure prevents rupture of the damaged tissue involved in an AAA, defined as a localized diameter dilation of the aorta. When the upstream portion of the aneurysm includes the peripheral renal and/or visceral arteries, the AAA is qualified as complex. In this case, the deployed SG is said “fenestrated”, in other words, perforated at the site of junctions to the peripheral arteries. Management of a complex AAA becomes more limiting as the fenestrated SG will be custom designed to match the anatomy of the aneurysm and the position of the peripheral arteries of the patient. This implies a manufacturing delay of several weeks, limits the management to stable aneurysms and excludes emergency situations. In this context, 3D printing (3DP) is of considerable interest for the fabrication of custom-made SGs in a very short time frame. Thus, the objective of this thesis work is to design a SG prototype by 3D printing of a medical grade thermoplastic polyurethane (TPU) (thermoplastic elastomer). The present work will validate the manufacturing process and the functionality of our 3DP-SG for its final application as an implantable medical device.First, the impact of the manufacturing process on the chemical, physical and physicochemical properties of TPU was studied at each step, from the pellets to the gamma-ray sterilization of a graft manufactured by fused filament deposition (FDM). In vitro preliminary evaluation of the cytotoxicity and hemocompatibility of TPU was carried out after the 3D printing and sterilization step. Aging of TPU under extreme oxidizing conditions was performed to predict the evolution of its properties in the long term. Subsequently, a design strategy for an endovascular implantable prototype was developed. The properties of said prototype were characterized by different techniques (SEC, TGA, DSC, FTIR, SEM, goniometry, uniaxial traction, ...). Its biological properties were evaluated in vitro by tests of cytocompatibility, hemocompatibility and contact with macrophages for 24 hours (acute inflammation). Moreover, the evolution of its physicochemical and mechanical properties was evaluated by in vitro aging studies.The characterization of the chemical, physical and physicochemical properties of TPU enabled the validation of a FDM printing manufacturing route and gamma ray sterilization of a crimpable SG prototype. The in vitro biological evaluation showed the non-cytotoxicity of the SG prototype by the extraction method. Moreover, the prototype was found to be weakly hemolytic and the platelets adhered on its surface were not activated. The low secretion of cytokines (IL-6 and TNF-α) upon contact with inactivated macrophages showed that the SG prototype does not exhibit a pro-inflammatory characteristic. Finally, aging studies showed an impact on the mechanical and surface properties of our SG prototype without compromising its functionality. Subsequently, the design strategy could evolve towards a functionalization of the SG prototype in order to prevent infections and thrombosis responsible for 2% and 6% of postoperative complications respectively

A thin film nitinol covered endograft for vessel treatment was manufactured and in vivo swine testing was performed. Thin film nitinol graft material was fabricated by DC sputter deposition and stress-strain behavior and DSC characteristics were investigated. Micro size patterns were fabricated by MEMS technology in order to promote endothelial layer growth. In-vivo studies in swine were conducted to evaluate deployment, placement and patency of the implanted stent device.