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Chapter 6 Patient Selection Criteria for Endovascular Aortic Aneurysm Repair 119
130 . Drury DD , Michaels JA , Jones L , Ayiku L . Systematic review of recent evidence
for the safety and efficacy of elective endovascular repair in the management of
infrarenal abdominal aortic aneurysm . Br J Surg 2005 ; 92 (8) : 937 – 46 .
131 . Hayter CC , Bradshaw SR , Allen RJ , Guduguntla M , Hardman DTA . Follow-up
costs increase the cost disparity between endovascular and open abdominal aortic
aneurysm repair . Journal of vascular surgery 2005 ; 42 (5) : 912 – 8 .
132 . Michaels JJ , Drury D , Thomas SM . Cost-effectiveness of endovascular abdominal
aortic aneurysm repair . Br J Surg 2005 ; 92 (8) : 960 – 7 .
133 . Velazquez OO , Larson RA , Baum RA , et al. Gender-related differences in infrar-
enal aortic aneurysm morphologic features: Issues relevant to Ancure and Talent
endografts . J Vasc Surg 2001 ; 33 (2) : S77 – S84 .
134 . Zannetti SS , De Rango P , Parlani G , Verzini F , Maselli A , Cao P . Endovascular
abdominal aortic aneurysm repair in high-risk patients: A single centre experi-
ence . Eur J Vasc Endovasc Surg 2001 ; 21 (4) : 334 – 8 .
135 . Schermerhorn ML , Cronenwett JL . Abdominal aortic aneurysm, Chapter 21 .
In Cronenwett and Rutherford Eds., Decision Making in Vascular Surgery .
Philadelphia, PA : W.B. Saunders Co. , 2001 .
https://t.me/med1917
Abstract Endovascular repair of abdominal aortic aneurysm has evolved
dramatically during the last 15 years. From initially a promising experimental
technique, applicable only to a minority of patients with aortic aneurysms, to cur-
rently a widespread technique that is used in more than one half of patients treated
for aortic aneurysm. This chapter presents the current status of this treatment
modality for abdominal aortic aneurysm.
Keywords EVAR , EVAR mortality/morbidity , Stent graft trials , AAA , Zenith
endograft , Aneurx trial , DREAM trial , Stent graft durability
Introduction
Abdominal aortic aneurysm (AAA) is a common condition, occurring in
approximately 1 in 20 older men who have ever smoked.
1
Population-based
studies indicate that AAA is responsible for about 1.7% of deaths among
adults aged 65–74 years. The natural history of AAA is characterized by
progressive expansion and rupture with the rate of rupture and death for aneu-
rysms > 6 cm in diameter exceeding 40% within 3 years of the initial diagnosis.
2
More than 15,000 deaths from aneurysm rupture occur annually in the US
with an overall mortality rate for ruptured AAA approaching 90%. Rupture
of these aneurysms has a mortality rate of 80%
3
and causes 9000 deaths per
year in the US.
4
To prevent rupture, elective repair of an AAA is performed
in nearly 40,000 patients each year in the US. Over the last 50 years, AAAs
have been treated with prophylactic open surgical repair, a major surgical
procedure consisting of laparotomy and cross-clamping of the aorta. The first
resection and graft replacement of an AAA was performed in 1951 by Dubost
et al.
5
The open repair is associated with a 30-day mortality of 4–12%
6
but
the grafts are generally durable and last over 20 years. However, patients with
aneurysms are generally elderly and often have significant comorbid medical
conditions that increase the operative risks. More recently, endovascular repair
was developed to provide a less-invasive alternative. In 1990, Juan C. Parodi
Chapter 7
Endovascular Repair of Abdominal
Aortic Aneurysms
Sheela T. Patel and Juan C. Parodi
G. Upchurch and E. Criado (eds.) Aortic Aneurysms, Contemporary Cardiology
DOI: 10.1007/978-1-60327-204-9_7, © Humana Press, a part of
Springer Science + Business Media, LLC 2009
121
https://t.me/med1917
122 S.T. Patel and J.C. Parodi
performed the first endovascular AAA repair in Buenos Aires, thus heralding
a new era in the treatment. According to national hospital databases, there has
been a 600% increase in the annual number of endovascular aortic aneurysm
repair (EVAR) procedures performed in the US since 2000, comprising nearly
half of all aneurysm repairs.
