Diagnosis and Monitoring of Abdominal Aortic Aneurysm: Current Status and Future Prospects

Abstract

Abdominal aortic aneurysm (AAA) remains an important cause of morbidity and mortality in elderly men, and prevalence is predicted to increase in parallel with a global ageing population. AAA is commonly asymptomatic, and in the absence of routine screening, diagnosis is usually incidental when imaging to assess unrelated medical complaints. In the absence of approved diagnostic and prognostic markers, AAAs are monitored conservatively via medical imaging until aortic diameter approaches 50-55mm and surgical repair is performed. There is currently significant interest in identifying molecular markers of diagnostic and prognostic value for AAA. Here we outline the current guidelines for AAA management, and discuss modern scientific techniques currently employed to identify improved diagnostic and prognostic markers. KeywordsAbdominal aortic aneurysm; diagnosis; prognosis; biomarker INTRODUCTIONAn abdominal aortic aneurysm (AAA) is a dilation of the infra-renal aorta, which appears to result from chronic weakening of the arterial wall, increasing the risk of fatal rupture.1 -3 AAA is also associated with an increased risk of other major cardiovascular events in aneurysmal patients. For example the UK small aneurysm trial (UKSAT), demonstrated that only 16% of deaths in patients with 40-55mm AAAs was related to AAA repair or rupture while ~50% were due to other cardiovascular causes (mainly myocardial infarction and stroke).4 Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access AAA pathologyMacroscopically, an AAA can be considered a dilatation of the infrarenal aorta, giving rise to a permanent vessel diameter >30mm (typical abdominal aortic diameter ranges from 15 to 25mm). 23-27 AAA vessel dilation is commonly progressive, and is often accompanied by the formation of a laminated, non-occlusive, intraluminal thrombus.28 -29 Thrombus size and location varies between patients, and the arterial wall may be partially or completely covered by the thrombus ( Figure 1A and B). 30 The thrombus remains in permanent contact with circulating blood and is continually remodeled, 31,32 and thrombus size increases in parallel with aortic dilation. Due to constant remodeling the thrombus is a laminated structure comprising a red blood cell-rich luminal layer in contact with the flowing blood, progressing to a brown fibrinolysed layer at the aortic wall. 29 Localised hypoxia has been demonstrated in regions of the aorta covered by the thrombus and this has been suggested to contribute to physiological stresses within the arterial wall. 33 Similar to other vascular dise...

VPO1 Modulates Vascular Smooth Muscle Cell Phenotypic Switch by Activating Extracellular Signal‐regulated Kinase 1/2 (ERK 1/2) in Abdominal Aortic Aneurysms

“…During the early stages of AAA formation, VSMC undergo phenotypic switch which is characterized by downregulation of VSMC differentiation markers, such as SM‐22α, α‐SMA as well as an increase in proliferation, migration, and synthesis of extracellular matrix proteins 2, 26. In our study, we observed decreased levels of α‐SMA and SM‐22α by immunohistochemistry in human AAA and PPE‐induced AAA tissues.…”

Abdominal Aortic Aneurysm in Patients with Coronary Artery Disease: A Review Article

“…On the contrary, an elective AAA repair, recommended in most patients with an abdominal aortic diameter exceeding 50-55 mm or rapid growth (> 1 cm/y), is associated with a mortality risk of 2% to 6% (Kurvers at al., 2003;Sakalihasan et al, 2005). Health organizations recently recommended one-time screening for AAA by ultrasonography for men aged between 65 and 75 years with a smoking history, thereby reducing AAA related mortality rates by 50% (Cosford & Leng, 2007;Ehlers et al, 2008;Ferket et al, 2011;Moxon et al, 2010;Takagi et al, 2010). However, they advised against screening in men below 65 and over 75 years, and in women, since the number of AAArelated deaths that can be prevented by screening these populations is too small.…”

Ultrasound in Abdominal Aortic Aneurysm

“…Due to current investigation of markers associated with AAA, targeted ultrasound imaging may be a future option (Moxon et al, 2010;Villanueva 2008). With increased knowledge of pathophysiological mechanisms, pharmacotherapy or gene therapy may be available for stabilization of aneurysms (Baxter et al, 2008;Cooper et al, 2009;Golledge et al, 2009;Raffetto & Khalil, 2008;Twine & Williams, 2011).…”