Mount Carmel Health Partners Clinical Guidelines Abdominal Aortic Aneurysm | Page 2

Incidence, Mortality, and Risk Factors
Abdominal aortic aneurysms (AAA) continue to be a significant medical and surgical problem with a high associated mortality rate. AAAs
affect 4% to 9% of individuals over the age of 60, with a predilection for men between 65 and 79 years of age. The incidence of AAA is
increasing as the population ages, with approximately 15,000 people dying from AAA each year in the United States (8,700 of these
deaths occur from acute rupture). Abdominal aortic aneurysm is the tenth leading cause of death of older men in the United States and
is responsible for 0.8% of all deaths. The mortality rate associated with elective operative repair is 2% to 6%, and there is a significant
risk of major complications; higher complication rates are associated with emergent repair. The dreaded complication of an AAA is
aortic rupture, which has a death rate of 80% for all patients reaching the hospital alive. The mortality rate is 50% for those patients able
to undergo the emergent surgery necessary for vessel repair.
An arterial aneurysm is defined as a permanent localized enlargement of an artery to more than 1.5 times its expected diameter. The
normal abdominal aorta is 2 cm or less in diameter, and thus an abdominal aortic aneurysm is present once the aorta dilates to a
diameter of 3 cm or more.
Hypertension, diabetes, and hyperlipidemia contribute to atherosclerosis, which has traditionally been taught as the most significant
risk factor for developing an AAA. Recent studies, however, have shown that genetics are more indicative of risk.
Ruptured abdominal aortic aneurysms are a highly lethal vascular emergency. Mortality from an out-of-hospital rupture is over 60%,
while patients who survive to hospital arrival have an operative mortality rate of approximately 41 - 50%. In contrast, patients
undergoing elective repair have mortality rates of only 5 - 10% (see Table Two below).
Current smokers are 7.6 times more likely to have an AAA than nonsmokers. The prevalence of AAAs among first-degree relatives of
patients with an AAA is 15 - 29%, compared to 2% among relatives of controls.
In general, the larger the aneurysm, the greater the risk of rupture. Additional risk factors for rupture include hypertension, underlying
chronic obstructive pulmonary disease (COPD), a diameter exceeding 6 cm in men and 5 cm in women, local outpouchings, termed
“blebs” or “blisters” of the aneurysm wall, eccentric or saccular aneurysms, rapid AAA expansion >1 cm per year, a familial history of
AAAs in other first-degree relatives, and an increase in diameter over 5 mm in any 6-month period (regardless of initial or baseline
size).
Retroperitoneal AAA rupture is more likely to be seen in patients arriving at hospitals alive, while intraperitoneal rupture is usually
rapidly fatal.
A review of the patient’s medical history for risk factors for AAA should include identification of those who have undergone previous
surgical AAA grafting or endoluminal stent-graft repair. These patients are at particularly high risk for AAA rupture and face long-term
complications, including graft infection, thrombosis, anastomotic aneurysm, dissection, and development of aortoenteric fistulas.
Patients with a history of surgical or endovascular repair suffering complications will usually present in similar fashion with complaints of
pain and fever.

Table One: Risk Factors for AAA

Table Two: Risk Factors for Aneurysm Rupture
Risk Factors for AAA Rupture

Risk Factors For Abdominal Aortic Aneurysm
• Hypertension

• Hypertension

• Smoking

• Underlying chronic obstructive pulmonary disease (COPD)

• Atherosclerotic disease

• Diameter greater than 6 cm in men and
greater than 5 cm in women

• Turner, Marfan, or Ehlers-Danlos Type IV Syndromes

• Local outpouchings (“blebs” or “blisters”) of the
aneurysm wall

• Familial connective tissue defects
• Male gender

• Eccentric or saccular aneurysms

• Age greater than 50 years

• AAA expansion greater than 1 cm per year

• Inflammatory or infectious aortitis

• Familial history of AAAs in other first-degree relatives

• Known aortic pathology or previous aortic surgery

• Increase in diameter of over 5 mm in any 6-month period

Abdominal Aortic Aneurysm - 2