7
Continuing technological advances have made
EVAR the first-line therapy for AAA in anatomically suitable patients. EVAR
has become a mainstay in the arsenal of the vascular surgeon. This procedure
has permitted physicians to treat a high-risk older group of patients that in the
past would have been excluded from open aneurysm repair. In the last 5 years,
there have been more than 30,000 endovascular graft devices implanted annually
in patients to treat AAA size with favorable results.
Several studies have demonstrated decreased morbidity and mortality
following endovascular repair of AAA. Other advantages include decreased
blood loss, decreased transfusion requirements, decreased ileus, and quicker
return to baseline functional status. This procedure can be performed in higher-risk
patients for whom an open repair would not have been a viable option.
Patient Selection for Endovascular Repair
Currently EVAR is an FDA-approved alternative for open AAA repair. Patients
with large (>5–5.5 cm) aneurysms or patients with smaller size (4–5 cm)
aneurysms but rapidly enlarging should be considered for repair. Although
many published series for endovascular AAA repair include patients with
small AAA, findings of randomized clinical trials showed that, compared with
surveillance by CT or ultrasonography, a strategy of immediate repair did not
improve survival among patients who had AAA of 4–5.4 cm in diameter.
8,
9
In recent years, the number of patients treated with EVAR has steadily risen
as a result of increased physician experience, availability of new and more
versatile devices, and improvements in noninvasive imaging techniques. Some
consider 25–30% of all treatable AAA to be eligible whereas others report that
up to 80% can be treated.
10
When considering EVAR, the patient’s age, comorbid conditions, and
life expectancy and anatomy should be considered. The primary factors that
determine feasibility of endovascular repair are the diameter and length of the
proximal neck of the aneurysm, the tortuosity of the aorta, and the anatomy of
the iliac arteries. Unfavorable neck anatomy is the primary factor for exclu-
sion from endovascular repair. If the angle between the neck of the aneurysm
and the aorta is excessive, the graft may be displaced from its intended posi-
tion with a subsequent leak at the attachment site. If the common iliac arteries
are too large, the limb of the stent may not be well apposed to the wall of the
artery, and a leak at the attachment site will result. Relative anatomic con-
traindications for EVAR include proximal neck < 15 mm, infrarenal aortic
diameter > 26 mm, external iliac diameter < 7 mm or > 16 mm, and bilateral
internal and external iliac aneurysms.
Patients considered for EVAR must undergo preoperative imaging to
assess anatomy. CT with thin cuts of the abdomen and pelvis and subsequent
reconstruction is used for operative planning including device selection and
sizing. Anatomic and technical criteria must be fulfilled to enable EVAR to
be performed successfully. Inadequate proximal neck anatomy is one of the
most common reasons why patients are found unsuitable for EVAR. Ideally,
an infrarenal neck length of at least 10–15 mm from the lowest renal artery
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Chapter 7 Endovascular Repair of Abdominal Aortic Aneurysms 123
is required for adequate proximal device fixation. Graft diameter usually is
usually oversized by approximately 10–15% to ensure adequate radial forces
to prevent migration and allow good apposition to the aortic wall. Current
commercially available devices range up to 32 mm in diameter, therefore an
aortic neck diameter £ 28 mm is necessary for adequate fixation. Treatment of
aneurysms with larger infrarenal neck diameters may be possible with larger
devices. An ideal neck should have minimal thrombus and calcification so
that proximal fixation is easier and decrease the risk for migration or type
I endoleaks. Aortic neck angulation greater than 60° can lead to imprecise
proximal placement with kinking and poor fixation and is considered a relative
contraindication to EVAR. Treatment of aneurysms with neck angle greater
than 60° is determined by the conformability of the specific device.
Patients with a juxtarneal or suprarenal AAA are not amenable to EVAR
with devices currently available in the US. With the development of branched
and fenestrated grafts, full endoluminal aortic coverage can be achieved with
preservation of visceral and pelvic perfusion. Branched graft technology is
currently in use in some European countries and awaits FDA approval in the
US, pending the completion of ongoing device-specific US clinical trials.
