Majority Of Abdominal Aortic Aneurysms Research Articles

Abdominal aortic aneurysms part one: Epidemiology, presentation and preoperative considerations.

An abdominal aortic aneurysm is an irreversible dilatation of the abdominal aorta. The majority of abdominal aortic aneurysms are asymptomatic and identified incidentally while investigating a separate pathology. Others are detected by national screening programmes and some present due to a growth or rupture. Symptomatic or ruptured aneurysms require urgent or emergency repair in patients fit for surgery. Perioperative practitioners should therefore be aware of how patients with abdominal aortic aneurysms present and are investigated, so that they can implement timely management. Guidelines have been recently updated to reflect this. This literature review discusses these recommendations and explores the evidence upon which they are based. The aim of this article is to highlight the important preoperative principles that need to be considered in cases of abdominal aortic aneurysm.

Abdominal aortic aneurysm screening programme

This is the second article in a series of articles regarding screening programmes. In this article, an overview of the abdominal aorta is provided. The article also considers the abdominal aortic aneurysm screening programme. Aortic abdominal aneurysm is described. The majority of abdominal aortic aneurysms are asymptomatic; however, if there are any symptoms, these are explained. All four UK countries offer men aged 65 years and over a screening opportunity using an ultrasound scan, the fundamental aspects of abdominal aortic aneurysm screening programmes is offered. It is emphasised that screening is not mandatory in the UK; the man has a right to decline the invitation to attend any screening programme.

On the Relative Impact of Intraluminal Thrombus Heterogeneity on Abdominal Aortic Aneurysm Mechanics.

Intraluminal thrombus (ILT) is present in the majority of abdominal aortic aneurysms (AAA) of a size warranting consideration for surgical or endovascular intervention. The rupture risk of AAAs is thought to be related to the balance of vessel wall strength and the mechanical stress caused by systemic blood pressure. Previous finite element analyses of AAAs have shown that ILT can reduce and homogenize aneurysm wall stress. These works have largely considered ILT to be homogeneous in mechanical character or have idealized a stiffness distribution through the thrombus thickness. In this work, we use magnetic resonance imaging (MRI) to delineate the heterogeneous composition of ILT in 7 AAAs and perform patient-specific finite element analysis under multiple conditions of ILT layer stiffness disparity. We find that explicit incorporation of ILT heterogeneity in the finite element analysis is unlikely to substantially alter major stress analysis predictions regarding aneurysm rupture risk in comparison to models assuming a homogenous thrombus, provided that the maximal ILT stiffness is the same between models. Our results also show that under a homogeneous ILT assumption, the choice of ILT stiffness from values common in the literature can result in significantly larger variations in stress predictions compared to the effects of thrombus heterogeneity.

Effect of intraluminal thrombus on growth rate of abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) includes a variety of morphologies with changing properties. Growth rate is one of the most important factors directly linked to the risk of rupture. Intraluminal thrombus (ILT) covering aortic wall is found in the majority of AAAs. Yet, its role in biomechanical processes in AAA remains unclear. From one point of view ILT can serve as protective factor in reducing wall stress of AAA and thus slow down the growth. Modern concept of multilayered ILT proved active inflammatory processes inside, that can significantly affect the quality of the wall and thus lead to a higher growth rate and higher risk of rupture. The goal of this study was to analyze the effect of ILT on growth rate of AAA and support one of these theories. Retrospective study of computed tomography angiography scans of AAA of 26 patients was performed. Forty pairs of consecutive scans have been analyzed. Periods between two scans varied. Maximal infrarenal diameter of AAA and size of ILT were measured. AAAs were split into 4 groups according to their initial diameter. Growth rate was calculated for each AAA and linked to the relative size of ILT. These values were statistically evaluated. Negative correlation between relative size of ILT and growth rate was found (P=0.042062). This significant result proved that thicker thrombus slowed down the growth of AAA and vice versa, smaller relative size of ILT was linked to higher growth rate. This finding shows importance of ILT as one of the key factors influencing biomechanical processes inside an AAA. Results of this study may contribute to future researches of this topic.

Epidemiology and contemporary management of abdominal aortic aneurysms.

