Figure 96-4. CT scan demonstrates a large abdominal aortic aneurysm. Note that the majority of the lumen is filled with contrast.

Figure 96-5. 3D CT of the aorta and the iliac, femoral, and visceral arteries is shown. Note the infrarenal abdominal aortic

aneurysm that extends to the aortic bifurcation.

Both magnetic resonance imaging (MRI) and catheter-based arteriography have been used as

diagnostic imaging studies for patients with AAAs. The image quality and overall sensitivity of MRI is

comparable to CT, but the technology is not as widely available and most surgeons are less familiar

with interpreting the images. Furthermore, the technique is relatively contraindicated for patients with

ferromagnetic devices (e.g., pacemakers, joints) or renal insufficiency, and imaging critically ill patients

is cumbersome, if not prohibitive.

Importantly, aneurysms are frequently diagnosed during catheter-based arteriography performed for

other purposes, but this should not be viewed as a diagnostic test of choice for AAAs. An arteriogram

only delineates the lumen of the vessels (i.e., aorta, iliac and femoral arteries), and thus gives no

indication of aneurysm extent or diameter. AAAs are often filled with laminated thrombus and may

have a relatively normal appearing lumen. The “lumenogram” produced by the contrast reflects the

patent lumen rather than the “true” lumen of the vessel (and the actual cross-sectional diameter of the

aneurysm).

The diagnostic approach and initial treatment for patients with a potential ruptured aneurysm merit

further comment. Because of the high attendant mortality rate, prompt diagnosis and repair are

necessary. In a study from the Cleveland Clinic Vascular Registry, the operative mortality rate

associated with ruptured AAAs increased from 35% when the initial diagnosis was correct to 75% when

2724

incorrect.99 Admittedly, the clinical presentation may be confusing, and delays in diagnosis are not

uncommon. The classic triad of hypotension, abdominal pain, and a pulsatile abdominal mass was

present in only 50% of patients with ruptured aneurysms in a single institutional series.100

Elderly patients who present to the emergency room in a hemodynamically unstable state with

abdominal or back pain can often be evaluated quickly in the emergency department with ultrasound or

CTA if they are stable enough for the examination. The potential causes of shock (i.e., hypovolemic,

cardiogenic, septic, neurogenic) can usually be quickly differentiated by a brief history and physical

examination. However, this clinical scenario is most suggestive of hypovolemic or hemorrhagic shock

resulting from an intra-abdominal catastrophe. The differential diagnosis is extensive and includes

pancreatitis, mesenteric infarction, acute Addisonian crisis, and rupture of a visceral artery aneurysm in

addition to rupture of an AAA. A myocardial infarction can mimic a ruptured aneurysm in this patient

population and potentially confounds the diagnosis, although it can usually be confirmed by the findings

on electrocardiogram. Additional diagnostic imaging has not traditionally been considered necessary in

this setting and, indeed, has been considered potentially harmful due to the obligatory delay in getting

patients to the operating room. Due to the dramatic reduction in CT acquisition times and the potential

feasibility of endovascular repair, abdominal/pelvic CT scans are allowable in this scenario to confirm

the diagnosis and plan the operative procedure, provided it can be performed expeditiously. This

approach has the added advantage of reducing the number of negative abdominal explorations in

critically ill patients. A natural history study of patients with ruptured AAAs not offered operative repair

reported that <15% of the patients died within 2 hours of hospital admission.101 Based upon these

findings, the authors concluded that most patients with ruptured aneurysms are sufficiently stable to

undergo a CT scan and this opinion has been supported by improved mortality results of EVAR for

ruptured aneurysms.89

Several findings on CT are suggestive of a ruptured AAA including disruption of the calcium ring

within the aortic wall, disruption of the aortic margins, retroperitoneal hematomas, mass lesions in the

psoas region, displacement of the kidneys, abnormal soft tissues posterior to the aorta, effacement of

the normal fat planes between the aorta and adjacent viscera, and abnormal retroperitoneal fluid

collections (Fig. 96-6). Patients undergoing an emergent CT arteriogram to rule out a ruptured AAA

should not receive oral contrast because of the delay associated with its administration and the

confounding effects on the imaging of the vessels.