The guidelines of a subcommittee of the American Association for Vascular
Surgery and the SVS concluded that EVAR should be limited to large aneu-
rysms with suitable anatomy in patients unfit for open surgery.
11
A decision-
model analysis of data from the European Collaborators on Stent Graft
Techniques for Abdominal Aortic Aneurysm Repair (EUROSTAR) registry
also suggested that EVAR is preferred for older patients with higher operative
risk, whereas open repair is preferred for younger patients with low operative
risk.
12
These positions reflect the lack of mortality benefit for EVAR and con-
cerns over its durability.
Stent Graft Trials
After the initial success of homemade endovascular stent grafts, commercially
manufactured devices were developed and are currently increasingly utilized
as a minimally invasive alternative to open repair. Four have received approval
from the US FDA: AneuRx (Medtronic, Inc., Minneapolis, MN), Excluder
(W.L. Gore and Associates, Flagstaff, AZ), Zenith (Cook, Inc., Bloomington,
IN), PowerLink (Endologix, Irvine, CA) and Talent (Medtronic). Other devices
that have received approval for use in the European Union or Canada or are at
the clinical trial stage in the US include Fortron (Cordis, Inc., Sommerville, NJ),
and Anaconda (Sulzer Vascutek, Austin, TX). The majority of these devices are
modular units and have available separate extension segments for each iliac seg-
ment, allowing for more customization to fit the patient’s particular anatomy.
Zenith Trial Overview
The Zenith endograft (Cook, Inc., Bloomington, Indiana) approved by the FDA
in 2003 is a supported, bifurcated, self-expandable stent graft with multiple
stainless steel Z stents placed inside the graft. It attaches to the vessel wall with
barbs. It has a proximal noncovered stent for suprarenal fixation to prevent
migration and enhance graft-to-vessel attachment. FDA approval was based
on a comparison between four groups of patients: a control group, a standard-
risk group, a high-risk group, and roll-in group. A total of 352 patients were
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124 S.T. Patel and J.C. Parodi
prospectively enrolled. Eighty concurrent surgical controls were enrolled
with the intent of comparing them to the standard repair endovascular group.
Significantly decreased cardiac, pulmonary, and renal morbidities were noted
at 30 days in the endograft group. EVAR patients had fewer transfusion
requirements, diminished blood loss, shorter hospital stay, decreased intensive
care unit (ICU) stay, and quicker return to daily activities. Kaplan-Meier analysis
demonstrated no difference in all-cause mortality and aneurysm-related death
between the standard-risk EVAR group and the surgical control group. No
acute conversions occurred. Three late conversions to open surgery were
reported. Migration was not seen in any patients at 1 year. The majority of
aneurysms were smaller in diameter at 1 and 2 years of follow-up. The Zenith
endograft demonstrated a reduction in morbidity, mortality, and recovery
time, as well as a high rate of aneurysm shrinkage.
13,
14
Procedural morbid-
ity was also significantly lower for patients treated with endovascular grafts.
The endoleak rate was 4.9% at 12 months in the standard-risk group.
Excluder Trial Overview
The Excluder (W.L. Gore and Associates, Inc., Flagstaff, AZ) was approved
by the FDA in 2002. It is a bifurcated endograft with an outer self-expanding
nitinol support structure covered with ePTFE . The device is wrapped around
the delivery system and tied with a PTFE thread. Two-year outcome data
from the pivotal US multicenter, prospective Gore Excluder trial showed that
patients treated with the Excluder endograft had less blood loss, required
fewer transfusions, and had faster inpatient recovery compared to those treated
with open repair.
15
Early major adverse events were reduced significantly in
patients treated with the endograft (14% vs 57%, p < .0001) and this persisted
at 2 years. There was no difference in overall survival rate. Endoleak occurred
in 20%, persistent aneurysm growth in 14%. Overall, there was a 7% annual
reintervention rate in the endograft group in the first 2 years. However, at
3-year follow-up, the investigators noted pressurization or increase in the
aneurysm size in the absence of leaks in up to 20% of patients. The thin ePTFE
material with high porosity used in the first-generation device was felt to be
responsible for the endotension. Therefore, the device was modified and a low
permeability design was introduced in 2004. The new material is engineered to
reduce the potential for serous fluid movement through the graft wall.