Abdominal aortic aneurysm (AAA) is most commonly defined as a maximal diameter of the abdominal aorta in excess of 3 cm in either anterior-posterior or transverse planes or, alternatively, as a focal dilation ≥1.5 times the diameter of the normal adjacent arterial segment. Risk factors for the development of AAA include age >60, tobacco use, male gender, Caucasian race, and family history of AAA. Aneurysm growth and rupture risk appear to be associated with persistent tobacco use, female gender, and chronic pulmonary disease. The majority of AAAs are asymptomatic and detected incidentally on various imaging studies, including abdominal ultrasound, and computed tomographic angiography. Symptoms associated with AAA may include abdominal or back pain, thromboembolization, atheroembolization, aortic rupture, or development of an arteriovenous or aortoenteric fistula. The Screening Abdominal Aortic Aneurysms Efficiently (SAAAVE) Act provides coverage for a one-time screening abdominal ultrasound at age 65 for men who have smoked at least 100 cigarettes and women who have family history of AAA disease. Medical management is recommended for asymptomatic patients with AAAs <5 cm in diameter and focuses on modifiable risk factors, including smoking cessation and blood pressure control. Primary indications for intervention in patients with AAA include development of symptoms, rupture, rapid aneurysm growth (>5 mm/6 months), or presence of a fusiform aneurysm with maximum diameter of 5.5 cm or greater. Intervention for AAA includes conventional open surgical repair and endovascular aortic stent graft repair.

The Consequences of Real Life Practice of Early Abdominal Aortic Aneurysm Repair: A Cost-Benefit Analysis

The reported 54mm median intervention diameter for endovascular aneurysm repair (EVAR) in the Vascular Quality Initiative and European data from the Pharmaceutical Aneurysm Stabilisation Trial (PHAST) implies that in real life the majority of abdominal aortic aneurysm (AAA) repairs occur at diameters smaller than the consensus intervention threshold of 55mm. This study explores the potential consequences of this practice. The differences between real life AAA repair and consensus based intervention threshold were explored in reported data from vascular quality initiatives and PHAST. The subsequent consequences of advancement of endovascular aneurysm repair (EVAR) were estimated using a multistate model based on life tables for the EVAR Medicare population. There appears an approximate 5mm difference in AAA diameter between real life practice and consensus intervention threshold. Assuming a 2.5mm annual growth rate, this results in an approximately 2 year advancement of AAA repair. According to the model used, early repair reduces overall small aneurysm patient mortality by 2.3%, it results in 21.9% more EVAR procedures, more EVAR related deaths, and 42.3% and 36.8% more open and endovascular re-interventions, respectively. Cost-benefit estimates imply 482 fewer AAA related deaths, but 140 extra EVAR related deaths for a population of more than 30,000 AAA patients, and a 300 million USD increase in health costs for the 8 year observation period in the Medicare population. In the real life situation a large proportion of EVAR procedures appear to occur before reaching the consensus threshold. Although this reduces mortality, it comes at a cost of approximately 1 million USD per prevented rupture related death.

Inhibition of early AAA formation by aortic intraluminal pentagalloyl glucose (PGG) infusion in a novel porcine AAA model

BackgroundThe vast majority of abdominal aortic aneurysms found in screening programs are small, and as no effective treatment exits, many will expand until surgery is indicated. Therefore, it remains intriguing to develop a safe and low cost treatment of these small aneurysms, that is able to prevent or delay their expansion.In this study, we investigated whether intraluminal delivered pentagalloyl glucose (PGG) can impair the early AAA development in a porcine model.MethodsThe infrarenal aorta was exposed in thirty pigs. Twenty underwent an elastase based AAA inducing procedure and ten of these received an additional intraluminal PGG infusion. The final 10 were sham operated and served as controls.ResultsAll pigs who only had an elastase infusion developed macroscopically expanding AAAs. In pigs treated with an additional PGG infusion the growth rate of the AP-diameter rapidly returned to physiological values as seen in the control group. In the elastase group, histology revealed more or less complete resolution of the elastic lamellae in the media while they were more abundant, coherent and structurally organized in the PGG group. The control group displayed normal physiological growth and histology.ConclusionIn our model, intraluminal delivered PGG is able to penetrate the aortic wall from the inside and impair the early AAA development by stabilizing the elastic lamellae and preserving their integrity. The principle holds a high clinical potential if it can be translated to human conditions, since it, if so, potentially could represent a new drug for stabilizing small abdominal aneurysms.

