Abdominal Aortic Aneurysm


Defined as a 50% increase in the diameter compared with the normal adjacent aorta.

Refers to an aortic diameter greater than 3.0 cm.

Estimated prevalence of 1.4% among people between ages 50 and 84 years, or 1.1 million adults.

Prevalence is lower among women then among men and lower among black and Asian persons then among white persons.

114,000 new cases diagnosed each year.

AAAs are identified incidentally on abdominal CT scans, MRIs, ultrasounds performed for an alternative indication at a rate of about 1% of imaging studies.

It is one of the top 15 causes of mortality in the US.
The lack of adequate surveillance when an abdominal aortic aneurysm is noted is associated with an increased risk of rupture and death.

Prevalence is 8.8% in adults over the age of 65 years

A progressive, life-threatening vascular disorder that affects up to 3.3% of older adults.
Large aneurysms are at high risk of rupture, with more than 30% case fatality among those who present to a hospital.

Present in 4-9% of men older than 65 years.

Most patients are asymptomatic, but rupture is associated with an estimated mortality of 65-85%.

Its primary danger is the risk of rupture and death from hemorrhage.

Asymptomatic small aneurysms are detectable by non-invasive screening tests and treatable with endovascular stenting or open surgery.

The goal of management is to repair the aneurysm before ruptured.

The single most important predictor of rupture is the diameter of the aneurysm, with the risk increasing with larger aneurysms.

In a prospective observational study of AAA in patients not considered to be suitable surgical candidate, the risk of rupture was 1% per year among men with an aneurysm of 5 to 5.9 cm in diameter and 14.1% per year in men with an aneurysm measuring 6 cm or more; the respective rates in women were 3.9 and 22.3% per year.

The risk of rupture is less than 0.5% per annum for aneurysms in the range of 3 to 5.4 cm.

A study of patients with abdominal aortic aneurysm, the mortality ranged from 4.2% for elective cases of aneurysm repair, to 16.7% for acute cases, to 55.8% for ruptured cases (Campbell W).

Prevalence is 3 to 10% in individuals older than 50 years.

Prevalence increasing, particularly among older men.

In 2009 in United States there was 6500 AAA-related deaths (CDC).

Recent evidence suggests a reduction in prevalence due to decreased smoking and myocardial infarction incidence.

Men are five times more likely than women to have an AAA.

Prevalence in men is 3-10% compared with only 1 to 2% for women.

Smokers are more likely than former smokers and in turn, are more likely than never smokers to have an AAA.

Years of smoking is more important than the absolute number of cigarettes smoked in the risk of developing an AAA.

The incidence is increase for men who have ever smoke more than 100 cigarettes.

A rare event, under the age of 50 years and incidence increases with age.

The development of AAA occurs in women approximately 10 years later than men.

Risk factors include hypertension, and white race, advanced age,  male sex, family history, ethnicity, history of tobacco use, hypercholesterolemia, hyperglycemia,  and physical inactivity.

Diabetics have half the risk of developing an AAA and suggest a protective effect.

Ultrasound has nearly 100% sensitivity in detecting the presence of an abdominal aortic aneurysm.

Screening with abdominal ultrasound reduces abdominal aortic aneurysm mortality, but not all cause mortality, and is cost-effective among male current and former smokers.

United States Service Task Force recommends that all men age 65-75 with a history of smoking receiving a one time ultrasound screening for AAA.

A 10 year randomized controlled study of ultrasound screening in the UK reduced ruptured aneurysm related deaths from 0.87% to 0.46% (Thompson SG et al).

Initial randomized screening studies showed that screening with abdominal ultrasound reduces AAA related mortality, but not all cause mortality and was thought to be cost-effective among male current and former smokers.

Randomized trials show no survival advantage with surgery over close surveillance for abdominal aortic aneurysm measuring less than 5.5 cm, suggest that this diameter is an appropriate threshold for repair, and that surveillance for aneurysms of less diameter than 5.5 cm is safe and cost-effective.

SAAAVE (Screening Abdominal Aortic Aneurysms Very Efficiently Act) trial showed screening impact to be modest and did not result in changes in rates of abdominal aortic aneurysm repair, rupture, or all- cause mortality (Shreibati JB et al).

Screening is recommended by the US Preventative Services Task Force for men age 65-74 years who have ever smoked.

Usually located in the infrarenal portion of the vessel.

Conventionally, measures more than 3 cm. in diameter.

Primary complication is rupture which leads to 15,000 deaths per year making it the 13th leading cause of death in the U.S.

Tend to remain asymptomatic until the time of rupture.

Risk of rupture is four times higher for women compared to men, and the differences in anatomy, structure, sex related steroids and smoking habits have been suggested to play a role in the increased risk.

2 to 5% of patients present with distal embolization due to thrombus in the AAA sac.

Emboli may cause impaired pedal pulses and toe cyanosis.

Ruptured AAA results in severe bowel or back pain that may radiate to the flank or groin.

Hypotension or unresponsiveness may be the only signs or symptoms in patients with and AAA rupture.

A Swedish autopsy study discovered that 30 to 50% of patients with ruptured abnormal aortic aneurysms die before reaching the hospital (Bengtsson H).

30-40% of patients who reach the hospital without operation die.

Survival rate following rupture is only 20% (Heikkinen M et al).

Overall mortality after rupture is 80 to 90% as operative mortality after rupture is 40-50%.

Approximately 300,000 persons die annually without medical care and 4-5% of sudden deaths are caused by a ruptured abdominal aortic aneurysm it is likely that the process is much more common than is known (O’Sullivan JP).