AneuRx Trial Overview
The AneuRx (Medtronic, Inc., Minneapolis, MN) was the first modular device
approved by the FDA in 1999. The modular system consists of a main bifurcated
segment and a contralateral iliac leg. The initial multicenter study involved 250
patients with infrarenal aneurysms.
16
A total of 190 patients underwent endovas-
cular repair using AneuRx and 60 underwent open surgical repair. During an
18-month period, there was no significant difference in mortality rates between
the groups but patients who underwent EVAR had significant reduction in blood
loss and days in the ICU. The major morbidity rate was reduced from 23% in the
surgery group to 12% in the endovascular group ( p < .05). Pooled data from the
US Phase I, Phase II, and Phase III clinical trials of 1192 patients treated with
AneuRx over 3 years of follow-up showed that the device has markedly reduced
the risk of aneurysm rupture while eliminating the need for open surgery in 98%
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Chapter 7 Endovascular Repair of Abdominal Aortic Aneurysms 125
of patients at 1 year and 93% of patients at 3 years. The overall patient survival
rate was 93% at 1 year and 86% at 3 years.
17
Endologix Trial Overview
The Endologix PowerLink system is a one-piece bifurcated graft composed
of PTFE supported by nitinol. A prospective multicenter trial using this
device was conducted at 15 sites. Between 2000 and 2003, 258 patients were
enrolled. Patients treated with this device had significantly decreased periop-
erative mortality, blood loss, operative time, ICU, and hospital stay compared
to the open surgery control group. There were no reported type I, III, or IV
endoleaks at the 48-month follow-up, nor were there any ruptures, graft fabric
defects, or stent wire fractures. The authors concluded that the PowerLink
device is safe and protects treated patients from rupture, with longer follow-up
needed to determine durability.
Registries
The two most important registries are the UK registry for Endovascular
Treatment for Aneurysm (RETA) based in Sheffield, England, and the EUROSTAR
registry based in Holland. These registries, although voluntary, have provided
important information on EVAR, and data from the RETA registry was used
in the design of the UK EVAR trials. Open audit in the form of voluntary
registries is a useful tool for clinical evaluation of new technologies but do not
replace randomized controlled trials in that they are incomplete and open to
data entry bias.
The RETA registry was set up in 1996 to audit EVAR deployments within
the UK. It contains retrospective and prospective data on 1823 procedures.
However, it is voluntary and audited in an open fashion, possibly leading to
selection bias. The midterm results from the RETA registry show that at 30
days, 5.8% of patients had died. Postprocedural complications within 30 days
occurred in 27.8% of cases and 6.1% had persistent endoleaks. Mortality in the
first year was 11%, and 10% per year thereafter up to 5 years. Complications
related to the device and aneurysm occurred at a rate of approximately 15%
per year (secondary endoleaks, graft migration, kinking, limb occlusion).
The EUROSTAR registry was launched in 1996 as a prospective audit of
EVAR performance across 135 centers in 18 European countries. This registry
is also voluntary but is the largest registry of devices in Europe. Over one thou-
sand patients have been followed up for more than 5 years. Life table analysis
shows a 5-year cumulative survival of 79.2%, a secondary intervention rate of
76.3%, and freedom from aneurysm rupture of 98.6%. This registry concluded
that EVAR in high-risk patients may be justified if the patient’s life expectancy
is greater than 1 year, and that the medium-term outcome is significantly better
in patients treated for small aneurysms.
The Lifeline Registry of Endovascular Aneurysm repair was established by
the Society for vascular surgery in 1998 to evaluate the long-term outcome
of EVAR using FDA-approved devices. This registry contains data on 2664
EVAR patients and 334 open surgical control patients collected under four
multicenter IDE clinical trials (AnCure, AneuRx, Excluder, PowerLink).