Figure 96-6. Contrast CT demonstrates a ruptured abdominal aortic aneurysm. Note the large retroperitoneal hematoma and the

loss of the normal fat plane anterior and lateral to the left psoas muscle.

The diagnosis of a ruptured AAA should be considered in elderly patients that present to the

emergency room hemodynamically stable with abdominal or back pain. Admittedly, the differential

diagnosis for abdominal or back pain in this patient population is extensive, and the incidence of a

ruptured AAA is small. An expeditious history and physical examination can usually determine the cause

of the pain. A pulsatile abdominal aortic mass, an unexplained low hematocrit, or hemodynamic

instability before presentation are particularly worrisome and increase the level of suspicion. The

diagnosis of an AAA may be confirmed with a portable abdominal ultrasound in the emergency room.94

Indeed, the current trauma algorithms include abdominal ultrasound as a diagnostic technique for blunt

trauma, and many centers have ultrasound units assigned to the emergency room and personnel who are

2725

appropriately trained. If ultrasound confirms the diagnosis of an aneurysm, further evaluation with CT

should be obtained to rule out rupture. Alternatively, a CT may be obtained as the sole imaging study.

Any findings consistent with a ruptured aneurysm on CT mandate direct transfer to the operating room

and immediate repair. Aggressive fluid resuscitation should be avoided and mild hypotension (i.e.,

systolic pressure >80 mm Hg) tolerated in conscious patients due to the theoretical potential to cause

the aneurysm to rupture into the peritoneal cavity and/or release the tamponade effect of the

retroperitoneal tissue. If an intact aneurysm is found on CT without any suggestion of rupture, the next

logical question is whether the aneurysm is the source of the pain. Symptomatic aneurysms are likely

associated with an increased risk of rupture although the natural history remains poorly defined.

Patients with symptomatic/intact aneurysms ≥5 cm in diameter should be admitted to a monitored

setting and scheduled for urgent operative repair, usually the following day, provided no alternative

causes for the pain are identified. Additional sources of the abdominal pain should be sought in patients

with aneurysms smaller than 4 cm in light of the small rupture risk. The appropriate treatment for

patients with aneurysms 4 to 5 cm is less clear. These aneurysms have the potential to rupture although

the risk is small. It is recommended that these patients be admitted and the source of their pain further

investigated. However, urgent operative repair is recommended if no additional causes are identified.

The role of screening for AAAs in asymptomatic patients has been partially clarified. The United

States Preventative Task Force has issued a position statement advocating a single screening ultrasound

in males 65 to 75 years of age who have a smoking history and selective screening for males without

smoking history.102 These recommendations were based upon the results of a best-evidence systematic

review that identified four population-based randomized controlled trials demonstrating that screening

resulted in a reduction of aneurysm-related mortality.103 Notably, the Preventative Task Force stated

that the literature did not substantiate screening for women even among those who smoke or have a

family history and stated that the harms of screening outweighed the risks for screening women who

have never smoked. Screening for AAAs in this subset of elderly men has been shown to be both cost

effective104 and comparable to other screening programs in adult patients.105 Despite the Preventative

Task Force’s recommendations, screening should likely be extended to other high-risk patient

populations including patients with a first-degree relative with an AAA, evidence of a peripheral artery

aneurysm, and those undergoing evaluation for heart transplantation. Medicare currently pays for a

single screening ultrasound as part of the Welcome to Medicare physical examination for men who have

smoked sometime during their life and for both men and women with a family history of AAAs.

OPERATIVE INDICATIONS

All patients with symptomatic or ruptured AAAs should undergo operative repair unless they have an

underlying medical condition, such as metastatic cancer, that precludes long-term survival or their

quality of life is not sufficient to justify the intervention. The latter situation entails a difficult decision,

but not offering operative repair should be considered in certain cases (e.g., a debilitated, demented

patient in a nursing home) after discussion with the patient if he or she is alert and coherent and with

the patient’s family.

