Biomechanical Determinants of Abdominal Aortic Aneurysm Rupture

Abstract

Abstract-Rupture of abdominal aortic aneurysm (AAA) represents a significant clinical event, having a mortality rate of 90% and being currently ranked as the 13th leading cause of death in the US. The ability to reliably evaluate the susceptibility of a particular AAA to rupture on a case-specific basis could vastly improve the clinical management of these patients. Because AAA rupture represents a mechanical failure of the degenerated aortic wall, biomechanical considerations are important to understand this process and to improve our predictions of its occurrence. Presented here is an overview of research to date related to the biomechanics of AAA rupture. This includes a summary of results related to ex vivo and in vivo mechanical testing, noninvasive AAA wall stress estimations, and potential mechanisms of AAA wall weakening. We conclude with a demonstration of a biomechanics-based approach to predicting AAA rupture on a patient-specific basis, which may ultimately prove to be superior to the widely and currently used maximum diameter criterion. Key Words: abdominal aortic aneurysm Ⅲ biomechanics Ⅲ rupture Ⅲ strength Ⅲ stress A bdominal aortic aneurysm (AAA) is a focal enlargement of the infrarenal aorta, which occurs over a time course of several years. This condition is present in Ϸ2% of the elderly population, with Ϸ150 000 new cases diagnosed each year, and the incidence is increasing. 1,2 If left untreated, AAA will gradually expand until rupture; it is an event that carries a mortality rate of 90% and that is ranked as the 13th most common cause of death in the US. 3 Current AAA repair procedures are expensive and carry significant morbidity and mortality risks.Open repair of AAA is a major surgical procedure that requires patients to be hospitalized typically for 1 week and to recuperate at home for several more weeks. The mean postoperative mortality for elective repair is Ϸ5% and for emergency operations 47% (range 27% to 69%). 4 The major drawback of open repair is the compromised quality of life after surgery because of postoperative pain, the prolonged recovery period, and the high costs associated with both the surgery and the recovery.An alternative approach that avoids the extensive tissue dissection associated with open repair is the minimally invasive endovascular repair procedure. The potential advantages of endovascular AAA repair include reductions in mortality, morbidity, blood loss, hospital stay, intensive careOriginal

Biomechanical properties of the Marfan's aortic root and ascending aorta before and after personalised external aortic root support surgery

“…Figure 8 illustrates regions of stress greater than 290 kPa in the post-PEARS single-layer models for all three patients. Previous studies showed that peak stresses of an aneurysmal aorta were between 290 and 450 kPa [26]. As a conservative comparison to a known reference value, 290 kPa was chosen to highlight the high stress regions.…”

Mechanical behaviour and rupture of normal and pathological human ascending aortic wall

“…The risk of growth and rupture is commonly related to aortic diameter, with this being the most used criterion for intervention [1,7]. Although there is considerable evidence that the risk of rupture, dissection or death is dramatically increased in thoracic aortic aneurysms with diameters in excess of 60 or 70 mm (for ascending or descending aorta, respectively) [3,5], the fraction of aneurysms that rupture before reaching that size is not negligible [4,14,24]. Rupture of aneurysms occurs when the mechanical stresses acting on that zone of the vessel exceed the strength of the wall tissue.…”

Computational Growth and Remodeling of Abdominal Aortic Aneurysms Constrained by the Spine

“…We speculate that the inclusion of bending stiffness in our analysis intensifies the effects of spine contact on the morphology, wall stress distribution, and PWS, beyond what we observed in this study. Accurate measures of wall strength are yet to be considered in our analysis for a reliable assessment of rupture [50,51,57,58]. Our simulation cases represent hypothetical models of AAAs initiated by artificial elastin degradation in a healthy aorta instead of the real elastin loss in a patient's AAA wall.…”