There was no difference in 30-day mortality between EVAR (1.7%) and open
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126 S.T. Patel and J.C. Parodi
surgery (1.4%), and there was no difference in survival at 4 years between
EVAR (74%) and surgery (71%). The EVAR group had significantly older and
sicker patients than the open surgery group and included patients at high risk
for open surgery. Kaplan-Meier analysis revealed a 1.3% cumulative risk of
rupture at 5 years among 2664 EVAR patients. This is lower than the 1% per
year rupture rate in patients with small aneurysms (<5.5 cm) followed in the
UK Small Aneurysm Trial Participants.
8,
9
Randomized Trials of Open and Endovascular AAA Repair
EVAR Clinical Trial Overview
Since the early feasibility trials of EVAR, multiple trials have been performed
comparing the results of EVAR with conventional open repair.
16,
18–
21
These trials
were successful in confirming the perceived perioperative advantages of EVAR
but were limited by their designs with regards to patient standardization and
randomization. More recently, two large randomized trials that enrolled suitable
candidates for either open repair or EVAR have been performed, including the
Dutch Randomized Endovascular Aneurysm Management (DREAM) trial in
the Netherlands and the Endovascular Aneurysm Repair Versus Open Repair
(EVAR) trial in the UK. The European randomized trials have provided level-1
evidence to show that EVAR is more effective in preventing aneurysm-related
death than conventional open surgery. The perioperative results of both DREAM
trial and EVAR 1 trial confirmed the advantages of the less-invasive nature of
EVAR.
22,
23
In both trials, operative time, transfusion requirements, length of ICU
stay, and overall length of stay were significantly less for patients undergoing
EVAR. Furthermore, perioperative mortality was significantly lower after EVAR
when compared with open repair in both trials. In addition to these results favor-
ing EVAR, the perioperative EVAR 1 trial data, however, showed what has been
perceived as one of the shortcomings of EVAR, a significantly higher rate of
secondary interventions compared with open repair (9.8% vs 5.8%).
Although these randomized trials successfully showed the perioperative
advantages of EVAR over open repair, there is still debate regarding the mid-
term and long-term advantages of EVAR. The midterm data from the DREAM
trial obtained at the 2-year follow-up appear to suggest that the initial periop-
erative advantages of EVAR may not be maintained over time.
24
The overall
survival rate 2 years after randomization was 89.7% for patients undergoing
EVAR compared with 89.6% for those undergoing open repair. The midterm
data from EVAR trial 1 drew similar conclusions.
25
All-cause mortality 4
years after randomization was similar between patients undergoing EVAR
and patients undergoing open repair at approximately 28%. Additionally, both
studies showed significantly higher rates of reintervention after EVAR com-
pared with open repair (20% vs 6% in EVAR 1 and a nearly three times higher
rate in the DREAM trial). Given the short-term and midterm data produced
by these trials, a question remains with regard to the long-term advantages of
EVAR over open surgery. In particular, the questions of whether survival will
be different over the long term compared with patients undergoing open repair
and if EVAR will prove to be cost-effective given the higher rates of reinter-
vention. Longer-term data and cost analysis are necessary to help physicians
determine which patients will most benefit from EVAR.
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Chapter 7 Endovascular Repair of Abdominal Aortic Aneurysms 127
There are two additional ongoing trials of open repair versus EVAR that have
not yet reported results: the Veteran Affairs Open versus Endovascular Repair
(OVER) trial for abdominal aortic aneurysms and the French Aneurisme de
l’aorte abdominale: Chirurgie versus Endoprosthese (ACE) trial.
A recent systematic review of four trials including over 1500 patients com-
paring open repair with endovascular repair
26
concluded that EVAR reduced
30-day mortality but not the 4-year mortality.
The DREAM Trial
The DREAM trial was a multicenter randomized trial of EVAR versus open
surgery in which 351 patients were randomized with AAAs larger than 5.5 cm.