AAA treatment involves either open surgical repair or endovascular aortic aneurysm repair.

During open surgical repair, the aneurysmal segment is replaced with a tubular or bifurcated prosthetic graft.

During endoscopic aortic aneurysm repair the aneurysm is left intact and blood flow is rerouted through catheter based deployment of a stent graft, thereby avoiding the sac and making it a unnecessary to transiently occlude the aorta.

About 80% of repairs are now performed with the use of endoscopic surgery.

Conventional to offer surgery for aneurysms of 5.5-6.0 cm.

Elective open AAA repair associated with a 5% mortality.

Elective endovascular repair operative risk is 2%, but late complications make the long-term outcomes similar to open surgery.

Endovascular repair has an increased rate of late failure leading to rupture and higher rates of reintervention.

Endovascular repair continues to increase in frequency and by 2010 it accounted for 78% of all intact repairs.

Randomized trials comparing endovascular repair with open repair have generally shown a perioperative benefit of endovascular repair over open repair, long-term survival is similar with the two approaches.

Operative mortality is higher for women.

The risk of rupture with a 5 cm aneurysm is about 10% per year.

At around 6.0 cm. the 2-year mortality from rupture is under 50%.

In patients with small AAA, with a diameter of less than 5.5 cm, the risk of rupture is lower than the risk of surgery and management suggests surveillance.

In the majority of small AAA’s growth is slow, but there is substantial variation in growth rates between different individuals.

No optimal schedule is known between surveillance interval ultrasound for small AAAs.

Patients with small AAA measuring 3 to 3.9 cm should be followed with imaging surveillance in the form of the duplex ultrasonography every three years, whereas those with aneurysms measuring 4 to 4.9 cm in diameter should be followed once a year and those with aneurysms that are 5 cm in diameter or larger should be followed every six months.

Statins, beta blockers and other antihypertensive medication has not been shown to reduce growth.

Meta-analysis of the surveillance intervals for small abdominal aortic aneurysms reveals that several years may be a clinically acceptable interval for the majority of patients with small abdominal aortic aneurysms (RESCAN Collaborators).

In the above analyses the time taken for an AAA of 4 cm or less to have a 10% chance of growing to 5.5 cm is at least three years, And for men with an AAA of 4 cm a smaller it takes more than 3.5 years to have a risk of rupture greater than 1%.

The RESCAN Collaborators suggest that intervals for screening with patients with abdominal aortic aneurysms of a diameter of 3.0-3.9 cm should be 3 years, , 2 years for 4.0-4.4 cm, and yearly for 4.5-5.4 cm and the risk of rupture will be maintained at less than 1%.

Approximately 33,000 patients undergo repair each year.

Surgery is performed on larger aneurysms of 6 cm in diameter or greater, whereas very small aneurysms less than 4 cm in diameter, in which the risk of rupture is low are monitored for growth with ultrasound.

Small AAA’s of 4-5.4 cm, the risk of ruptures is uncertain and management has been debatable.

Frequently occurs in patients with atherosclerosis and the two processes have common risk factors.

Media and adventitious predominantly involved, while in atherosclerosis the lesions are predominantly intimal.

Hallmark finding sin atherosclerosis is foam-cell formation, while in aneurysms there is intense oxidative stress, inflammation smooth muscle apoptosis and matrix degeneration (Miller FJ).

Matrix metalloproteinases mediate elastin and collagen degradation in the aortic wall and matrix metalloproteinases-9 levels are elevated in patients with abdominal aortic aneurysms.

Postoperative death rates from open aneurysm repair range from 0%-4% for single-center reports to approximately 7% for population-based reports.

Surgical death and complication rate increases with advancing age with a death rate of 2.2% for patients in the sixth decade of life to 7.3% for octogenarians.

In patients being observed serial ultrasound should be obtained every 6 to 12 months.

Rapid expansion or growth to 5 cm should trigger surgical management.

For patients turned down for open repair the 3-year survival rate is 17% with more than 50% of patients dying of a ruptured aneurysm.

Endoluminal graft repair reduces complication rate by 70% compared to conventional open repair.

Endovascular aneyrysm repairs estimated to be 70%-80% of repairs rather than open aneurysm techniques.

About 60% of patients with abdominal aortic aneurysms are eligible for endovascular stent graft repair.

In more than 95% of procedures for Endovascular Aortic Aneurysm Repair, a successful implant of an aortic stent is possible.

In a randomized trial of open versus endovascular surgical abdominal aortic aneurysm repair, 30 day operative mortality was 4.3% in participants assigned to conventional open surgery versus 1.8% in those assigned to endovascular treatment.

Randomized controlled studies comparing open aneurysm repair with endovascular aneurysm repair(EVAR) found a reduction in 30 day AAA mortality with EVAR from 0.5-1.8% compared to to 3-4.3% for open repair (Lederle FA et al, Greenhalgh RM et al), with no difference in AAA associated mortality at 2-5 years.

Recovery is faster in patients who undergo EVAR with a median length of hospital stay of two days versus seven days with open surgical repair.

In a study of 44,000 patients who underwent abdomin aortic aneurysm repair the 30 day mortality was 1.2% after EVAR and 4.8% after open surgical repair.

Re-interventions related to repair are more frequent among patients who undergo EVAR.

Surgical wound related complication such as incision hernias or bowel obstructions and more likely among patients who undergo open repair.


A normal ultrasound scan at age 65 years effectively rules out the risk of clinically significant aneurysm disease for life in men.

In patients  with small abdominal aortic aneurysms exercise and training are not associate with the adverse events or influence the growth rates of small abdominal aortic aneurysms.

National average mortality rate 3.9%.

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