The operative decision-making process for intact/asymptomatic AAAs is a complex one that needs to

be tailored to the individual patient. Indeed, there is no single parameter that merits repair. The

operative indications are contingent upon the size of the aneurysm, life expectancy, comorbidities,

preference, and anatomic configuration. It is important to remember that the repair of an

intact/asymptomatic AAA is a prophylactic operation that represents a balance between the operative

risk and the future risk of rupture with the ultimate treatment goals to prolong life, relieve symptoms,

and prevent rupture.

The diameter of the AAA is the best predictor of rupture as stated above and has been used as the

most common indication for repair. There has been a change in the diameter-based operative criteria

within the past few decades although this has been clarified more recently with level 1 evidence. It is

interesting to note that the diameter threshold for good-risk patients has decreased from 6 cm to as low

as 4 cm with latter recommendation from the guidelines of the national vascular surgical societies.95

Both the UK Small Aneurysm Trial49 and the ADAM Trial35 concluded that it was safe to follow patients

with 4- to 5.5-cm aneurysms and that early operation did not confer any long-term survival benefit. As

noted above, the rupture risk for patients in the surveillance group was <1%/yr. It is important to note

that more than 60% of the patients in both studies ultimately underwent operative repair despite their

initial randomization. A longer-term follow-up study from the UK Small Aneurysm Trial extending to 12

2726

years did not demonstrate a survival benefit for the patients assigned to early surgery.106 However, it is

important to note that almost all of the patients that survived ultimately required repair since their

aneurysms continued to grow and exceed the 5.5-cm threshold. Indeed, the relevant question may not

be whether patients with small aneurysm need to be repaired, but rather when they need to be repaired.

In a separate publication from the UK Small Aneurysm Trial, Brown et al.50 reported that the rupture

risk for women was over 4-fold higher, as noted above, suggesting that the 5.5-cm diameter threshold

for repair may be too high for women. The proponents of smaller diameter-based thresholds for repair

(i.e., <5.5 cm) have justified their approach stating that even small aneurysms rupture, aneurysms

continue to increase in diameter and will likely need to be repaired, the patients’ medical conditions

will likely deteriorate with age, and the operative mortality/morbidity rate for small aneurysms may be

less. Although the level 1 evidence does not support this lower threshold, it is important to note that the

size discrepancy between a 5.2-cm and a 5.5-cm aneurysm is very small and likely within the resolution

of the imaging study.

The presence of medical comorbidities predictably impacts the perioperative mortality rate and

threshold for repair. Steyerberg et al.107 identified several independent risk factors for operative

mortality during open repair, including renal insufficiency (creatinine >1.8 mg/dL, congestive heart

failure, ECG ischemia, pulmonary dysfunction, older age, and female gender) and these have remained

consistent throughout the literature. Similarly, Beck et al.72 developed a predictive model for both open

and endovascular repair using a prospective registry from the Vascular Study Group of New England.

They reported that chronic obstructive pulmonary disease, suprarenal aortic clamp, renal insufficiency

and advanced age (≥70) were predictive of mortality at 1 year after open repair with the mortality

ranging from 1% to 67% depending upon the number of risk factors. Congestive heart failure and larger

aneurysm diameter (≥6.5 cm) were the only predictive factors after endovascular repair with the

mortality ranging from 4% to 23%. The consistent, dramatic impact of renal insufficiency was further

emphasized by a national series that reported a 9-fold increase in mortality. Notably, the estimated

glomerular filtration rate may be a better index of renal function than serum creatinine and, therefore,

likely a better predictor of adverse outcome. Life expectancy is inseparable from comorbidities, but it

should be emphasized that the average life expectancy for a 60-year-old and an 85-year-old man in the

United States is 18 and 5 years, respectively.108

Patient preference should be factored into the operative decision process. Although the level 1

evidence suggests that it is safe to follow AAAs until they reach the 5.5-cm threshold, patients may not

be willing to accept this small, finite risk and desire to have their aneurysm repaired a lower threshold.

Indeed, patients often echo the justification for early repair proposed by surgeons.

