Evolution and Future of Preclinical Testing for Endovascular Grafts

Abstract

The preclinical testing of endovascular grafts has evolved significantly since the creation and early testing of these devices; however, there are continued limitations in using preclinical testing to predict clinical performance. Early testing was conducted in the absence of standards and guidance specific to endovascular grafts, and references available for vascular grafts and stents did not adequately account for the complexity of endovascular graft systems. Failure of early-generation devices suggested that the testing being conducted was inadequate and that there was a lack of understanding of the in vivo environment. These concerns led to several efforts to improve preclinical testing. The Food and Drug Administration (FDA) sponsored a workshop to discuss the limitations inherent in testing of endovascular grafts, and an ISO standard for endovascular grafts was developed. Publication of the standard in 2003 succeeded in standardizing testing and reporting across device manufacturers; however, several clinical failure modes, such as migration and stent fractures, continued to be unpredicted by current preclinical testing. This, coupled with knowledge gained from additional clinical experience, led the FDA to hold a second workshop to discuss the benefits and limitations of current testing and propose future testing that may better predict device performance. This workshop was successful in accurately describing past testing, determining what has been learned, identifying issues that have not been adequately addressed, proposing modifications to address these limitations, and discussing how the proposed modifications should be implemented. While significant progress has been made in endovascular graft testing, continued collaboration among industry, academia, regulators, and clinicians will provide continued improvement in the predictability of device performance.

An in Vitro Twist Fatigue Test of Fabric Stent-Grafts Supported by Z-Stents vs. Ringed Stents

“…However, twisting may cause yarn shifting, possibly allowing blood percolation through the fabric. Percolation of low volumes of blood through multiple sites of damage to the fabric may explain the endotension phenomenon [59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84]. …”

Imagerie des flux aortiques par IRM et mécanique des fuides: applications cliniques sur la pathologie aortique thoracique

“…Une autre application est l'évaluation des stents grafts thoraciques. En effet, les différents constructeurs ont proposé des modèles in vitro pour évaluer leurs dispositifs mais la plupart de ces évaluations sont souvent très loin de la réalité à la fois sur le plan de l'anatomie que sur le plan des caractéristiques physiologiques de ces modèles (24). L'intérêt des CFD est d'évaluer sur des patients, les différents matériels qui peuvent être utilisés pour analyser la réponse entre la prothèse et la paroi aortique mais également pour analyser les mouvements et les forces pariétales exercées par le flux sanguin au sein du stent graft et ainsi d'apprécier les risques de lésions de fatigue du matériel ( fig.…”

Comparative Study of Two Surgically Created Swine Models of Abdominal Aortic Aneurysm

“…All new devices need to be evaluated, as preclinical testing may be useful to screen out poor designs prior to clinical use, and after the first clinical trials animal testing could help in analysing clinically observed failures and in evaluating device modifications. 7 Minimally Invasive procedures for AAA therapy, including laparoscopy, 8 are relatively new, and are therefore still under development. An animal model of AAA that could be used both in research and training in these procedures would be helpful in defining the role of each technique, as well as in exploring future possibilities, such as combined therapies, both in terms of combining endovascular with laparoscopic approaches and in regards to the use of drug-eluting stent grafts.…”

“…An animal model of AAA that could be used both in research and training in these procedures would be helpful in defining the role of each technique, as well as in exploring future possibilities, such as combined therapies, both in terms of combining endovascular with laparoscopic approaches and in regards to the use of drug-eluting stent grafts. 7 It has been recommended that animal studies of endovascular grafts focus on the assessment of the delivery systems and biological responses to the device. 7 Different animal models of AAA have been described in the literature.…”

“…7 It has been recommended that animal studies of endovascular grafts focus on the assessment of the delivery systems and biological responses to the device. 7 Different animal models of AAA have been described in the literature. 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 However, many of them are not adequate for assessing tissue incorporation or inflammatory responses to deployed grafts, having been created with either synthetic 9 , 10 , 16 or treated 15 tissues.…”