Gigantic 25-cm abdominal aortic aneurysm

A 69-year-old man presented to the hospital in June 1993 with a prominent, visibly pulsatile abdominal mass (A). The patient had a history of smoking, hypertension, hepatitis C, and tuberculosis and had noted a pulsation in his abdomen for several years but had never sought medical attention. Physical examination demonstrated a very large, nontender, pulsatile mass with a soft bruit. Translumbar aortography revealed a gigantic infrarenal abdominal aortic aneurysm (AAA) measuring 25 cm in diameter with a large mural thrombus extending to the aortic bifurcation and both common iliac arteries (B). The patient was prepared for urgent open surgical aneurysm repair under general anesthesia and gave informed consent for photographic documentation and publication of his case. At operation (C), the aneurysm was readily exposed; the transverse diameter was measured with a centimeter scale and recorded as 25 cm by the surgeon. After infrarenal cross-clamping, the aneurysm was opened, a massive mural thrombus was removed, and a bifurcated 22 10-cm knitted Dacron aortoiliac graft was sewn in place (D). Excess aneurysm wall was trimmed, and the remaining aneurysm wall was closed over the graft. The patient received one unit of Cell Saver blood transfusion, was extubated immediately after the operation, and had an uneventful recovery. He was discharged from the hospital on day 12 and had no subsequent events related to the aneurysm or surgical repair. He survived for 7 years, dying of heart failure at the age of 76 years. The majority of AAAs are discovered when they are 6 cm, with an annual rupture risk of 30% to 50% for aneurysms >8 cm. Thus, it is unlikely that patients with very large aneurysms survive for a long time. Indeed, aneurysms >10 cm are rare, with only a few reports of successful repair of giant aneurysms larger than 12 cm. The largest reported diameter in published cases of giant unruptured AAA is 15 cm. This report of a 25-cm gigantic AAA may represent the largest successfully repaired infrarenal AAA in the world’s literature.

PS26. Vascular Surgeons Repair an Increasing Majority of Abdominal Aortic Aneurysms after the Introduction of EVAR

PS26. Vascular Surgeons Repair an Increasing Majority of Abdominal Aortic Aneurysms after the Introduction of EVAR

Abstract 253: Abdominal Aortic Aneurysms: Protein Targets for Autoimmunity

Objectives: The vast majority of Abdominal Aortic Aneurysm (AAA) patients have a history of smoking. The current hypothesis is that smoking induces post-translational protein modifications within the abdominal aorta resulting in site-specific antigenic targets for humoral immunity, and leads to a complex inflammatory milieu that ultimately gives rise to mature AAAs. Methods: Plasma samples from patients with AAAs were separated by smoking status (Non-smoker = NS [n = 5]; Smoker = S [n = 15]; Prior Smoker = PS [n = 36]). Aortic wall was harvested from AAA (n = 5) and healthy control aorta (n = 5). Membrane proteins were extracted from AAA aortas by phase separation and bound to affinity columns. Plasma from NS, S, and PS groups was passed through these columns to isolate immunoglobulins (eluted IgGs). Duplicate samples of pooled control aortic tissue proteins underwent electrophoresis for Western blotting and Coomassie staining. Western blots were developed with eluted IgGs from the NS, S, and PS groups as well as IgGs from healthy volunteers as negative control. The Western blots were analyzed for differences in banding patterns between NS and S or PS groups and the corresponding proteins from Coomassie stained gels were excised for Mass Spectrometry (LC-MS/MS analysis). Results: Western blot experiments revealed a ∼38 kD band in NS but no correlating band in S and PS groups, as well as ∼22 kD and ∼33 kD bands present in S and PS but no correlating bands in the NS group. LC-MS/MS analysis of these 3 bands identified the encompassed proteins as having sequence homologies with TROPOMYOSIN 1, TROPOMYOSIN 2, TRANSGELIN, INTEGRIN BETA-1, VERSICAN, PEROXIREDOXIN 2 and OSTEOGLYCIN (Mimecan), and that these proteins differed in relative abundance between the three groups. Conclusions: We identified putative proteins in normal human aortas that could represent autoimmune targets leading to AAA development. The discrepancy between the molecular weights of putative targets and the bands used for LC-MS/MS analysis possibly reflects post-translational processing of the larger parent protein resulting in auto-antigenicity.