Patients were enrolled if considered fit for open surgery and had suitable anatomy
for EVAR. Initial results were reported in 2004
23
and revealed a 30-day
mortality rate in favor of EVAR (1.2% EVAR, 4.6% OR). The combined rate
of operative mortality and severe complications at 30 days was 9.8% for open
and 4.7% for EVAR. At 2 years, the cumulative survival rates were 89.6% for
open versus 89.7% for EVAR. The cumulative rates of aneurysm-related death
were 5.7% and 2.1% for open and EVAR, respectively. Two-year follow-up
results were reported in 2005
24
and demonstrated that all-cause mortality
was not significantly different between the two groups (20.4% EVAR, 20.3%
open). Although a trend toward reduced aneurysm-related death was noted
for EVAR (2.1% EVAR, 5.7% open), this difference was not statistically dif-
ferent. Quality of life improved initially for EVAR, but after 6 months, it was
equivalent for both groups. The authors concluded that the initial mortality
advantage of EVAR over open was lost by 1 year because of nonaneurysm-
related deaths.
The EVAR Trials
The UK EVAR trials were initiated in 1999.
27
EVAR 1 randomized suitable
patients to either EVAR or open repair. Patients who were unfit to undergo
open repair due to significant comorbidity were entered into the EVAR 2
trial. This randomized patients to either EVAR and best medical treatment or
best medical treatment alone. Both EVAR trials were limited by long delays
between randomization and treatment.
The EVAR 1 trial randomized 1082 patients over 60 years of age with an
aneurysm of 5.5 cm or greater to either open repair or EVAR. A total of 512
patients in the EVAR group received their intended elective treatment com-
pared with 496 in the open repair group. Thirty-day and in-hospital mortality
were 2/3 lower in the EVAR group than in the open group (1.7% vs 4.7%,
p = .016).
22
By 4 years, all-cause mortality had leveled off at about 28%
for both groups.
28
However, there was a persistent difference in aneurysm-
related mortality, 4% for the EVAR group and 7% for the open repair group.
The overall rate of complications and reinterventions appeared to diverge
between groups over time. Thirty-five percent of all patients receiving EVAR
reported one or more postoperative complications, of whom 44% required a
secondary intervention. In addition, there were 14 conversions to open repair
following EVAR deployment. In contrast, complications and reinterventions
were rare in open repair patients. The 30-day mortality for EVAR was 1.7%
compared with 4.7% for open repair ( p = .007). This mortality was lower than
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128 S.T. Patel and J.C. Parodi
that reported by the RETA and EUROSTAR registries, perhaps because the
patients randomized in EVAR 1 were those deemed fit to have an open repair
compared to the registry data which included unfit patients. The EVAR 1 trial
30-day results reported that secondary procedures were necessary in 9.8%
of EVAR patients compared with 5.8% in the open repair group. Endoleaks
needed treatment in 3.4% of EVAR patients and ten patients required conver-
sion to open repair intraoperatively. Reinterventions were required in three
times as many patients who had EVAR, exceeding 20% at 4 years.
The EVAR 2 trial enrolled 338 patients aged more than 60 years who had
aneurysm of at least 5.5 cm in diameter and who met high-surgical risk crite-
ria for open repair due to cardiac, pulmonary, or renal comorbidities. Patients
were randomized to EVAR or no intervention. The 30-day mortality for EVAR
was 9%. AAA-related mortality at 4 years was 14% for EVAR and 19% for
no intervention. Overall, 4-year survival was only 34% in EVAR and 38% in
the no-intervention group. The authors concluded that EVAR “is not a safe
procedure in such high-risk patients.” High crossover and procedural mortality
rates have led to controversy regarding the validity of this trial. It is uncertain
whether these rates could be improved in another trial or whether they reflect
the inherent difficulties of managing these sick patients. Twenty-seven percent
of patients crossed over from nonoperative to EVAR and these patients had a
lower procedure mortality from EVAR than those originally assigned to it (2%
vs 9%). These 47 cases and the exclusion of 14 patients dying while waiting
for EVAR appear to confer a survival advantage to those receiving EVAR over
those receiving no treatment in a post hoc analysis, but the per protocol analy-
sis did not show a significant difference in either all-cause or aneurysm-related
mortality. Outcomes of the EVAR 2 trial have not settled the option for high
surgical risk patients.
The trial used a “pragmatism rule” in which internists, cardiologists, radi-
ologists, or surgeons were required to make a determination of whether the
patient was unfit for surgery. The lack of objectivity inherent to this pragma-
tism is verified by the fact that a significant number of patients (47) form the
surveillance arm crossed over to EVAR with a mortality of only 2%. The high-
risk patient population likely lacks uniformity because no standard, objective
criteria were used in making this determination.