The anatomic configuration of the aneurysm and/or the associated structures should factor into the

operative decision process as well. Any technical factors that complicate the repair likely increase the

perioperative mortality/morbidity including the need for suprarenal clamp application due to the

obligatory renal/visceral ischemia, venous anomalies (e.g., left-sided vena cava), renal anomalies (e.g.,

horseshoe kidney), and inflammatory aneurysms. Admittedly, many of these technical concerns are

relevant only to the open approach and can be overcome/avoided by endovascular repair provided that

it is an option from an anatomic standpoint. Anatomic concerns relevant to endovascular repair include

continued aneurysm degeneration of the aortic neck or iliac arteries that may make standard infrarenal

endograft repair more difficult or impossible unless early repair is undertaken.

The introduction of the endovascular approach has challenged the operative indications for

intact/asymptomatic aneurysms. Indeed, the significant decrease in the perioperative mortality rate

reported in both the DREAM109 and EVAR Trials

79 appear to justify lowering the threshold. However, it

is important to note that the rupture rate for aneurysms less than 5.5 cm in the UK Small Aneurysm49

and ADAM110 Trials was <1%/yr which is still lower than the perioperative mortality rate for

endovascular repair reported from DREAM,109 EVAR,79 and most of the national databases.73,74,111

Similarly, Finlayson et al.112 used a decision analysis model to determine the optimal diameter for open

and EVAR and concluded that the endovascular approach lowers the operative threshold only for older

patients in poor health.

The Joint Council of the American Association for Vascular Surgery and the Society for Vascular

Surgery have released updated guidelines for the treatment of patients with AAAs that address the

concerns highlighted above.48 They recommend that a diameter of 5.5 cm is an appropriate threshold

for repair in the “average patient” with an intact infrarenal aneurysm, but emphasize the importance of

individualizing each case. They state that rapid aneurysm expansion (>1 cm/yr), symptoms related to

the aneurysm, and female gender merit repair at a smaller diameter while consideration should be given

2727

to earlier repair in young patients provided that the operative mortality rate is acceptable. Furthermore,

they recommend that a larger diameter threshold is appropriate in higher risk patients and emphasize

that there does not appear to be any justification to alter the operative threshold for the endovascular

approach. A reasonable approach, and one that we have adopted in our own practice, is to use 5.5 cm as

a threshold for repair in men and 5 cm for women.

Patients that do not meet the threshold for operative repair should be followed closely. It is important

to educate the patients about their underlying disease process and emphasize the importance of longterm follow-up. Notably, Valentine et al.113 reported that 32% of patients with small aneurysms

managed by “watchful waiting” were noncompliant with their follow-up plan. Furthermore, it is

important to counsel patients about the presence of symptoms associated with rupture and the

importance of seeking urgent medical attention. Guidelines have suggested that patients with aneurysms

<3 cm in diameter should be re-imaged at 5 years while those with between 3 and 3.4 cm should be reimaged at 3 years and those between 3.5 and 3.9 cm should be re-imaged at 1 year.114 Aneurysms >4

cm should likely be re-imaged every 6 months. As noted above, abdominal ultrasound is likely the most

appropriate imaging study for aneurysms <4 cm with CT more appropriate above that threshold. It is

important to note that up to 50% of the patients deemed a prohibitive operative risk and not offered

elective repair will ultimately die from a ruptured aneurysm.115–119 These patients who are not

candidates for elective repair should not be offered emergent repair in the event that their aneurysm

ruptures or becomes symptomatic. Patients and families should be counseled on this matter

preemptively to minimize difficulty and inform decisions when rupture occurs.

CHOICE OF OPEN OR ENDOVASCULAR REPAIR

After the decision to recommend operative repair has been made, the technique for repair needs to be

determined. Admittedly, these decisions are somewhat interrelated since the decision to recommend

operative repair in certain subsets of patients is oftentimes contingent upon whether they are candidates

for the endovascular approach. The past two decades have witnessed a rapid evolution of the

endovascular technique, and, indeed, this evolution has helped define our discipline. It has been clearly

demonstrated that the technical success rates for endovascular graft repair are excellent and the need

for intraoperative conversion to open repair negligible. The perioperative events and mid-term

outcomes have been defined by level-1 evidence. Many of the technical limitations inherent to the

earlier endovascular devices and anatomic limitations have been overcome. Despite the lack of

definitive long-term outcome data, the endovascular approach for treatment of AAAs has been widely

applied. Indeed, the endovascular approach eclipsed open repair in the United States in 2005 and recent

data shows that 75% or more aneurysms are repaired in this manner.120 The choice of open or

endovascular repair is complicated and contingent upon several factors including feasibility, outcome,

comorbidities, compliance, cost, and preference. It is imperative that these issues, including their

respective advantages/disadvantages or strengths/weakness, be addressed with the patients during the

decision process to ensure proper informed consent.