Effects of Age on the Elastic Properties of the Intraluminal Thrombus and the Thrombus-covered Wall in Abdominal Aortic Aneurysms: Biaxial Extension Behaviour and Material Modelling

Objective The intraluminal thrombus (ILT) present in the majority of abdominal aortic aneurysms (AAAs) plays an important role in aneurysm wall weakening. Studying the age-dependent elastic properties of the ILT and the thrombus-covered wall provides a better understanding of the potential effect of ILT on AAA remodelling. Materials and methods A total of 43 AAA samples (mean age 67 ± 6 years) including ILT and AAA wall was harvested. Biaxial extension tests on the three individual ILT layers and the thrombus-covered wall were performed. Histological investigations of the thrombi were performed to determine four different age phases, and to correlate with the change in the mechanical properties. A three-dimensional material model was fitted to the experimental data. Results The luminal layers of the ILT exhibit anisotropic stress responses, whereas the medial and the abluminal layers are isotropic materials. The stresses at failure in the equibiaxial protocol continuously decrease from the luminal to the abluminal side, whereby cracks, mainly oriented along the longitudinal direction, can be observed in the ruptured luminal layers. The thrombi in the third and fourth phases contribute to wall weakening and to an increase of the mechanical anisotropy of their covered walls. The material models for the thrombi and the thrombus-covered walls are in excellent agreement with the experimental data. Conclusion Our results suggest that thrombus age might be a potential predictor for the strength of the wall underneath the ILT and AAA rupture.

Occlusion of Inferior Vena Cava: A Singular Presentation of Abdominal Aortic Aneurysm

Even though the majority of abdominal aortic aneurysm s(AAAs) are asymptomatic, they can occasionally manifest as a result of adjacent structures involvement. Although the most frequent venous complication of AAA is rupture into the inferior vena cava (IVC), venous compression can infrequently occur. The authors report a particularly rare case of compression and thrombosis of the IVC by AAA. Patient was treated by preoperative placement of an IVC filter to impede pulmonary embolism and subsequently by open surgical repair. Besides discussing the circumstances associated with IVC compression by AAA, the authors also discuss the treatment strategy adopted and the possible alternatives.

Compressive mechanical properties of the intraluminal thrombus in abdominal aortic aneurysms and fibrin-based thrombus mimics

An intraluminal thrombus (ILT) forms in the majority of abdominal aortic aneurysms (AAAs). While the ILT has traditionally been perceived as a byproduct of aneurysmal disease, the mechanical environment within the ILT may contribute to the degeneration of the aortic wall by affecting biological events of cells embedded within the ILT. In this study, the drained secant modulus ( E 5∼modulus at 5% strain) of ILT specimens (luminal, medial, and abluminal) procured from elective open repair was measured and compared using unconfined compression. Five groups of fibrin-based thrombus mimics were also synthesized by mixing various combinations of fibrinogen, thrombin, and calcium. Drained secant moduli were compared to determine the effect of the components’ concentrations on mimic stiffness. The stiffness of mimics was also compared to the native ILT. Preliminary data on the water content of the ILT layers and mimics was measured. It was found that the abluminal layer ( E 5=19.3 kPa) is stiffer than the medial (2.49 kPa) and luminal (1.54 kPa) layers, both of which are statistically similar. E 5 of the mimics (0.63, 0.22, 0.23, 0.87, and 2.54 kPa) is dependent on the concentration of all three components: E 5 decreases with a decrease in fibrinogen (60–20 and 20–15 mg/ml) and a decrease in thrombin (3–0.3 units/ml), and E 5 increases with a decrease in calcium (0.1–0.01 M). E 5 from two of the mimics were not statistically different than the medial and luminal layers of ILT. A thrombus mimic with similar biochemical components, structure, and mechanical properties as native ILT would provide an appropriate test medium for AAA mechanobiology studies.

Guidelines for Noninvasive Vascular Laboratory Testing: A Report from the American Society of Echocardiography and the Society of Vascular Medicine and Biology

Accompanying the rapid growth of interest inpercutaneous vascular interventions, there hasbeen increasing interest among cardiologists inperforming noninvasive vascular testing using ul-trasound. In an attempt to provide recommenda-tions on the best practices in vascular laboratorytesting, this report has been prepared by a writinggroup from the American Society of Echocardiog-raphy (ASE) and the Society of Vascular Medicineand Biology. The document summarizes principlesintegral to vascular duplex ultrasound–includingcolor Doppler, spectral Doppler waveform analy-sis, power Doppler, and the use of contrast.Appropriate indications and interpretation of ca-rotid artery, renal artery, abdominal aorta, andperipheral artery ultrasound imaging are de-scribed. A dedicated section summarizes noninva-sive techniques for physiologic vascular testing ofthe lower extremity arteries–including measure-ment of segmental pressures and pulse volumeplethysmography. The use of exercise testing inthe evaluation of peripheral artery disease, ultra-sound evaluation of the lower extremities afterpercutaneous revascularization, and the diagnosisand management of iatrogenic pseudoaneurysm(PSA) is also discussed. A section on the importanttopic of vascular laboratory accreditation is in-cluded. Finally, additional details regarding propertechnique for performance of the various vasculartests and procedures are included in the Appen-dix.