Sicard et al.
29
identified high-risk patients (565 EVAR and 61 open) in
five US multicenter controlled IDE clinical trials. Application of the EVAR 2
high-risk criteria to these trial data identified 565 patients who were certainly
more ill than the 1651 normal-risk patients (4-year mortality: 44% high risk,
21% normal risk). High-risk was defined to match EVAR 2 and includes age
60 years or more with aneurysm size ≥ 5.5 cm and at least one cardiac, pulmo-
nary, or renal comorbidity. The 30-day operative mortality was 2.9% in EVAR
versus 5.1% in open ( p = .32). Overall survival at 4 years after EVAR was
56% versus 66% in open ( p = .23). The AAA-related death at 1 year was 3%
for EVAR and 5.1% for open ( p = .37). After treatment, EVAR successfully
prevented rupture in 99.5% at 1 year and in 97.2% at 4 years.
Despite fitting the EVAR 2 definition of high risk, the US IDE trial mortality
compares favorable with EVAR 2 in short-term (30-day mortality: 2.9% US
IDE vs 9% in EVAR 2) and 4-year (44% US IDE vs 64% EVAR 2) results. They
concluded that EVAR is safe and effective in most patients with advanced age,
large aneurysms, and high-risk medical comorbidities. Sicard concluded that
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Chapter 7 Endovascular Repair of Abdominal Aortic Aneurysms 129
EVAR provides excellent protection from aneurysm rupture and AAA-related
death, with no significant difference from open surgical controls. High-risk
patients found to have an extremely short-life expectancy from nonaneurysmal
disorders may be appropriate candidates for watchful waiting.
Durability
Morphological and structural changes of the endograft leading to device
failure have been reported. These changes include: suture breaks between the
stent and the graft, fracture of the hooks used to anchor the proximal end of
the endograft to the aortic wall, circular and longitudinal stent wire separation,
separation of the connections between wire loops, graft fatigue, device migra-
tion, component separation, endograft, or vessel thrombosis. Most of these
failures manifest with an endoleak.
Endoleak is defined as the incomplete exclusion of the aneurismal sac from
the circulation with persistent perfusion of the aneurysm. Meta-analysis of
23 publications involving 1118 patients with successful EVAR yielded an
endoleak rate of 24%.
30
Of these endoleaks, 66% were present immediately
after stent graft placement and 37% were persistent over time. The clinical
significance of endoleaks and their impact on the natural history of aneurysms
is uncertain and poorly understood. Endoleaks are classified as:
• Type I: from the proximal or distal attachment sites of the graft. Treatment
is usually graft extension.
• Type II: from side-branch vessels (lumbars or inferior mesenteric arteries)
that continue to feed the excluded aneurysm sac; mainly treated with coil
embolization, if necessary.
• Type III: due to fabric tear, modular or graft disconnection, or graft disin-
tegration.
• Type IV: vascular flow caused by the high porosity of the graft, most likely
created by the numerous suture holes holding the graft material to the stent.
• Type V (endotension): growth of the aneurysm sac but reperfusion of the sac
could not be demonstrated.
Repair of Small Aneurysms
Traditional teaching dictates repair for AAAs when they reach a diameter of
5–6 cm. Two randomized prospective trials, the UK Small Aneurysm trial and
the US Veterans Administration (ADAM) trial, compared early surgical repair
with observation.
8,
9
Both trials concluded that there is little benefit from early
open surgical repair of aneurysms 4–5.5 cm. The perioperative complication
rates associated with open surgery were not insignificant for the two trials
(2–6%). The relatively high complication rates associated with open surgery
raise the question of whether a trial of early EVAR versus serial surveil-
lance might demonstrate benefits. The perioperative mortality rate was 1.8%
(22/1193) in the AneuRx databases. EVAR of smaller aneurysms may be safer.
The PIVOTAL trial was designed to assess the merits of early endovascular
repair of infrarenal small AAAs. This multicenter prospective randomized
study will compare EVAR with FDA-approved Medtronic stent grafts with
surveillance every 6 months for management of 4–5 cm AAAs.
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