Failure properties of intraluminal thrombus in abdominal aortic aneurysm under static and pulsating mechanical loads

• Published in: Journal of vascular surgery 2008-07, Vol.48 (1), p.179-188
• Main Authors: Gasser, T. Christian, PhD, Görgülü, Göray, MSc, Folkesson, Maggie, MSc, Swedenborg, Jesper, MD, PhD
• Format: Article
• Language: English
• Subjects: Aortic Aneurysm, Abdominal - physiopathology; Aortic Rupture - physiopathology; Biological and medical sciences; biomechanics; Blood and lymphatic vessels; Cardiology. Vascular system; Culture Media; diameter; Diseases of the aorta; Elasticity; Endothelium, Vascular - physiopathology; Finite Element Analysis; growth; high-attenuating crescent; Medical sciences; Medicin och hälsovetenskap; Models, Cardiovascular; Pulsatile Flow; risk; rupture; sign; Stress, Mechanical; Surgery; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Tensile Strength; Thrombosis - physiopathology; Vascular surgery: aorta, extremities, vena cava. Surgery of the lymphatic vessels; wall stress
• ISSN: 0741-5214; 1097-6809; 1097-6809
• DOI: 10.1016/j.jvs.2008.01.036

Objectives It has been suggested that mechanical failure of intraluminal thrombus (ILT) could play a key role in the rupture of abdominal aortic aneurysms (AAAs), and in the present study, this hypothesis has been investigated. An in vitro experimental approach has been proposed, which provides layer-specific failure data of ILT tissue under static and pulsatile mechanical loads. Methods In total, 112 bone-shaped test specimens are prepared from luminal, medial, and abluminal layers of eight ILTs harvested during open elective AAA repair. Three different types of mechanical experiments, denoted as control test, ultimate strength test, and fatigue test were performed in Dulbecco's modified eagle's medium (DMEM) supplemented with fetal calf serum, L-ascorbic acid, and antibiotics at 37°C and pH 7.0. In detail, fatigue tests, which are experiments, where the ILT tissue is loaded in pulsatile manner, were carried out at three different load levels with a natural frequency of 1.0 Hz. Results ILT's ultimate strength (156.5 kPa, 92.0 kPa, and 47.7 kPa for luminal, medial, and abluminal layers, respectively) and referential stiffness (62.88 kPa, 47.52 kPa, and 41.52 kPa, for luminal, medial, and abluminal layers, respectively) continuously decrease from the inside to the outside. ILT tissue failed within less than 1 hour under pulsatile loading at a load level of 60% ultimate strength, while a load level of about 40% ultimate strength did not cause failure within 13.9 hours. Conclusions ILT tissue is vulnerable against fatigue failure and shows significant decreasing strength with respect to the number of load cycles. Hence, after a reasonable time of pulsating loading ILT's strength is far below its ultimate strength, and when compared with stress predictions from finite element (FE) studies, this indicates the likelihood of fatigue failure in vivo. Failure within the ILT could propagate towards the weakened vessel wall behind it and could initialize AAA failure thereafter.