Session: 07-05-01: Biomedical Devices, Sensors, and Actuators

Paper Number: 193270

Experimental Investigation to Evaluate Fatigue Behavior of Fenestrations in Endovascular Stent-Grafts 

Fenestrated endovascular grafts are used for the minimally invasive treatment of aortic pathologies such as aneurysms and dissections. These devices function by sealing the diseased vessel segment, preventing rupture while maintaining blood flow to branch vessels through openings known as fenestrations. Endovascular grafts are typically composed of polymeric textile graft materials reinforced with metallic stent structures. The structural integrity of these devices is essential because once implanted they are exposed to continuous physiological loading from pulsatile blood pressure and vascular motion throughout the patient’s lifetime. These loading conditions produce millions of cyclic stress cycles that can lead to fatigue damage, particularly in regions where the material structure is altered, such as at a fenestration. Understanding the mechanical durability of these localized structural modifications is therefore critical for ensuring long-term device performance and patient safety. The motivation of this work is to better characterize the mechanical reliability of endovascular graft fenestrations under cyclic physiological loading conditions. Fenestrations may be manufactured by the device producer or created intraoperatively by clinicians to accommodate patient-specific geometry of branch vessels. Despite the increasing clinical use of fenestrated endovascular grafts, current standardized durability testing methods for vascular implants primarily evaluate the overall device performance and do not specifically address fatigue behavior at fenestrations. This work proposes a fatigue test setup specifically designed to evaluate the reliability of manufactured graft fenestrations. The experimental system allows repeatable loading conditions and continuous monitoring of the mechanical response of the graft material during fatigue testing. In the present study, endograft specimens containing circular fenestrations with a diameter of 8 mm were subjected to cyclic radial loading at a frequency of 1.6 Hz with a displacement stroke of 14 mm. The selected loading frequency represents an accelerated testing condition relative to physiological cardiac pulsatile loading, which occurs at approximately 1 Hz, while also exceeding additional mechanical contributions such as respiratory-induced deformation that typically occurs in the range of approximately 0.13–0.27 Hz. This accelerated frequency allows rapid assessment of fatigue at the fenestration. Preliminary results indicate a decline in mechanical response, with an approximately 0.5 lb reduction in force response after 4480 seconds of testing. Measurements and observations during testing suggest progressive degradation in the structural response of the fenestration boundary as the number of loading cycles increases. For an unsupported fenestration, the surface area increased by approximately 30% over the testing period (4480 seconds) under the aforementioned testing conditions, expanding from 51.97 mm² to 67.68 mm². Future work will include expanded testing to statistically validate these preliminary findings and complementary evaluations such as radial force measurements and pulsatile durability testing which they will be conducted to further investigate the long-term structural reliability of fenestrated grafts under physiologically relevant loading conditions.

Presenting Author: Parsaoran Hutapea Temple University

Presenting Author Biography: Dr. Parsaoran Hutapea is a Professor in the Department of Mechanical Engineering. He received his BS, MS, and PhD all in Aerospace Engineering from North Carolina State University, Raleigh, North Carolina. He was a Postdoctoral Fellow in the Department of Mechanical Engineering and Mechanics at Lehigh University, Bethlehem, Pennsylvania. Dr. Hutapea is a Fellow of the American Society of Mechanical Engineers.

Authors:

Nikolaos Farfaras Temple University
Robert Gregory Conway Temple University
Parsaoran Hutapea Temple University