The initial determinant of the approach is the anatomic configuration of the aorta, the aneurysm, and

the access vessels. The commercially available endovascular devices come in a finite range of sizes and,

thus, are suitable only if specific anatomic conditions are satisfied. Although the number of available

devices and their specific characteristics are constantly evolving, the “generic” endograft consists of a

fabric graft (i.e., polyester or ePTFE) and a metallic endo/exoskeleton (i.e., stainless steel or nitinol)

that facilitates proximal/distal fixation by the radial force of the stent (Fig. 96-7). In some devices,

proximal fixation is augmented by the presence of suprarenal hooks. The “generic” devices are modular

and consist of either two (main body and contralateral iliac limb) or three (main body, contralateral

iliac limb, ipsilateral iliac limb) components with a variety of additional ancillary pieces that allow

proximal or distal extensions at the aortic and iliac ends, respectively. The initial experience with

aortoaortic or “tube graft” configurations were unsuccessful due to problems with the distal landing site

at the aortic bifurcation and have been abandoned. Indeed, the current strategy is to seat the proximal

component of the bifurcated system as close to the lowest renal artery as possible and the distal

components as close to the iliac bifurcation as possible to improve immediate seal and fixation and

decrease the potential for later aneurysm degeneration at or adjacent to seal sites.

2728

Figure 96-7. The current commercially available infrarenal endografts in the United States are shown: Cook Zenith (A); Medtronic

Endurant (B); Trivascular Ovation (C); Gore Excluder (D); Endologix Powerlink (E); Lombard Aorfix (F). These are modular

devices consisting of a main body, iliac limbs/extensions and main body extensions. Note the common theme of bilateral iliac

limbs and a main body. There are many differences between these endografts, which make them each uniquely suited for some

patients. On the top row (A,B,C), the devices all utilize a bare suprarenal stent construct to facilitate fixation. On the lower row

(D,E,F), the devices utilize active fixation with hooks (D,F) or anatomic fixation at the aortic bifurcation (E).

Although there is some variability among the commercially available devices in terms of their specific

sizes and anatomic constraints, the general anatomic requirements are somewhat similar. The infrarenal

abdominal aorta must have a suitable, nonaneurysmal landing zone for the endograft that measures

≥10 to 15 mm in length and ≥17 to 19 mm, but ≤32 mm in diameter (ranges reflect differences

between the commercial devices). Furthermore, the proximal neck angle should be ≤60 degrees for

most devices (≤75 to 90 for some newer devices), as measured by the intersection of the centerline of

the infrarenal aorta at the landing zone site and the centerline of the aneurysm through the aortic

bifurcation. Newer devices do allow for more neck angulation, but the operating surgeon should keep in

mind that more infrarenal neck may be required in more severely angulated necks to allow for

appropriate seal and fixation of the device. The infrarenal neck should be relatively free of thrombus

and calcification to facilitate a seal at the implantation site. It is notable that neck length requirements

were initially ≥1 cm with the first generation of devices, which was increased to ≥1.5 cm with later

generations, and now has again been decreased to >1 cm with some of the most recent devices. Indeed,

the longer the infrarenal neck length and, therefore, the longer the device seal zone, the better. The

iliac artery should have a suitable landing zone ≥20 mm with an associated diameter between 7 and 20

mm to facilitate both anchoring the graft and passing the main device into the aorta. The distal landing

zone for the iliac limbs is usually in the common iliac artery although the anatomic constraints with

regards to the size of the access vessels and the introduction of the devices are relevant for both the

common and external iliac vessels.

The percentage of patients that are anatomically suitable for an endograft remains unresolved and is

2729