Surgical management of abdominal aortic aneurysm.

Abdominal aortic aneurysms (AAA) are increasingly common in the aging population. While the etiology of abdominal aortic aneurysms is unknown, there is growing evidence that suggests an immune response. The majority of AAA are asymptomatic and when treated are standard open surgical procedures. The overall mortality rate is 5% or less. The current recommendations for the treatment of aneurysms are based on diameter: diameters exceeding 5 cm in good-risk younger patients should be treated. Aortic aneurysms tend to enlarge over time with a growth-rate between 0.2 and 0.4 mm per year. Once rupture occurs mortality is estimated to exceed 75%, with half of the patients dying prior to arriving at the hospital and the remaining one-half following surgical correction. Recently, minimally invasive techniques have been developed to treat AAA in high-risk patients. These techniques involve the use of covered stented grafts. Current clinical investigations are underway both in this country and in Europe, which have yielded promising results. However, long-term complications are unknown. Currently, aortic aneurysms are best treated with open surgical management.

A Prospective Study of Changes in Morphology and Dimensions of Abdominal Aortic Aneurysms following Endoluminal Repair: A Preliminary Report

Purpose: The aim of this prospective study was to analyze early changes in morphology and dimensions of abdominal aortic aneurysms (AAA) following endoluminal repair. Methods: Forty-two of 62 patients undergoing endoluminal repair of AAAs between May 1992 and November 1994 were potentially available for follow-up at 6 months or longer after operation. After excluding patients with failed endoluminal repairs, patients who died within 6 months of operation, and patients with anastomotic aneurysms, a study group of 30 patients remained. Contrast-enhanced computed tomography (CE-CT) was performed preoperatively, within 10 days of operation, and at 6 and 12 months postprocedure. Based on the postoperative CE-CT findings, patients were divided into two groups: those with no extravasation of contrast into the aneurysmal sac (group I; n = 26), and those in which there was contrast extravasation (“leak”) into the aneurysmal sac (group II; n = 4). Results: The mean maximum diameters of AAAs in group I diminished progressively at 6 and 12 months, while those in group II increased. Twenty-three (88%) patients in group I had decreased diameter of AAA, while all patients in group II had progressive increase in AAA diameter. Patients who had an increase in AAA diameter had a significantly higher incidence of leak compared with those who had a decrease in diameter (p = 0.001). Conclusions: The majority of AAAs in which the sac has been excluded from the general circulation diminish in size following successful endoluminal repair. An increase in size occurs in those AAAs in which a communication exists between the aortic lumen and the sac. These results suggest that successfully excluded AAAs that continue to increase in size should be suspected of having an undetected leak.

Is screening once at age 65 an effective method for detection of abdominal aortic aneurysms?

To evaluate whether a single screening at 65 or screening at 65 and 70 are the methods of choice to detect the majority of abdominal aortic aneurysms (AAA) suitable for treatment. District general hospital, district general practice and community. Data were collated from four studies (a pilot, a control trial, and two cohorts) of abdominal ultrasound screening of an invited group of 11 666 men and women aged 65-80 to derive age related prevalence, invitation acceptance rates, and operative mortality. Deaths from AAA rupture were obtained from district registrars' returns. The prevalence of AAA increased with age being greater overall in men (6.8%) than in women (1.2%). From ages 65 to 80 the prevalence in men increased from 5.4% to 10.4%, and in women from 0.6% to 2.1%. In men and women 4% of patients dying from AAA rupture were aged 65 or under and 85% of deaths occurred over the age of 70. Acceptance rates for screening decreased between 65 and 80 from 80.5% to 66.2% in men and from 72.7% to 58.3% in women. In elective or symptomatic patients operative mortality was zero up to the age of 70, increasing to 7.1% in older patients. Men should be screened at age 65 to obtain a high acceptance rate and to identify those with AAA most likely to benefit from treatment. The prevalence is relatively low at this age so an additional screen at age 70 is recommended, which would pick up a further 3.7% of patients with AAA, at which age intervention is likely to be of benefit.